Unit and method for moving blanks

Abstract

A unit (1) for moving a stack of blanks (100) comprises a support structure (2); a first and a second grasping device (10, 20) fixed and mutually spaced so as to engage the blanks (101) in a first longitudinal portion (PA) and in a second longitudinal portion (PB), the first grasping device (10) comprising a first and a second grasping element (11, 15) wherein at least one of the grasping elements (11, 15) is provided with a first grasping tooth (12, 16) intended to engage a lower surface (S) of the stack of blanks (100); the second grasping device (20) comprising a third and a fourth grasping elements (21, 25) wherein at least one of the grasping elements (21, 25) is provided with a second grasping tooth (22, 26) intended to engage a lower surface (S) of the stack of blanks (100); wherein the first grasping device (10) comprises at least one grasping appendage (30) configured to engage a third longitudinal portion (PC) of the stack of blanks (100) spaced apart along the longitudinal direction (X) from the first longitudinal portion (PA) and the second longitudinal portion (PB) and oscillating with respect to the second longitudinal portion (PB) and / or the first longitudinal portion (PA).

Description

UNIT AND METHOD FOR MOVING BLANKS DESCRIPTION

[0001] The present invention relates to a unit and method for moving blanks intended to form boxes enclosing one or more articles.

[0002] The invention also relates to a packaging apparatus including a unit for moving blanks.

[0003] The present invention also relates to a pick-up head, a machine and a method for picking up and moving a group of articles, preferably a bundle of blanks.

[0004] The invention is applied in units for unpacking and distributing blanks where stacks or bundles of blanks are to be moved to be transported to handling units of the blanks themselves.

[0005] The invention finds preferred but not exclusive application in packaging apparatuses equipped with blank handling units in which blanks are supplied and subsequently folded to form boxes. Therefore, reference will be made below to this field without losing its generality.

[0006] In this description as well as in the accompanying claims, some terms and expressions are deemed to have, unless otherwise expressly indicated, the meaning expressed in the following definitions.

[0007] “Blank” is intended to mean a shaped sheet of suitable material and thickness, adapted to be folded to form a box. Preferably, the blank is made of cardboard. Preferably, the blanks have two substantially planar opposing faces that are substantially larger in size than the thickness of the blanks themselves. Preferably, the blank has a thickness of at least 0.2 mm, more preferably less than 4 mm. In a greatly preferred manner, the blank has a thickness comprised between 0.25 mm and 1 .6 mm, more preferably between 0.3 mm and 1 mm, even more preferably between 0.4 and 0.8 mm.

[0008] A “folding line” of a blank is a predefined line made on the blank, intended to define two panels in the blank, and around which the two panels of the blank are expected to swing relative to each other so as to fold the blank, preferably to form a box. The folding line can be a virtual line even if it is predefined. The folding line is preferably defined by a weakening line obtained on the blank, e.g., a creasing, or an incision ora plurality of aligned holes.

[0009] The term “stack” or “bundle” refers to a plurality of substantially planar objects, in particular blanks placed one on top of the other, or side by side. In particular, a stack (or bundle) of blanks is a set of blanks placed adjacent to each other so that the faces of twoadjacent blanks face each other. In the stack of blanks, the faces of two adjacent blanks may be in contact with each other, or spaced apart. The stack of blanks may be formed by a desired number of blanks. The stack has a surface area in plan corresponding to the outline of the face of the blanks, a number of flanks that depends on the outline of the blanks and a height that depends on the number of blanks forming the stack itself.

[0010] The term “article” means any product which can be packaged in boxes. The articles can have a predefined geometric shape or they can have a variable geometry.

[0011] The term “packaging” one or more articles in a box means obtaining a box containing said one or more articles. Such packaging can be obtained by inserting one or more articles into an already formed box or, preferably, it can be obtained by forming a box around the one or more articles to be contained.

[0012] In general terms, a first element “engages” a second element when the first element touches the second element and is able to at least partially oppose a relative displacement of the first element against the second element.

[0013] In particular, the blank is “engaged” by a component of the movement unit, when the component is in contact with the blank. It should be noted that engagement of the blank does not in itself imply that the blank is engaged for its entire surface by a component of the movement unit, but it is sufficient that there is contact between the component and the blank on a portion of the blank itself.

[0014] In general terms, a first element “retains” a second element when the first element touches the second element and is able to at least partially oppose a relative displacement of the first element against the second element.

[0015] “Box” means any container suitable adapted to hold a plurality of articles for the purpose of their packaging and which is suitable to be made from a blank. The box can be obtained by bending a blank around a mandrel and then fixing the blank at its edges or panels. Preferably, the box has at least one closed contour section, more preferably it is closed laterally around the mandrel while the longitudinal ends are kept open.

[0016] The Applicant has preliminarily observed that the provision of a unit for moving blanks equipped with grasping elements to pick a stack of blanks from a storage unit and feed it to a unit for feeding blanks provides significant advantages in terms of efficiency and speed of movement of the blanks. In fact, the blanks are loaded and accumulated in a storage unit in considerable quantities. A movement unit then takes stacks of blanks from the storage unit formed by a desired number of blanks so that they are suitable to be received by the feeding unit, moves them towards and loads them into a feeding unit.

[0017] However, the Applicant observed that sometimes the blanks are not stably engaged by the grasping elements of the movement unit and tend to move relative to the grasping elements during movement from the storage unit to the feeding unit. The Applicant noted that in some cases blanks are fed incorrectly into the feeding units and that this compromises subsequent processing of the blanks.

[0018] The Applicant also noted that the blanks can sometimes get torn in the step from the movement unit to the feeding unit, which compromises the subsequent use of the blanks.

[0019] The Applicant highlighted the need for a pick-up head, a machine and a method for picking and moving a group of articles that would guarantee high accuracy in positioning the articles in a processing station.

[0020] For this purpose, the Applicant noted that the blanks are loaded into a storage unit from which a handling unit picks up individual stacks of blanks each containing a desired number of blanks. The blanks are loaded onto the storage unit in such a way as to create a stack of blanks consisting of a plurality of blanks placed on top of each other and positioned so that the faces of two adjacent blanks face each other and are in contact with each other. The stack of blanks is usually placed on a storage unit support base so that the face of a blank rests on the support base. The support base is usually horizontally oriented and a lower blank is identified in the stack, i.e. the blank resting on the support base, an upper blank, i.e. the blank at the apex of the stack, a lower surface of the stack, i.e. the face of the lower blank resting on the support base, an upper surface of the stack, i.e. the face of the upper blank set against the support base, and a stack height, defined as the distance between the upper and lower blanks, i.e. the distance between the upper and lower faces of the stack.

[0021] The movement unit usually comprises two pairs of grasping elements spaced along a first direction, referred to hereafter as the longitudinal direction, each pair of grasping elements comprises two grasping elements facing and spaced along a second direction perpendicular to the longitudinal direction, and referred to hereafter as the transverse or grasping direction.

[0022] Each grasping element is configured in the shape of an “L” and comprises a grasping tooth intended to be inserted below the stack of blanks so as to engage the lower surface of the stack of blanks to support the stack of blanks, and an abutment element perpendicular to the grasping tooth and intended to abut a lateral flank of the stack of blanks being removed. In order to pick up the stack of blanks, the movement unit is brought closeto the storage unit and driven in such a way that the grasping teeth are inserted below the lower surface of the stack of blanks and the abutments are brought into contact with the lateral flanks of the stack. In this way, the grasping elements engage the lower surface and side walls of the stack. When the blanks are engaged to the movement unit, the latter is moved to take the blanks from the storage unit and move them to a unit for feeding blanks, or, in general, to desired processing units where the blanks are folded to form boxes.

[0023] Each movement unit therefore comprises four grasping elements that are configured to engage the stack of blanks in four distinct grasping portions and that are positioned in such a way that, when the grasping elements engage the stack, an inner portion corresponding to the area of the blanks interposed between the grasping elements and at least one outer portion of the blanks corresponding to the portion of the blanks arranged outside the grasping elements is defined on the blanks. Usually the grasping elements engage a stack in such a way that at least an external portion of the blanks extending outside the grasping elements along the longitudinal direction is defined.

[0024] The Applicant noted that the grasping elements must be positioned in such a way that they correctly support the stack of blanks and avoid unwanted displacements of the stack during movement.

[0025] The Applicant has found that sometimes stacks of blanks may not be properly engaged by the grasping elements and that this adversely affects the correct movement of the blanks by the movement unit and, above all, the correct handling of blanks in subsequent handling units, promoting tearing of the blanks during pick-up, or incorrect positioning of the blanks on the feeding unit and / or the subsequent processing unit. This generally compromises the quality of the formed boxes. The Applicant also verified that when blanks are not correctly positioned on the movement unit, this can lead to incorrect folding of the blanks in the formation of the box and, consequently, to a decrease in the quality of the boxes produced.

[0026] The Applicant also observed that, especially with stacks of blanks having large faces, external portions of the stack are defined as having considerable dimensions, i.e. significant portions of the stack are arranged outside the grasping elements. This results in the weight of the stack not being optimally distributed on the movement unit and high modulus torques being generated during the movement of the stacks. The Applicant has verified that this causes unwanted displacements of the blanks in relation to the grasping elements and that the blanks may sometimes bend in an undesirable manner during movement with the movement unit. The Applicant noted that this negatively affects thepositioning of the blanks in the feeding unit. The Applicant verified that incorrect positioning or even tearing of the blanks in the feeding unit can occur. This compromises the possibility of using the blanks in subsequent processing units. The Applicant has verified that such damage is particularly evident and / or frequent when the blanks are of limited thickness and strength and as the size and / or number of blanks in the stack increases.

[0027] The Applicant also verified that at times the grasping elements were not able to properly engage the stacks of blanks and that, in some cases, one or more panels of the blanks were not engaged by the grasping elements and tended to oscillate in relation to the adjacent panel, bending under the effect of the weight of the stack of blanks. The Applicant verified that this disadvantage was particularly evident as the number of blanks in the stack being moved by the movement unit and the size of the outer portion, i.e. the portion of the stack outside the grasping elements, increased. Furthermore, the Applicant verified that this disadvantage was more frequent as the thickness of the material of the blanks decreased and / or the flexibility of the material of the blanks increased.

[0028] The Applicant thus envisaged modifying the operations for picking up the stacks of blanks from the storage units by providing a step for checking the position of the grasping elements with respect to the stack of blanks and, if necessary, an adjustment step for adjusting the position of the grasping elements according to the dimensions of the blanks of the stack to be moved, carrying out the control step whenever the handling unit had to engage a new stack of blanks and the adjustment step whenever it was necessary to adjust the position of the grasping elements to suit the shape and size of the stack being moved. However, the Applicant found that this would result in a considerable slowing down of the picking and handling operations of the stacks of blanks, especially whenever there was a change of format of the blanks in the storage unit, or when an adjustment of the grasping elements was necessary.

[0029] The Applicant verified that this solution would have considerably slowed down the operations of picking up the stack of blanks and that these arrangements would in any case not have been sufficient to remedy the drawbacks outlined above as the adjustment step could have compromised the quality of the blanks, at least of the lower blanks, and could have damaged the sides of the stack. The Applicant also found that the engagement with the movement unit of large blanks, or stacks of blanks of considerable weight, could have been impaired in any event.

[0030] The Applicant envisioned increasing the distance along the longitudinal direction between the grasping elements of the movement unit in such a way as to increase the sizeof the portion of stack internal to the grasping elements and consequently reduce the size of the outer portion(s) of the stack. However, the Applicant verified that this option would have compromised the proper restraint of the stack and in particular that the internal portion of the stack tended to collapse under the weight of the stack itself, thus slipping on the grasping elements. The Applicant found that this defect was more pronounced in the case of blanks made of light, or flexible material, and / or as the number of blanks in each stack increased. Therefore, the Applicant verified that this would not have allowed for the correct engagement of smaller stacks of blanks and would not have eliminated the risk of unwanted displacements of the stack on the movement unit.

[0031] The Applicant also imagined picking up piles with a reduced number of blanks with the movement unit in order to reduce the overall weight of the stack picked up and thus stack deformation phenomena. However, the Applicant verified that this would result in slowing down the productivity of the packaging apparatus without, however, completely solving the problems encountered.

[0032] The Applicant therefore envisaged arranging the storage unit in the vicinity of the feeding unit or the processing unit so as to reduce the movement path of the blanks by the movement unit and thus the occurrence and / or extent of deformations of the blanks. However, the Applicant verified that such an intervention would have a considerable impact on the overall configuration and costs of a packaging apparatus. Furthermore, the Applicant verified that this would not always be feasible due to the dimensional and operational characteristics of the transformation unit.

[0033] The Applicant also found that these solutions would severely limit the production capacity of a packaging plant. Moreover, the Applicant verified that this approach would not have prevented some blanks from being bent or damaged, during picking and movement by the movement unit.

[0034] The Applicant also found that as the speed of handling the blanks increased, e.g. to increase the production capacity of the packaging machine, bending or tearing of the blanks occurred more frequently.

[0035] The Applicant therefore envisaged reducing the movement speed of the blanks. However, the Applicant verified that this would not only compromise the overall productivity of the packaging plant, but would also not solve the above-mentioned defects.

[0036] The Applicant therefore realised that in order to limit the possibility of damage to the blanks during picking up by the movement unit, it was necessary to rethink the unit for moving blanks.

[0037] The Applicant therefore realised that in order to achieve the aforementioned purpose while maintaining high production capacities, it was necessary to identify an operating mode that would allow for the permanent engagement of stacks of blanks even of different sizes, thicknesses, or characteristics.

[0038] The Applicant, in particular, realised that the possibility of generating damage or bending to the blanks was related to the engagement of the blanks with the movement unit and, therefore, that optimising the grasping elements would make it possible to avoid unwanted bending or damage to the blanks in the stack without thereby limiting the movement speed of the blanks.

[0039] The Applicant finally found that a method and unit for feeding blanks that involves engaging a stack of blanks with the grasping elements and with at least one grasping appendage made entirely with the grasping elements, surprisingly allows for the effective retention of blanks avoiding unwanted tearing of the blanks while maintaining high production speeds without the need for continuous operator action.

[0040] In other words, the Applicant found that the provision of a grasping appendage intended to engage the blanks in a different grasping portion with respect to the grasping elements allows for the effective engagement of stacks of blanks while at the same time avoiding unwanted displacements of the blanks, or unwanted bending of the blanks on the movement unit.

[0041] In a first aspect thereof, therefore, the present invention relates to a movement unit of a stack of blanks.

[0042] Preferably the movement unit comprises a support structure.

[0043] Preferably, the movement unit comprises a first grasping device and a second grasping device fixed to the support structure and intended to engage the blanks of the stack of blanks and mutually spaced along a longitudinal direction of said support structure so as to engage said blanks in a first longitudinal portion and in a second longitudinal portion spaced from said first longitudinal portion along said longitudinal direction.

[0044] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.

[0045] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.

[0046] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0047] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along the grasping direction arranged perpendicular to said longitudinal direction.

[0048] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.

[0049] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0050] Preferably, the first grasping device comprises at least one grasping appendage fixed to and integral with said first grasping element and spaced from said first grasping element along said longitudinal direction and configured to engage a third longitudinal portion of said stack of blanks spaced along said longitudinal direction from said first longitudinal portion and said second longitudinal portion.

[0051] Preferably said third longitudinal portion is oscillatable with respect to said second longitudinal portion and / or said first longitudinal portion.

[0052] In a second aspect thereof, the invention relates to a packaging apparatus for packing articles into boxes by folding a blank.

[0053] The apparatus preferably comprises a movement unit for moving a stack of blanks.

[0054] Preferably the movement unit comprises a support structure.

[0055] Preferably, the movement unit comprises a first grasping device and a second grasping device fixed to the support structure and intended to engage the blanks of the stack of blanks and mutually spaced along a longitudinal direction of said support structure so as to engage said blanks in a first longitudinal portion and in a second longitudinal portion spaced from said first portion along said longitudinal direction.

[0056] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.

[0057] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.

[0058] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0059] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along the grasping direction arranged perpendicular to said longitudinal direction.

[0060] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.

[0061] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0062] Preferably, the first grasping device comprises at least one grasping appendage fixed to and integral with said first grasping element and spaced from said first grasping element along said longitudinal direction and configured to engage a third longitudinal portion of said stack of blanks spaced along said longitudinal direction from said first portion and said second portion.

[0063] Preferably said third longitudinal portion is oscillatable with respect to said second longitudinal portion and / or said first longitudinal portion.

[0064] In a third aspect thereof, the invention relates to a method for moving a stack of blanks.

[0065] Preferably, this method comprises providing a movement unit having a support structure provided with a first grasping device and a second grasping device mutually spaced along a longitudinal direction of said support structure and configured to engagesaid blanks in a first longitudinal portion and a second longitudinal portion spaced along said longitudinal direction.

[0066] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.

[0067] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.

[0068] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0069] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along said grasping direction arranged perpendicular to said longitudinal direction.

[0070] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.

[0071] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0072] Preferably, the first grasping device comprises at least one grasping appendage fixed to and integral with said first grasping element and spaced from said first grasping element along said longitudinal direction and configured to engage a third longitudinal portion of said stack of blanks spaced along said longitudinal direction from said first portion and said second portion.

[0073] Preferably said third longitudinal portion is oscillatable with respect to said second longitudinal portion and / or said first longitudinal portion.

[0074] Preferably said method comprises moving said support structure towards said stack of blanks.

[0075] Preferably said method comprises moving at least one of said first and said second grasping elements along said grasping direction and at least one of said third and said fourth grasping elements along said grasping direction to bring said grasping elements closer to said stack of blanks.

[0076] Preferably said method comprises inserting said grasping teeth below said lower surface of said stack of blanks to support said stack of blanks, and abutting said third longitudinal portion with said at least one appendage to prevent an oscillation of said third longitudinal portion with respect to said first longitudinal portion and / or said second longitudinal portion.

[0077] In a fourth aspect thereof, the invention relates to a movement unit for moving a stack of blanks.

[0078] Preferably the movement unit comprises a support structure.

[0079] Preferably, the movement unit comprises a first grasping device and a second grasping device fixed to the support structure and intended to engage the blanks of the stack of blanks and mutually spaced along a longitudinal direction of said support structure so as to engage said blanks in a first longitudinal portion and in a second longitudinal portion spaced from said first portion along said longitudinal direction.

[0080] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.

[0081] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.

[0082] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0083] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along said grasping direction arranged perpendicular to said longitudinal direction.

[0084] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.

[0085] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0086] Preferably at least one of the third grasping element and the fourth grasping element is provided with an abutment element extending transversely with respect to said longitudinal direction and said grasping direction and intended to abut a lateral flank of said stack.

[0087] Preferably said abutment element is made of a yieldable material that yields to deform against said lateral flank of said stack when said second grasping device abuts said stack of blanks.

[0088] In a fifth aspect thereof, the invention relates to an apparatus having a movement unit for moving a stack of blanks.

[0089] Preferably the movement unit comprises a support structure.

[0090] Preferably, the movement unit comprises a first grasping device and a second grasping device fixed to the support structure and intended to engage the blanks of the stack of blanks and mutually spaced along a longitudinal direction of said support structure so as to engage said blanks in a first longitudinal portion and in a second longitudinal portion spaced from said first portion along said longitudinal direction.

[0091] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.

[0092] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.

[0093] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0094] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along said grasping direction arranged perpendicular to said longitudinal direction.

[0095] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.

[0096] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.

[0097] Preferably at least one of the third grasping element and the fourth grasping element is provided with an abutment element extending transversely with respect to said longitudinal direction and said grasping direction and intended to abut a lateral flank of said stack.

[0098] Preferably said abutment element is made of a yieldable material that yields to deform against said lateral flank of said stack when said second grasping device abuts said stack of blanks.

[0099] In a seventh aspect thereof, the invention relates to a method for moving a stack of blanks.[000100] Preferably, this method comprises providing a movement unit having a support structure provided with a first grasping device and a second grasping device mutually spaced along a longitudinal direction of said support structure and configured to engage said blanks in a first longitudinal portion and a second longitudinal portion spaced along said longitudinal direction.[000101] Preferably said first grasping device comprises a first grasping element and a second grasping element mutually facing and spaced along a grasping direction arranged perpendicular to said longitudinal direction.[000102] Preferably at least one of the first grasping element and the second grasping element is movable along the grasping direction to adjust the distance between the first and second grasping element along the grasping direction.[000103] Preferably, at least one of the first grasping element and the second grasping element is provided with a first grasping tooth extending along said grasping direction towards the other of said second grasping element or, respectively, said first grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.[000104] Preferably said second grasping device comprises a third grasping element and a fourth grasping element mutually facing and spaced along said grasping direction arranged perpendicular to said longitudinal direction.[000105] Preferably at least one of the third grasping element and the fourth grasping element is movable along the grasping direction to adjust the distance between the third and fourth grasping element along the grasping direction.[000106] Preferably, at least one of the third grasping element and the fourth grasping element is provided with a second grasping tooth extending along said grasping direction towards the other of said fourth grasping element or, respectively, said third grasping element and intended to engage a lower surface of said stack of blanks to support said stack of blanks.[000107] Preferably at least one of the third grasping element and the fourth grasping element is provided with an abutment element extending transversely with respect to said longitudinal direction and said grasping direction and intended to abut a lateral flank of said stack.[000108] Preferably said abutment element is made of a yieldable material that yields to deform against said lateral flank of said stack when said second grasping device abuts said stack of blanks.[000109] Preferably said method comprises moving said support structure towards said stack of blanks.[000110] Preferably said method comprises moving at least one of said first and said second grasping elements along said grasping direction and at least one of said third and said fourth grasping elements along said grasping direction to bring said grasping elements closer to said stack of blanks.[000111] Preferably, said method comprises inserting said grasping teeth below said lower surface of said stack of blanks to support said stack of blanks and abutting a lateral flank of said stack of blanks with said abutment element.[000112] Preferably said approach includes pushing said abutment element against said lateral flank so as to deform said abutment element against said lateral flank.[000113] In an eighth aspect of the invention, a pick-up head is provided for picking up and moving a group of articles, preferably a bundle of blanks.[000114] Preferably said head comprises at least a first pair of grasping elements mutually facing each other and a second pair of grasping elements mutually facing each other, thefirst and second pairs of grasping elements cooperating with each other to engage a lower surface of the group of articles.[000115] Preferably, said head comprises a splaying mechanism active between the grasping elements of the first and second pairs to move the grasping elements of the first and second pairs away or towards each other along a first horizontal direction. The horizontal direction is preferably the grasping direction.[000116] Preferably said head comprises a spacer mechanism active between the first and second pairs of grasping elements to adjust the distance between the grasping elements of the first pair and the grasping elements of the second pair along a second horizontal direction, transverse to the first horizontal direction.[000117] Preferably said head at least a first grasping element of said grasping elements comprises at least one abutment element configured to abut the group of articles to be picked in an abutment portion of the articles and to determine a predefined positioning of the articles with respect to the grasping head during picking and movement of the group of articles, said abutment element and said abutment portion being at least partially coupled to each other according to a shape coupling.[000118] In a seventh aspect of the invention, a pick-up head is provided for picking up and moving a group of articles, preferably a bundle of blanks.[000119] Preferably said head comprises at least a first pair of grasping elements mutually facing each other and a second pair of grasping elements mutually facing each other, the first and second pairs of grasping elements cooperating with each other to engage a lower surface of the group of articles.[000120] Preferably, said head comprises a splaying mechanism active between the grasping elements of the first and second pairs to move the grasping elements of the first and second pairs away or towards each other along a first horizontal direction. The horizontal direction is preferably the grasping direction.[000121] Preferably said head comprises a spacer mechanism active between the first and second pairs of grasping elements to adjust the distance between the grasping elements of the first pair and the grasping elements of the second pair along a second horizontal direction, transverse to the first horizontal direction.[000122] Preferably said head at least a first grasping element of said grasping elements comprises at least one abutment element configured to abut the group of articles to be picked in an abutment portion of the articles and to determine a predefined positioning of the articles with respect to the grasping head during picking and movement of the group ofarticles, said abutment element and said abutment portion being at least partially coupled to each other according to a shape coupling.[000123] Thanks to the invention, it is possible to engage and handle stacks of blanks with panels of various sizes without having to adjust the position of the elements every time the size of the blanks to be moved changes.[000124] Stacks of blanks made up of even a large number of blanks can be engaged and moved without risking unwanted bending of the panels of the blanks.[000125] The invention optimises the weight distribution of the stack of blanks on the movement unit by preventing unwanted displacements of the stack on the movement unit. This prevents the formation of high modulus torques with respect to the grasping elements, which could cause unwanted bending of the blanks with respect to the grasping elements. In addition, unwanted oscillations of portions of the stack of blanks are avoided.[000126] This prevents panels of the blanks that are not engaged by the retaining elements from oscillating relative to their intended folding line, deforming the blank. This advantage is achieved without the need to adjust the position of the grasping elements or the risk of large panels collapsing under the weight of the panels of the stack. It is not necessary to reduce the number of blanks of the stack in order to reduce the overall weight of the stack and to attempt to limit the occurrence of deformations of the blanks.[000127] Thanks to the invention, it is possible to engage and handle stacks of blanks with a considerable number of blanks without risking damage to the blanks themselves.[000128] In addition, the invention makes it possible to engage and move stacks of blanks with irregularly shaped panels. By engaging the stack of blanks with the grasping elements and the grasping appendage, blanks of various shapes and sizes can be securely engaged and retained without complicating the procedures for picking up blanks or unloading blanks from the movement unit.[000129] It is therefore possible to handle blanks correctly, avoiding unwanted displacement of the blanks, or bending of the blanks, without compromising the overall efficiency of the movement operations.[000130] Thanks to the invention, it is possible to retain the blanks of the stack to be moved more firmly.[000131] Providing a deformable abutment element improves the engagement of the movement unit with the stack of blanks and in particular with a portion of the lateral flank of the stack of blanks. When the movement unit is moved to engage the stack of blanks, the abutment element abuts a portion of the lateral flank and is deformed against thatportion of the lateral flank of the stack, adapting to the shape of the portion of the lateral flank of the stack. The abutment element adapts to the shape of the lateral flank of the stack by shape coupling to the portion of the lateral flank with which it comes into contact. The surface area of the lateral flank of the stack abutted by the abutment element is therefore increased. In addition, the adherence of the abutment element to the lateral flank of the stack is improved, even if the abutment element engages the stack in an area of discontinuity of the lateral flank. If, for example, there are corners or recesses in the lateral flank of the stack, the deformable abutment element can deform and adhere to the wall of the corner or recess, ensuring better engagement of the stack. It is therefore not necessary to adjust the longitudinal position of the first grasping device to ensure that the abutment element firmly engages the stack.[000132] In particular, the deformable abutment element can also be positioned at a bending line of the blanks where the lateral flank of the blanks can be irregular or discontinuous, ensuring firm engagement of the stack.[000133] Furthermore, it is not necessary to increase the size of the abutment element in order to increase the portion of the lateral flank surface area engaged by the abutment element.[000134] These advantages are obtained without the handling unit of the invention interfering with the operation of the movement unit or the loading / unloading of blanks onto or from the movement unit.[000135] Furthermore, thanks to the invention, adjustment operations on the movement unit are reduced, or even eliminated, and thus operator interventions, thus greatly simplifying the movement operations.[000136] It also severely limits, or eliminates, the possibility of a blank being torn or bent during pick-up by the movement unit or during transport on the movement unit.[000137] The invention also ensures high precision in the positioning of blanks in a processing station.[000138] The present invention, in at least one of the aforementioned aspects, may have at least one of the further preferred features listed below.[000139] In some preferred versions, said stack of blanks consists of a plurality of blanks placed on top of each other and positioned so that the faces of two adjacent blanks face each other and are in contact with each other. The stack preferably has two opposing faces corresponding to the faces of the blanks and a plurality of flanks with a height corresponding to the number of blanks in the stack. Preferably the stack has at least twoopposing lateral flanks along a transverse direction of the stack, a front flank and an opposing rear flank along a longitudinal direction of the stack.[000140] The width, or transverse extension, of the stack or a longitudinal portion of the stack is defined as the distance between the lateral sides of the stack at a given longitudinal position. The length, or longitudinal extension, of the stack is defined as the distance between the front and rear flanks of the stack at a given transverse portion. The width of the stack can vary along the longitudinal direction of the stack, and similarly, the length of the stack can vary along the transverse direction of the stack.[000141] The stack of blanks is placed in a blanks storage unit from which the blanks are picked up by the movement unit. The stack of blanks is placed on a support base of the storage unit with preferably horizontal orientation and defining a horizontal support plane for the stack. The stack is preferably positioned in such a way that the lower face of the bottom blank is supported on the support base, the upper face of the stack of blanks opposes the support base, and the height of the stack is defined as the distance between the upper face and the support base.[000142] The grasping elements engage the stack in grasping distinct portions so that an inner portion of the stack is defined as the portion of the stack interposed between the grasping elements and at least one outer portion of the stack corresponding to the portion of the stack arranged outside the grasping elements and extending outside the grasping elements along the longitudinal direction of the support structure.[000143] Preferably, each blank of said stack of blanks comprises a plurality of intended folding lines defining on the blank a plurality of panels, two adjacent panels of said plurality of panels being mutually connected by a respective intended folding line to be able to oscillate with respect to each other. Preferably at least one intended folding line of the plurality of folding lines is interposed between said third longitudinal portion and said first longitudinal portion and / or said second longitudinal portion.[000144] Preferably said third longitudinal portion is defined in a different panel of the blanks from the panel, or panels, on which said first longitudinal portion and / or said second longitudinal portion is defined.[000145] In some preferred embodiments, the movement unit comprises a movement member for moving said support structure between a grasping configuration in which the support structure is inserted into the storage unit in a position close to the support base and the grasping elements are close to the stack of blanks, and an engagement configuration in which the grasping elements are pushed into contact with the stack ofblanks and the first and second grasping devices engage and retain the blanks of the stack of blanks. In the engagement configuration, preferably said first engagement tooth engages a lower surface of said stack of blanks to support said stack of blanks. In the engagement configuration, preferably said second engagement tooth engages a lower surface of said stack of blanks to support said stack of blanks.[000146] In some preferred versions in said engagement configuration, said abutment element is in contact with a lateral flank of said stack. In some versions in said engagement configuration said abutment element is deformed against said lateral flank of said stack.[000147] Preferably said movement member is configured to move at least one of said first and said second grasping element and at least one of said third and said fourth grasping element along said grasping direction to move said support structure between said grasping configuration and said engagement configuration.[000148] Preferably, said third longitudinal portion is oscillatable about an axis of oscillation parallel to said first grasping tooth when said first grasping tooth engages a lower surface of said stack of blanks to support said stack of blanks.[000149] Preferably, said third longitudinal portion is oscillatable about an axis of oscillation parallel to said second grasping tooth when said second grasping tooth engages a lower surface of said stack of blanks to support said stack of blanks.[000150] Preferably said third longitudinal portion has a different transverse extension considered along said grasping direction from the transverse extension of said first longitudinal portion or the transverse extension of said second longitudinal portion.[000151] Preferably, the transverse extension of the third longitudinal portion is smaller than the transverse extension of the first longitudinal portion and / or the second longitudinal portion.[000152] In some versions, the first grasping element and the second grasping element are arranged on said support structure at the same longitudinal position so as to abut said stack of blanks at the same longitudinal position.[000153] In some versions, the first grasping element and the second grasping element are arranged longitudinally offset on said support structure so as to abut said first portion of said blanks in longitudinally offset positions.[000154] In some versions, said third grasping element and said fourth grasping element are arranged on said support structure at the same longitudinal position so as to abut said stack of blanks at the same longitudinal position.[000155] In some versions the third grasping element and the fourth grasping element are offset longitudinally on said support structure so as to abut said second portion in longitudinally offset positions.[000156] In some preferred versions said first grasping element comprises a first grasping tooth extending along said grasping direction towards the second grasping element and said second grasping element comprises a third grasping tooth extending along said grasping direction towards the first grasping element. In this way, the grasping teeth project towards each other and engage the stack of blanks.[000157] Preferably said first and said third grasping teeth are facing and arranged at the same longitudinal position of the support structure so as to abut said stack at the same longitudinal position.[000158] In some preferred versions said third grasping element comprises a second grasping tooth extending along said grasping direction towards the fourth grasping element and said fourth grasping element comprises a fourth grasping tooth extending along said grasping direction towards the third grasping element.[000159] Preferably said second and said fourth grasping teeth are facing and arranged at the same longitudinal position of the support structure so as to abut said stack at the same longitudinal position.[000160] Preferably, said first grasping device comprises a first grasping pair comprising in turn the first grasping element and the second grasping element which is opposed along said transverse direction and facing said first grasping element.[000161] The first and second pairs of grasping elements cooperate with each other to engage a lower surface of a group of articles. In other words, the grasping elements cooperate to support the group of articles underneath to allow them to be picked up.[000162] Preferably said first grasping tooth and said third grasping tooth extend along said grasping direction towards the opposing grasping element of the first grasping pair.[000163] Preferably said second grasping device comprises a second grasping pair comprising in turn the third grasping element and the fourth grasping element which is opposed along said transverse direction and facing said third grasping element.[000164] Preferably said second grasping tooth and said fourth grasping tooth extend along said grasping direction towards the opposing grasping element of the second grasping pair.[000165] Preferably said first and second grasping teeth are coplanar and define a grasping plane of the movement unit.[000166] Preferably said grasping plane is a horizontal plane.[000167] Preferably said grasping plane is parallel to the support plane of the base when said movement unit engages said stack of blanks.[000168] Preferably said first grasping device is configured so that said grasping appendage is spaced from said first grasping element along said grasping direction.[000169] Preferably said grasping appendage comprises an engagement tooth extending along said grasping direction and intended to engage a lower surface of said stack of blanks to support said stack of blanks.[000170] Preferably said engagement tooth has an extension considered along said transverse direction greater than the transverse extension of said first grasping tooth and / or said second grasping tooth. This makes it possible to stably engage said third longitudinal portion. It is also possible to effectively engage panels with limited extension in the transverse direction with the engagement tooth without having to bring the grasping elements of the first and / or second grasping device too close together. It is therefore possible to engage and handle stacks of blanks with irregularly shaped panels where, for example, an outer panel is smaller than the central panels.[000171] Preferably said engagement tooth is configured to project along said transverse direction more than said first grasping tooth and / or said second grasping tooth. This makes it possible to effectively engage panels with limited extension in the transverse direction with the engagement tooth.[000172] Preferably said engagement tooth has an extension considered along said grasping direction greater than half the transverse extension of the stack at the third longitudinal portion. In this way, the engagement tooth extends over half the width of the stack. It is therefore possible to effectively engage panels with a considerable width or even panels with a limited width and less than that of the first longitudinal portion and / or the second longitudinal portion with the engagement tooth.[000173] Preferably, said third portion is oscillatable about an axis of oscillation parallel to said engagement tooth when said engagement tooth engages a lower surface of said stack of blanks to support said stack of blanks.[000174] In some preferred versions, said grasping appendage comprises a retaining element arranged transversely to said engagement tooth and intended to retain a first lateral flank of said stack of blanks.[000175] Preferably said retaining element is arranged perpendicular to said engagement tooth.[000176] Preferably said retaining element is arranged so as to extend along a vertical direction perpendicular to said longitudinal direction and to said grasping direction.[000177] Preferably said retaining element and said engagement tooth are configured to define an “L”-shaped grasping appendage.[000178] Preferably said engagement tooth is provided at a free end of said retaining element, preferably opposite said support structure.[000179] Preferably said grasping appendage is positioned so that said first grasping element is interposed in the longitudinal direction between said third grasping element and said grasping appendage.[000180] Preferably said grasping appendage is positioned so that said first grasping tooth of said first grasping element is interposed in the longitudinal direction between said second grasping tooth of said third grasping element and the engagement tooth of said grasping appendage.[000181] In some versions, the engagement tooth is arranged coplanar with said first grasping tooth.[000182] In some versions, the engagement tooth is arranged coplanar with said second grasping tooth.[000183] In some versions, the engagement tooth, the first grasping tooth and the second grasping tooth are coplanar.[000184] In some versions, the movement unit comprises a second grasping appendage fixed to and integral with the second grasping element and spaced from said second grasping element along said longitudinal direction.[000185] Preferably the second appendage is spaced from said second grasping element along said grasping direction.[000186] Preferably, the second appendage is configured to engage a fourth longitudinal portion of said stack of blanks spaced along said longitudinal direction from said first longitudinal portion and said second longitudinal portion.[000187] In some versions, the second appendage is positioned so that said fourth longitudinal portion of said stack of blanks is spaced along said longitudinal direction from said third longitudinal portion.[000188] Preferably said fourth longitudinal portion is oscillatable with respect to said second longitudinal portion and said first longitudinal portion.[000189] Preferably said fourth longitudinal portion is oscillatable about a second axis of oscillation parallel to the first axis of oscillation.[000190] In one version, said third longitudinal portion and said fourth longitudinal portion are provided on different panels of said blanks, said fourth longitudinal portion being able to oscillate with respect to said third longitudinal portion.[000191] In some versions, said third longitudinal portion and said fourth longitudinal portion are provided on the same panel of said blank in mutually different longitudinal positions.[000192] In some versions, said third longitudinal portion is oscillatable about a first axis of oscillation and said fourth longitudinal portion is oscillatable about a second axis of oscillation parallel to the first axis of oscillation.[000193] Preferably, said second grasping appendage comprises a second engagement tooth extending along said grasping direction and intended to engage a lower surface of said stack of blanks to support said stack of blanks.[000194] Preferably said second grasping appendage comprises a second retaining element arranged transversely to said second engagement tooth and intended to retain a second lateral flank of said stack of blanks, said second lateral flank being provided on the opposite side to said lateral flank with respect to said transverse direction.[000195] Preferably said second grasping appendage comprises a second retaining element arranged perpendicularly to said second engagement tooth.[000196] Preferably said second appendage is positioned so that said second grasping tooth is interposed in the longitudinal direction between said fourth grasping tooth and the second engagement tooth.[000197] Preferably said second grasping appendage and said first grasping appendage are configured so that the first engagement tooth and the second engagement tooth are offset along said longitudinal axis so as to engage said blanks in longitudinally spaced portions. In other words, the first engagement tooth and the second engagement tooth are arranged so that their respective extensions run along straight lines that neither intersect nor coincide. This makes it possible to use engagement teeth with a considerable extension without the risk of the first engagement tooth and the second engagement tooth interfering with each other when using the movement unit. This makes it possible to optimise the grasp of the stack of blanks. In particular, it is possible to use engagement teeth having a greater extension than the corresponding grasping teeth and / or extending for a greater extension along the grasping direction than the corresponding grasping teeth.[000198] This also ensures that when the format of the blanks to be picked does not require the supporting appendages to be operationally active, i.e. when the appendages do not support a portion of the blank, they do not interfere with each other.[000199] In some versions, said second grasping appendage and said first appendage are configured so that the first engagement tooth and the second engagement tooth engage separate panels of said blanks.[000200] Preferably said second appendage is positioned so that said third grasping tooth is interposed in the longitudinal direction between said fourth grasping tooth and said second engagement tooth.[000201] In one version, said second appendage is positioned so that the second engagement tooth is arranged coplanar with the third grasping tooth.[000202] In one version said second appendage is positioned so that said second engagement tooth is arranged coplanar with the first engagement tooth.[000203] In some versions, at least one of the first grasping element, the second grasping element, the third grasping element and the fourth grasping element is provided with an abutment element extending transversely with respect to said longitudinal direction and said grasping direction and intended to abut a lateral flank of said stack.[000204] In some versions, said abutment element is interposed between said support structure and the grasping tooth of the respective grasping element and is arranged to abut a lateral flank of said stack of blanks.[000205] In some versions, each of said first, second, third and fourth grasping elements comprises a respective abutment element interposed between said support structure and the grasping tooth of the respective grasping element and arranged to abut a lateral flank of said stack of blanks.[000206] In some versions, the third and fourth grasping elements comprise a respective abutment element interposed between said support structure and the grasping tooth of the respective grasping element and arranged to abut a lateral flank of said stack of blanks.[000207] Preferably, said abutment element extends transversely to the grasping tooth of the respective grasping element.[000208] Preferably said abutment element extends substantially perpendicular to the grasping tooth of the respective grasping element so as to define an “L”-shaped grasping element.[000209] In some versions, said abutment element is made of a yieldable material that yields to deform against said lateral flank of said stack when said grasping element abuts said stack of blanks.[000210] In some versions, at least one of said first, second, third or fourth abutment element is made of a yieldable material that yields to deform when abutting against said lateral flank of said stack of blanks.[000211] In some versions, said third and said fourth abutment elements are made of a yieldable material that yields to deform when abutting against said lateral flank of said stack of blanks.[000212] Preferably, said abutment element has a convex curved profile towards said stack of blanks, so as to improve the abutment between said grasping element and said stack of blanks.[000213] The abutment element is intended to contact an abutment portion defined on the lateral flank of the stack. Preferably, the abutment element and the abutment portion of the lateral flank from the stack of blanks can be at least partially coupled with each other according to a shape coupling.[000214] Preferably, the abutment element and the abutment portion have respective shapes configured to promote at least partial mutual coupling. It should be noted that this shape coupling occurs following the movement of the grasping elements towards one another, and thus in closure towards the group of articles.[000215] Preferably said abutment element comprises a tubular body with a convex curved surface towards said stack of blanks.[000216] In some versions, said abutment element comprises a support body extending between said support structure and the corresponding grasping tooth, and a damping element coupled to said support body and facing said stack of blanks, said damping element being intended to abut a lateral flank of said stack of blanks. Preferably said damping element is made of a yieldable material that yields to deform upon abutment with said lateral flank of said stack of blanks.[000217] Preferably said damping element has a convex curved profile towards said stack of blanks, so as to improve the abutment between said grasping element and said stack of blanks. The provision of damping elements with a convex curved profile towards the stack of blanks makes it possible to improve the abutment between the second grasping device and the stack of blanks. The provision of damping elements made of yieldable material improves the engagement and retention of the blanks. In use, the damping elements aredeformed against the flanks of the stack of blanks, holding them firmly in place. Moreover, such a conformation allows for the effective engagement of even irregularly shaped blanks. The provision of a damping element with a convex profile makes it possible to engage the stack of blanks in regions of discontinuity of the edge of the blanks, which can be foreseen, for example, at an intended folding line. In this region, cavities or slots of various shapes can be provided where the damping element allows for better engagement. It is therefore possible to effectively engage the blanks at areas of discontinuity where unwanted oscillations could be generated.[000218] Preferably said damping element comprises a tubular body with a convex curved surface towards said stack of blanks and adapted to be deformed in engagement with said stack of blanks.[000219] Preferably said tubular body is internally hollow.[000220] Preferably said support body comprises a rod made of rigid material, preferably metal.[000221] Preferably said abutment element comprises a deformable body fixed to said rod intended to abut said stack of blanks and made of a material yielding to deform during engagement with the stack of blanks to improve the engagement and retention of said stack.[000222] Preferably said first grasping element comprises a first abutment element interposed between said support structure and said first grasping tooth and arranged to abut a lateral flank of said stack of blanks. Preferably said first abutment element extends transversely, preferably perpendicularly, to said first grasping tooth.[000223] Preferably said first grasping tooth is fixed to one end of said first abutment element opposite said support structure and extends perpendicularly to said first retaining element so as to define an “L”-shaped grasping element.[000224] Preferably said second grasping element comprises a second abutment element interposed between said support structure and said third grasping tooth and arranged to abut a second lateral flank of said stack of blanks opposed along said grasping direction to said lateral flank. Preferably said second abutment element extends transversely, preferably perpendicularly, to said third grasping tooth.[000225] Preferably said third grasping tooth is fixed to one end of said second abutment element opposite said support structure and extends perpendicularly to said second retaining element so as to define an “L”-shaped grasping element.[000226] Preferably said third grasping element comprises a third abutment element interposed between said support structure and said second grasping tooth, and arranged to abut a lateral flank of said stack of blanks, said third abutment element extending preferably transversely, preferably perpendicularly, to said second grasping tooth.[000227] Preferably said second grasping tooth is fixed to one end of said third abutment element opposed to said support structure and extends perpendicularly to said third abutment element so as to define a third “L”-shaped grasping element.[000228] Preferably said fourth grasping element comprises a fourth abutment element interposed between said support structure and said fourth grasping tooth, and arranged to abut a second lateral flank of said stack of blanks opposed along said grasping direction to said lateral flank, said fourth abutment element extending transversely preferably perpendicularly to said fourth grasping tooth.[000229] Preferably said fourth grasping element is fixed to one end of said fourth abutment element opposite said support structure and extends perpendicularly to said fourth abutment element so as to define a fourth “L”-shaped grasping element.[000230] In some versions said first appendage is positioned so that said first abutment element is interposed in the longitudinal direction between said retaining element and said third abutment element.[000231] Preferably said first retaining element is spaced in the longitudinal direction and in the transverse direction from said first and / or said third abutment element.[000232] In some versions said second appendage is positioned so that said second abutment element is interposed in the longitudinal direction between said second retaining element and said fourth abutment element.[000233] Preferably said second retaining element is spaced in the longitudinal direction and in the transverse direction from said second and / or said fourth abutment element.[000234] In some versions said movement unit comprises a connecting element for fixing said appendage to said first grasping element, said connecting element extending between said first grasping element and said grasping appendage parallel to said grasping plane and spaced from said grasping plane.[000235] Preferably said connecting element has a profile adapted to follow the profile of a portion of said lateral flank of said stack of blanks interposed between said first grasping element and said grasping appendage.[000236] Preferably said connecting element extends between said first retaining element and said first abutment element and is inclined with respect to said transverse direction andsaid longitudinal direction. The retaining element is, therefore, spaced out from said abutment element in the transverse direction and in the longitudinal direction.[000237] In some versions said movement unit comprises a second connecting element for fixing said second appendage to said second grasping element, said second connecting element extending between said second grasping element and said second appendage parallel to said grasping plane and spaced from said grasping plane.[000238] Preferably said second connecting element has a profile adapted to follow the profile of a portion of said second lateral flank of said stack of blanks interposed between said second grasping element and said second appendage.[000239] Preferably said second connecting element extends between said second retaining element and said second abutment element and is inclined with respect to said transverse direction and said longitudinal direction. The second retaining element is, therefore, spaced out from said second abutment element in the transverse direction and in the longitudinal direction.[000240] In some versions, said movement unit comprises a splaying device for moving at least one of the first grasping element and the second grasping element along the grasping direction to adjust the transverse distance between the first grasping element and the second grasping element.[000241] Preferably, said splaying device comprises a worm gear which can be driven to move the first grasping element and / or the second grasping element along the grasping direction.[000242] Preferably said splaying device comprises a worm gear to which the first grasping element and the second grasping element are operatively connected and which can be driven to simultaneously move the first grasping element and the second grasping element along the grasping direction.[000243] In some versions, the movement unit comprises a second splaying device to move at least one of the third grasping element and the fourth grasping element along the grasping direction to adjust the transverse distance between the third grasping element and the fourth grasping element.[000244] Preferably, said splaying device comprises a worm gear which can be driven to move the third grasping element and / or the fourth grasping element along the grasping direction.[000245] Preferably said second splaying device comprises an endless screw to which the third grasping element and the fourth grasping element are operatively connected andwhich can be operated to simultaneously move the third grasping element and the fourth grasping element along the grasping direction.[000246] In some versions, the movement unit comprises a single splaying mechanism active between the grasping elements of the first and second pair to move the grasping elements of the first and second pair away or towards each other along a first horizontal direction, i.e. along the grasping direction.[000247] Preferably, the splaying device allows the grasping elements of the first and second pair to be opened and closed. Advantageously, this feature makes it possible to engage groups of articles by moving the grasping elements in a mutual approach towards the groups of articles.[000248] Advantageously, this feature makes it possible to release the engaged groups of articles from the grasping elements by moving the grasping elements in the open configuration away from the groups of articles.[000249] In some preferred embodiments, the movement unit further comprises an adjustable mechanism which can be driven to move at least one of said first grasping device and said second grasping device along said longitudinal direction to adjust the longitudinal distance between said first grasping device and said second grasping device. [000250] In some versions, the pick-up head comprises a spacer mechanism active between the first and second pairs of grasping elements to adjust the distance between the grasping elements of the first pair and the grasping elements of the second pair along a second horizontal direction, i.e. along the longitudinal direction. To clarify, the spacer mechanism is configured to move the first and second pairs of grasping elements away from each other or towards each other.[000251] Preferably, the spacer mechanism is configured to move one of the first and second pairs of grasping elements towards or away from each other.[000252] Advantageously, by means of the spacer mechanism, the distance between the pairs of graspper elements can be adjusted according to the size of the articles to be picked.[000253] In particular, when picking up bundles of blanks, it is possible to adjust the distance between pairs of grasping elements according to the size of the blanks of the bundles to be picked up.[000254] In some preferred versions, a specific portion of the articles can be abutted by the abutment element, which makes it possible to determine the position of the group of articles in relation to the pick-up head.[000255] To clarify, in use, the position of the groups of articles within the generic store from which they are picked is known, and the characteristics of the article to be picked, e.g. its size and shape, are known, so that a specific fixed portion of the articles to be picked can be abutted by the abutment element of the pick-up head, which makes it possible to determine precisely how the groups of articles are arranged in relation to the pick-up head that picked them.[000256] Advantageously, by determining a predefined positioning of the groups of articles in relation to the pick-up head during picking and movement ensures accuracy in the release position of the picked groups of articles.[000257] According to one aspect, the abutment element of the pick-up head and the abutment portion of the articles of the group of articles may comprise a male portion and a female portion, respectively, or vice versa, a female portion and a male portion, respectively.[000258] These male and female portions determine the shape coupling, at least partially, between the abutment element and the abutment portion.[000259] The movement unit preferably comprises movement means for moving the grasping elements. Such movement means are known in the industry and may include, for example, a system of guides and carriages for moving the grasping elements.[000260] This movement of the grasping elements by the system of guides and carriages can be aided by lubricants such as oil or grease.[000261] Preferably, the pick-up head comprises a plurality of channels arranged below each guide of said system of guides and carriages. Such channels are, for example, trays or gutters. Advantageously, the channels allow for the collection of lubricants such as grease or oil, which are used to facilitate the movement of the carriages on the respective guides, avoiding contamination or soiling of the picked articles.[000262] Preferably, the unit is configured to move groups of articles picked by the pickup head, for example, from a store to an article processing station.[000263] The unit includes a control unit configured to control the splaying mechanism and the spacer mechanism.[000264] To clarify, the control unit controls the movement of the grasping elements along the first horizontal direction and along the second horizontal direction.[000265] The control unit is then configured to control the movement of the grasping elements of each pair away from or towards each other, and to control the adjustment of the distance between pairs of grasping elements.[000266] The control unit is configured to control the movement of the pick-up head along the first horizontal direction, the second horizontal direction, the vertical direction and in rotation about an axis parallel to the vertical direction.[000267] In other words, the control unit is configured to control the movement of the pickup head relative to the machine's base structure along the first horizontal direction, the second horizontal direction, the vertical direction, and in rotation relative to an axis of rotation parallel to the vertical direction.[000268] Advantageously, the control unit allows the pick-up head to be moved to shift articles, picked by the pick-up head itself, for example, from a store to an article processing station.[000269] The method involves moving the first and second pair of grasping elements of the pick-up head away from or towards each other along the first horizontal direction.[000270] Advantageously, moving the grasping elements of the first and second pairs of the pick-up head away from or towards each other along the first horizontal direction makes it possible to engage the groups of articles by moving the grasping elements towards the groups of articles in the closed configuration.[000271] The method comprises moving the pick-up head along the first horizontal direction, the second horizontal direction, the vertical direction and in rotation about the axis of rotation.[000272] The method comprises coupling, at least partially, the abutment element and the abutment portion according to a shape coupling to determine a predefined positioning of the articles in relation to the pick-up head during pick-up and movement of the group of articles.[000273] Advantageously, abutting a specific portion of the articles via the abutment element allows the position of the group of articles relative to the pick-up head to be determined.[000274] Advantageously, determining a predefined positioning of the group of articles relative to the pick-up head during picking and movement of the articles ensures accuracy in the release position of the picked group of articles.[000275] In some versions, each grasping element further comprises a bracket fixed to the abutment element so that the latter is interposed between the bracket and the grasping tooth. Preferably, the bracket is positioned in such a way as to define a “C”-shaped grasping component with concavity facing towards the stack of blanks in use. This improves the grasp of the stack of blanks.[000276] In some versions, the bracket is intended to abut an upper surface of the stack of blanks. In this way, the stacks of blanks are inserted into the grasping elements, the lower surface of the stack being abutted and supported by the grasping tooth, the upper surface being abutted by the bracket and the lateral flank being abutted by the abutment element.[000277] In some versions, the grasping elements of one of the pairs are “C”-shaped with a greater depth concavity than the grasping elements of the other pair in order to engage with a wider portion of said blanks.[000278] The blanks may have a shape with portions of different widths and, therefore, advantageously, a greater depth concavity of the grasping elements of one pair of the pickup head than the grasping elements of the other pair allows the articles to be correctly engaged even when they have portions of different widths.[000279] The features and the advantages of the present solution will become clearer from the detailed description of an embodiment thereof, illustrated by way of non-limiting example, with reference to the appended drawings in which:[000280] Figure 1 is a schematic perspective view of an embodiment of a storage unit for blanks equipped with a unit for moving blanks in accordance with the present solution;[000281] Figure 2 is a perspective view of the unit for moving blanks in Figure 1 with some details removed for clarity;[000282] Figure 3 is a perspective view of the unit for moving blanks in accordance with the present solution in a first operational configuration;[000283] Figure 4 is a front view of the unit for moving blanks in Figure 3;[000284] Figure 5 is a bottom view of the unit for moving blanks in Figure 3;[000285] Figure 6 is a perspective view of the unit for moving blanks in accordance with the present solution in a second operational configuration;[000286] Figure 7 is a front view of the unit for moving blanks in Figure 5;[000287] Figure 8 is a perspective view of the unit for moving blanks in Figure 5 with some details removed for clarity;[000288] Figure 9 is a bottom view of the unit for moving blanks in Figure 6;[000289] Figure 10 is a partial schematic view of a picking and movement apparatus comprising the movement unit in Figure 1 .[000290] In the enclosed Figures, a movement unit for moving stacks of blanks 100 manufactured in accordance with the present solution is collectively referred to as 1 . The movement unit 1 is preferably used in a boxing apparatus or, in general, in formingapparatus where a box is to be formed by folding a blank. In a preferred version, the feeding unit is to be used in a wrap-around packaging apparatus, whereby the packaging is made by folding a blank around an article to be packaged to form a box containing the article. The movement unit 1 is intended to pick a stack of blanks 100 from a unit for storing blanks200 and move it to a unit for feeding blanks (not shown in the figures) or to a processing unit where the blanks can be folded to form boxes.[000291] The storage unit 200, shown schematically in Figure 1 , comprises a support base201 adapted to constitute the support base for the stack of blanks 100 and to support one or more stacks of blanks 100. The support base 201 has a planar shape. In a Cartesian reference with three orthogonal axes, the support base 201 extends along a horizontal plane XY defined by a longitudinal axis X and a transverse axis Y, the vertical axis Z being perpendicular to the support base 201. The storage unit 200 is also provided with positioning rods 203 fixed to the support base 201 and extending from the support base 201 in a substantially vertical direction and intended to guide the positioning of the stacks of blanks 100 on the support base 201 .[000292] Each stack of blanks 100 consists of a plurality of blanks 101 , the number of blanks 101 in each stack of blanks 100 depending on the characteristics and dimensions of the blanks 101. The blanks 101 are placed in the stack 100 adjacent to each other so that the faces S of two adjacent blanks face each other and are in contact with each other. [000293] Each stack of blanks 100 therefore has a plan form having the shape and size of the face S of the blanks and is delimited by a lower face S’ intended to rest on the support base 201 , an opposing upper face S”, a plurality of flanks whose outline depends on the outline of the edge of the blanks 101 forming the stack and a height H1 depending on the number and thickness of the blanks forming the stack of blanks 100. The stack of blanks 100 has a front flank 100A, an opposing rear flank 100B and two opposing lateral flanks 100C, 100D. The distance between the two lateral flanks 100C, 100D will be referred to hereafter as the width, or transverse extension of the stack of blanks 100, the distance between the front flank 100A and the rear flank 100B of the stack of blanks 100 will be referred to hereafter as the length, or longitudinal extension of the stack of blanks.[000294] Each of the blanks 101 , best seen in Figures 5 and 9, is made of cardboard and has two substantially planar opposing faces S extending along a longitudinal direction X and a transverse direction Y substantially larger than the thickness dimensions of the blank 101. Each blank 101 usually has a thickness comprised between 0.4 mm and 0.8 mm, in this case about 0.5 mm, and is suitably shaped to form a box when properly folded. Forthis purpose, a plurality of folding lines 110 is obtained on the blank 101 that divide the blank 101 into a plurality of panels intended to form, alone or in combination with each other, the different faces of the box. The folding lines 110 are preferably creases and each pair of adjacent panels is oscillatable about a respective folding line 110 that separates them. The number and shape of the blanks depend on the shape and size of the box to be formed.[000295] In particular, in the version shown, the folding lines 110 are positioned so as to define in the blank 101 a central panel 102 of quadrangular shape to whose opposing side edges 102A-102B two side panels 103-103’ are hinged, and to whose opposing front edges 102C-102D an intermediate panel 104 and a rear panel 105 are hinged. The side panels 103, 103’ have the same longitudinal extension as the central panel 102. Adjacent to each side panel 103, 103’ is a respective folding flap 108, 108’. The blank further comprises a front panel 106 adjacent to the intermediate panel 104 and positioned so that in the longitudinal direction the intermediate panel 104 is interposed between the central panel 102 and the front panel 106.[000296] Thus, considering the longitudinal direction X of the blank 101 , the following panels are in succession in the blank 101 : the rear panel 105; the central panel 102 and side panels 103, 103’; the intermediate panel 104; the front panel 106. A respective intended folding line 110 is provided between two adjacent panels so that they can oscillate relative to each other. The axes of oscillation between the rear panel 105 and the central panel 102, between the central panel 102 and the intermediate panel 104 and between the intermediate panel 104 and the front panel 106 are parallel to each other.[000297] The blank 101 has variable extension along the longitudinal direction, the intermediate panel 104 and the front panel 106 have the same transverse extension. A first transverse extension M1 identified as the distance between the opposing side edges 106A- 106B of the end panel 106 or between the opposing side edges 104A-104B of the intermediate panel 104, a second transverse extension M2 regarded as the distance between the opposing side edges 103A-103B of the side panels 103-103’, a third transverse extension M3 regarded as the distance between the opposing side edges 105A- 105B of the rear panel 105. The front, rear, and side edges of the blanks may be defined by a continuous or broken line. In particular, a “V”-shaped recess 107 is provided at the folding line between the intermediate panel 104 and the end panel 106. The second transverse extension M2 is greater than the first and third transverse extension M1 , M3.The third transverse extension M3 is shorter than the second transverse extension M2 and than the first transverse extension M1 .[000298] The stack of blanks 100 is placed on the support base 201 in such a way that the lower face S’ rests on the support base 201 and is therefore arranged on a horizontal plane XY. It is further considered for simplicity that the stack of blanks 100 is positioned in the storage unit 200 so that the longitudinal axis of the blanks 101 coincides with the longitudinal axis X of the support base 201 and similarly the transverse axis of the blanks 101 coincides with the transverse axis Y of the support base 201 .[000299] The movement unit 1 comprises a pick-up head 6, shown in greater detail in Figures 2, 3, 7, 8 which can be driven to pick up successive stacks of blanks 100 from the storage unit 200 and move them to a processing unit, for example a blank feeding unit, not shown in the Figures.[000300] The pick-up head 6 comprises a support structure 2 which is fixed, by means of a support arm 7 A, to a movement member, not shown in the Figures, intended to drive the pick-up head 6, as further explained below. The support structure 2 comprises a support bar 7B to which a first grasping device 10 and a second grasping device 20 are fixed, intended to engage the blanks 101 of the stack of blanks 100 and mutually spaced along the longitudinal direction X. When the movement unit 1 is inserted into the storage unit 200 to engage and pick up a stack of blanks 100, as further clarified below, the support structure 2 is positioned so that its longitudinal axis X is parallel to and coincident with the longitudinal axis X of the support base 201 and the blanks 101 . Therefore, in the following, these axes will all be referred to as longitudinal axes and identified with corresponding references. Similarly, the transverse axis of the support structure 2 is parallel and coincident with the transverse axis of the blanks and the support base 201 , therefore, in the following these axes will both be referred to as transverse axes and identified with corresponding references.[000301] The support structure 2 comprises a support bar 7B extending along a longitudinal X axis of the support structure. The movement unit 1 comprises a first grasping device 10 and a second grasping device 20 fixed to the support bar 7B of the support structure 2 and intended to engage the blanks 101 of the stack of blanks 100 to move them. The first grasping device 10 and the second grasping device 20 are fixed in longitudinally spaced positions to the support bar 7B so that the first grasping device 10 engages the blanks 101 in a first longitudinal portion PA and the second grasping device 20 engagesthe blanks 101 in a second longitudinal portion PB spaced from the first longitudinal portion PA along the longitudinal direction X, as further clarified below.[000302] The first grasping device 10 and the second grasping device 20 are structurally similar, therefore, only one will be described in detail, and corresponding numerical references will be used for the corresponding parts.[000303] The first grasping device 10 comprises a first grasping element 11 and a second grasping element 15 mutually facing and spaced along a grasping direction Y arranged perpendicularly with respect to the longitudinal direction X so as to engage respectively the two opposing lateral flanks of the stack of blanks 100.[000304] The first grasping element 11 and the second grasping element 15 define a first 10A grasping pair of the first grasping device 10.[000305] The first grasping element 11 comprises a first grasping tooth 12 extending along the grasping direction Y towards the second grasping element and intended to engage a lower surface S of the stack of blanks 100 to support the stack of blanks 100. In addition, the first grasping element 11 comprises a first abutment element 13 interposed between the support structure 2 and the first grasping tooth 12 and arranged to abut a lateral flank 100C of the stack of blanks 100.[000306] The first abutment element 13 extends perpendicularly to the first grasping tooth 12, the first grasping tooth 12 being fixed to an end of the first abutment element 13 opposing the support structure 2, so as to form a first grasping element 11 configured in an “L” shape.[000307] The first abutment element 13 comprises a support body extending between the support structure 2 and the first grasping tooth 12. In a version not shown, the support body has a convex curved section towards the stack of blanks 100.[000308] Similarly, the second grasping element 15 comprises a third grasping tooth 16 extending along the grasping direction Y towards the first grasping element 11 and intended to engage a lower surface S of the stack of blanks 100 to support the stack of blanks 100. The third grasping tooth 16 is coplanar with the first grasping tooth 11 , and both lie on a grasping plane XY of the movement unit 1 . The grasping plane XY is a horizontal plane.[000309] Preferably said grasping plane is parallel to the support plane of the support base 201 when said movement unit engages said stack of blanks. The second grasping element 15 further comprises a second abutment element 17 interposed between the support structure 2 and the third grasping element 16 and arranged to abut a second lateral flank 100D of the stack of blanks 100. The second lateral flank 100D of the stack of blanks 100is opposed along the grasping direction Y to the first lateral flank 100C. In this way, the first abutment element 13 and the second abutment element 17 engage and retain opposing sides of the stack of blanks 100.[000310] The second abutment element 17 extends perpendicularly to the third grasping tooth 16. The third grasping tooth 16 is fixed to one end of the second abutment element 17 opposing the support structure 2 so as to create a second grasper element 15 configured in an “L” shape.[000311] The second abutment element 17 comprises a support body extending between the support structure 2 and the third grasping tooth 16.[000312] The first and second abutment elements 13, 17 extend along a vertical axis Z perpendicular to the grasping plane XY.[000313] In the version shown, the support structure 2 further comprises a bracket 47 fixed to the end of the first abutment element 13 opposing the first grasping tooth 12, so that the abutment element 13 is interposed between the bracket 47 and the first grasping tooth 12. The bracket 47 and the first grasping tooth are essentially parallel to each other. This defines a “C”-shaped grasping component. The grasping component has a concavity facing the stack of blanks to improve the retention of the blanks.[000314] Similarly, there is also a second bracket 48 fixed to the end of the second abutment element 17 opposing the third grasping tooth 16, so that the second abutment element 17 is interposed between the second bracket 48 and the third grasping tooth 16. The second bracket 48 and the third grasping tooth are essentially parallel to each other. This defines a second “C”-shaped grasping component.[000315] The first grasping element 11 and the second grasping element 15 are placed at the same longitudinal position so as to meet said stack of blanks 100 at the same longitudinal position PA. The first grasping tooth 12 and the third grasping tooth 16 are facing and arranged in the same longitudinal position.[000316] Similarly, the second grasping device 20 comprises a third grasping element 21 and a fourth grasping element 25 mutually facing and spaced along the grasping direction Y so as to engage opposing lateral flanks 100C, 100D of the stack of blanks 100.[000317] The third grasping element 21 comprises a second grasping tooth 22 extending along the grasping direction Y towards the fourth grasping element 25 and intended to engage a lower surface S of the stack of blanks 100 to support the stack of blanks 100. In addition, the third grasping element 21 comprises a third abutment element 23 interposedbetween the support structure 2 and the third grasping element 22 and arranged to abut a lateral flank 100C of the stack of blanks 100.[000318] The third abutment element 23 extends perpendicularly to the second grasping tooth 22 which is fixed to one end of the third abutment element 23 so as to create a third grasping element 21 configured in an “L” shape. The third abutment element 23 extends along a vertical axis Z perpendicular to the grasping plane XY.[000319] The third abutment element 23, best seen in Figures 3, 5, 8 and 9, comprises a support body 23A extending between the support structure 2 and the third grasping tooth 22 and a damping element 23B coupled to the support body 23A and facing in use towards the stack of blanks 100 so as to abut a lateral flank 100C of the stack of blanks 100. The damping element 23B is made of a yielding material to deform when abutting against the side of the stack of blanks to improve engagement with the stack of blanks. The damping element 23B has a convex curved profile towards the stack of blanks 100, so as to improve the abutment between the third grasping element 21 and the stack of blanks 100. In some versions not shown, the third abutment element is made entirely of yielding material.[000320] Similarly, the fourth grasping element 25 comprises a fourth grasping tooth 26 extending along the grasping direction Y towards the third grasping element 21 and intended to engage a lower surface S of the stack of blanks 100 to support the stack of blanks 100. The fourth grasping element 25 further comprises a fourth abutment element 27 interposed between the support structure 2 and the fourth grasping tooth 26 and arranged to abut a second lateral flank 100D of the stack of blanks 100 opposed along the grasping direction Y to the first lateral flank 100C. In this way, the third 23 and fourth abutment element 27 engage and retain opposing sides of the stack of blanks 100.[000321] The fourth abutment element 27 extends perpendicularly to the fourth grasping tooth 26 which is fixed to one end of the fourth abutment element 27 so as to create a fourth grasping element 25 configured in an “L” shape. The fourth abutment element 27 extends along a vertical Z axis perpendicular to the grasping plane XY.[000322] The fourth abutment element 27 comprises a support body 27A extending between the support structure 2 and the fourth grasping tooth 26 and a further damping element 27B coupled to the support body 27A and facing in use towards the stack of blanks 100 so as to abut a second lateral flank 100D of the stack of blanks 100. The additional damping element 27B is made of a yielding material to deform upon contact with the second lateral flank 100D of the stack of blanks 100 and has a convex curved profile towards the stack of blanks 100 in order to improve the abutment between the fourth grasping elementand the stack of blanks. In some versions not shown, the fourth abutment element is made entirely of yielding material.[000323] The grasping teeth 12, 16, 22, 26 are arranged coplanar and jointly define the grasping plane XY of the movement unit.[000324] The first grasping device 10 further comprises a first grasping appendage 30 fixed to and integral with the first grasping element 11 . The first grasping appendage 30 is spaced from the first grasping element 11 along the longitudinal direction X in such a way as to engage the stack of blanks in a third longitudinal portion PC spaced along the longitudinal direction X from the first longitudinal portion PA and the second longitudinal portion PB.[000325] In the embodiment shown, the second longitudinal portion PB is defined at the recess 107 provided on the folding line 110 between the intermediate panel 104 and the end panel 106, the first longitudinal portion PA is defined at the central panel 102 and the side panels 103, 103’ and the third longitudinal portion PC is defined at the rear panel 105, however in other embodiments not shown, the movement unit 1 may engage the stack of blanks in distinct portions thereof.[000326] The grasping appendage 30 comprises a first engagement tooth 31 extending along the grasping direction Y and intended to engage a lower surface S of the stack of blanks 100 to support the stack of blanks 100. The grasping appendage 30 further comprises a retaining element 32 arranged transversely to the engagement tooth 31 , preferably perpendicular to the engagement tooth 31 and intended to retain the first lateral flank 100C of the stack of blanks 100. The retaining element 32 extends along a vertical axis Z perpendicular to the longitudinal direction X and the grasping direction Y.[000327] The retaining member 32 and the engagement tooth 31 are configured to define an “L”-shaped grasping appendage 30, wherein the engagement tooth 31 is provided at an end of the retaining member 32 opposing the support structure 6.[000328] The grasping appendage 30 is positioned so that the first grasping element 11 is interposed in the longitudinal direction X between the third grasping element 21 and the grasping appendage 30. In particular, the first grasping tooth 12 is interposed in the longitudinal direction X between the second grasping tooth 22 and the engagement tooth 31.[000329] The engagement tooth 31 is arranged coplanar with the first grasping tooth 12 and / or the second engagement tooth 22 and also lies on the grasping plane XY.[000330] The engagement tooth 31 has a greater transverse extension D1 considered along the transverse direction Y than the transverse extension D2 of the first grasping tooth 12.[000331] The engagement tooth 31 is configured to project along the transverse direction more than the first grasping tooth 12. The free end 31A of the engagement tooth 31 opposing the first retaining element 32 projects along the transverse direction more than the free end 12A of the first grasping tooth 12 opposing the first abutment element 13.[000332] The third portion PC is oscillatable with respect to the first PA and / or the second PB portion about an axis of oscillation parallel to the first grasping tooth 12 and / or the first engagement tooth 31 .[000333] The first grasping device 10 further comprises a connecting element 33 for fixing the first appendage 30 to the first grasping element 11. The connecting element 33 extends between the first grasping element 11 and the first appendage 30 parallel to and spaced from the grasping plane XY. The connecting element 33 has a profile adapted to follow the contour of a portion of the lateral flank of the stack of blanks 100. The retaining element 33 is arranged inclined with respect to the transverse direction Y and the longitudinal direction X so that the first appendage 30 is spaced with respect to the first grasping element 11 both along the transverse direction Y and along the longitudinal direction X. The retaining element 32 and the engagement tooth 31 are spaced with respect to the first abutment element 13 and respectively with respect to the first grasping tooth 12 in both the transverse direction Y and the longitudinal direction X.[000334] The first grasping device 10 further comprises a second grasping appendage 35 fixed to and integral with the second grasping element 12. The second grasping appendage 35 is spaced from the second grasping element 12 along the longitudinal direction X in such a way as to engage the stack of blanks in a fourth longitudinal portion PD spaced along the longitudinal direction X from the first longitudinal portion PA and the second longitudinal portion PB.[000335] The fourth longitudinal portion PD is oscillatable with respect to the second portion PB and the first portion PA.[000336] The fourth PD portion is oscillatable with respect to the first PA and / or the second PB portion about an axis of oscillation parallel to the second grasping tooth 16 and / or the second engagement tooth 36.[000337] The second grasping appendage 35 comprises a second engagement tooth 36 extending along the grasping direction Y and intended to engage a lower surface S of thestack of blanks 100 to support the stack of blanks 100. The second grasping appendage 35 further comprises a second retaining element 37 arranged transversely to the second engagement tooth 36, preferably perpendicularly to the second engagement tooth 35 and intended to retain the second lateral flank 100D of the stack of blanks 100. The second retaining element 37 extends along a vertical axis Z perpendicular to the longitudinal direction X and the grasping direction Y.[000338] The second retaining element 37 and the second engagement tooth 36 are configured to define an “L”-shaped grasping appendage 35, wherein the second engagement tooth 36 is provided at an end of the second retaining element 37 opposing the support structure 2.[000339] The second grasping appendage 35 is positioned so that the second grasping element 15 is interposed in the longitudinal direction X between the fourth grasping element 25 and the second grasping appendage 35. In particular, the third grasping tooth 16 is interposed in the longitudinal direction X between the fourth grasping tooth 26 and the second grasping tooth 35.[000340] The first grasping device 10 further comprises a second connecting element 38 for fixing the second appendage 35 to the second grasping element 15 extending between the second grasping element 15 and the second appendage 35 parallel to and spaced from the grasping plane. The second connecting element 38 has a profile adapted to follow the contour of a portion of the second lateral flank of the stack of blanks 100.[000341] The second retaining element 38 is arranged inclined with respect to the transverse direction Y and the longitudinal direction X so that the second appendage 35 is spaced with respect to the second grasping element 15 both with respect to the transverse direction Y and the longitudinal direction X. The second retaining element 37 and the engagement tooth 36 are spaced with respect to the second abutment element 17 and respectively with respect to the third grasping tooth 16 in both the transverse direction Y and the longitudinal direction X.[000342] The provision of inclined connecting elements allows the lateral edge of the stack of blanks to be contained, the first and second appendages to effectively abut with the first and second appendages, even panels with smaller transverse dimensions than the transverse dimensions of the panels engaged with the grasping elements. In addition, it is not necessary to provide engagement teeth with large transverse dimensions in order to effectively engage panels with the first and second appendages that have smallertransverse dimensions than the transverse dimensions of the panels engaged with the grasping elements.[000343] The first 33 and the second connecting element 38 are configured so that the first abutment element 13 and the second abutment element 17 are positioned at a transverse distance from each other less than the transverse distance between the first 32 and the second retaining element 37.[000344] The second engagement tooth 35 is arranged coplanar with the third grasping tooth 16 and / or the fourth grasping tooth 26.[000345] The second engagement tooth 36 has a greater transverse extension D3 considered along the transverse direction than the transverse extension D4 of the third grasping tooth 16.[000346] The second engagement tooth 36 is configured to project along the transverseY direction more than the third grasping tooth 16. The free end 36A of the second engagement tooth 36 opposing the second retaining element 37 projects along the transverse direction more than the free end 16Aof the third grasping tooth 16 opposing the second abutment element 17.[000347] The second grasping appendage 35 and the first grasping appendage 30 are configured in such a way that the first engagement tooth 31 and the second engagement tooth 35 are offset along the longitudinal direction, so as to engage the stack of blanks in longitudinally spaced portions. In the version shown, the third PC and the fourth PD longitudinal portion are both defined on the rear panel 105. In other versions, the third PC and the fourth PD longitudinal portion can be defined on distinct panels.[000348] The movement unit 1 further comprises a first splaying device 50 for moving the first grasping element 11 and the second grasping element 15 towards / away from each other along the grasping direction Y, as indicated by the arrow F in Figure 3, for moving the first grasping element 11 and the second grasping element 15 along the grasping directionY to adjust the transverse distance between the first grasping element 11 and the second grasping element 15 and for engaging / disengaging the stack of blanks, as further explained below. The first splaying device 50 comprises a worm gear 51 to which the first grasping element 11 and the second grasping element 15 are fixed and which can be driven to simultaneously move the first grasping element 11 and the second grasping element 15 along the grasping direction Y.[000349] The movement unit 1 comprises a second splaying device 52 for moving the third grasping element 21 and the fourth grasping element 25 towards / away from each otheralong the grasping direction Y to move between the third grasping element 21 and the fourth grasping element 25 along the grasping direction Y, as indicated by the arrow F1 in Figure 3, to adjust the transverse distance along the grasping direction Y and to engage / release the stack of blanks, as further explained below. The second splaying device 52 comprises a second worm gear 53 to which the third grasping element 21 and the fourth grasping element 25 are fixed and which can be driven to simultaneously move the third grasping element 21 and the fourth grasping element 25 along the grasping direction Y.[000350] The first 50 and the second splaying device 52 can be driven separately to adjust the distance between the first grasping element 11 and the second grasping element 15 and between the third grasping element 21 and the fourth grasping element 25, respectively. In some versions, the first splaying device 50 and the second splaying device 52 can be driven together to simultaneously adjust the distance between the first grasping element 11 and the second grasping element 15 and between the third grasping element 21 and the fourth grasping element 25 respectively to engage and move the stack of blanks or to release the stack of blanks. Driving the first splaying device 50 also simultaneously moves the first 30 and second grasping appendage 35 which are integral with the first 11 and second grasping element 15 respectively.[000351] The movement unit 1 further comprises an adjusting device 40 for moving the first grasping device 10 and / or the second grasping device 20 along the longitudinal direction X to adjust the longitudinal distance between the first grasping device 10 and the second grasping device 20 along the longitudinal direction X, as indicated by the arrow F2 in Figure 3.[000352] In this way, the movement unit 1 can be adapted to grasp and securely engage stacks of blanks of widely varying longitudinal dimensions.[000353] The pick-up head 6 can be driven via the movement member between a grasp configuration W, shown for example in Figures 3, 4 and 5, wherein the pick-up head 6 is inserted into the storage unit 200 in a position close to the support base 201 and the grasping elements 11 , 15, 21 , 25 are close to the stack of blanks 100 and an engagement configuration W’ shown for example in Figures 6, 7 and 9, wherein the grasping elements 11 , 15, 21 , 25 are pushed into contact with the stack of blanks 100 and the pick-up head 6 engages and retains the blanks of the stack of blanks 100. The movement member is configured to drive the first splaying device 50 and the second splaying device 52 to move the grasping elements 11 , 15, 21 , 25 along the grasping direction Y so as to bring thegrasping elements 11 , 15, 21 , 25 of the same grasping pair towards / away from each other. The movement member is configured to drive the first splaying device 50 and the second splaying device 52 to bring the grasping elements of the same grasping pair closer to each other to bring the pick-up head 6 from the grasping configuration W to the engagement configuration W’.[000354] In the grasping configuration W, the pick-up head 6 is positioned in the feeding unit 200, the grasping teeth 12, 16, 22, 26 and the engagement teeth 31 , 36 are almost in contact with the support base 201 and spaced from the stack 100, the abutment elements 13, 17, 23, 27 and the retaining elements 32, 37 are facing and spaced from the flanks of the stack of blanks 100.[000355] In the engagement configuration W’ the grasping teeth 12, 16, 22, 26 and the engagement teeth 31 , 36 are inserted below the lower face S’ of the stack of blanks 100 so that the lower blank is resting on the grasping teeth 12, 16, 22, 26 and the engagement teeth 31 , 36. In the engagement configuration W’ the abutment elements 13, 17, 23, 27 and the retaining elements 32, 37 are moved towards the flanks of the stack of blanks 100 and can abut the lateral flanks of the stack. Specifically, damping elements 23B, 27B are pushed into contact against the lateral flanks of stack 100 and are deformed upon contact with the flanks of the stack 100.[000356] In some versions the movement unit can be operated via a control unit 300, schematically shown in Figure 10. The control unit 300 is configured to control the operation of the movement unit. In particular, the control unit 300 is configured to control the operation of the splaying mechanism and the spacer mechanism. The control unit 300 is configured to control the movement of the grasping elements along the grasping direction Y, along the longitudinal direction X and along the vertical direction Z. The control unit 300 can be configured to control the movement of the pick-up head along the three orthogonal directions (X, Y, Z) and in rotation about an axis parallel AZ to the vertical direction Z.[000357] In operation, the pick-up head 6 is moved by the movement member so as to be inserted into the storage unit 200 and moved along the support arm 7A in the vertical direction Z towards the picked stack 100 and brought into the grasping configuration W. The support head 6 is moved so as to bring the grasping teeth 12, 16, 22, 26 and the engagement teeth 31 , 36 into contact with the support base 201 .[000358] This is followed by driving the movement member to bring the pick-up head 6 into the engagement configuration W’. The first splaying device 50 and the second splaying device 52 are driven by the movement member to move the grasping elements 11 , 15, 21 ,25 along the grasping direction Y in such a way as to bring the grasping elements 11 , 15, 21 , 25 of the same grasping pair towards each other. In this way, the grasping elements 11 , 15, 21 , 25 are brought closer to the respective flanks of the stack 100: the grasping teeth 12, 16, 22, 26 and the engagement teeth 31 , 36 are progressively inserted below the lower surface S’ of the stack 100, the abutment elements 13, 17, 23, 27 and the retaining elements 32, 37 are moved towards and subsequently pushed into contact with the flanks of the stack 100. The first 23B and the second damping element 27B are gradually deformed against the opposite lateral sides of the stack 100.[000359] In this way, the stack 100 is engaged with the pick-up head 6.[000360] The second grasping device 20 is positioned so that the first 23 and the second abutment element 27 engage the stack 100 at the recess 107 provided between the intermediate panel 104 and the end panel 106. Moving the second 21 and the fourth grasping element 25 towards the stack 100, the damping elements 23B, 27B are brought towards and subsequently pushed into contact against the flanks of the stack engaging the stack at the recess 107. By moving the second splaying device 52 towards the second 21 and the fourth grasping element 25, the damping elements 23B, 27B are pushed against the lateral flanks of the stack and deformed against the recess 107 of the stack, firmly engaging the stack.[000361] At the same time, the grasping teeth 12, 16, 22, 26 and engagement teeth 31 , 36 are progressively inserted below the lower surface S’ of the stack 100 engaging and supporting the stack 100.[000362] The first and second engagement teeth 31 , 36 engage the rear panel 105, in distinct longitudinal portions so as to avoid mutual interference between the engagement teeth 31 , 36.[000363] The transverse extension of the engagement teeth 31 , 36 is not a limitation on the mutual approach between the first 30 and second appendage 35 along the transverse direction Y. The first and second engagement teeth 31 , 36 may have a greater extension than the engagement teeth. The grasp of the stack of blanks is improved and even stacks having rear panels with limited dimensions can be effectively engaged.[000364] The stack of blanks is then engaged at four distinct longitudinal portions PA, PB, PC, PD, which can be oscillatable one in relation to the other, thus preventing unwanted oscillations of the panels of the blanks and ensuring that the grasp is firm.[000365] The first 11 and the second grasping element 15 engage the side panels 103, 103’ and the third 21 and the fourth grasping element 25 engage the blanks at the recess107. The third abutment element 23 and the fourth abutment element 27 engage the lateral flanks of the stack and the damping elements 23B, 27B are deformed against the respective lateral flank. In the version shown, the third and fourth abutment elements 23, 27 are placed at the recess 107 so that the damping elements 23B, 27B fit at least partially into the recess 107 and are deformed against the walls thereof, increasing the contact surface between the damping elements and the blank and improving the retention of the stack.[000366] By operating the first and second grasping devices separately, it is possible to engage with the movement unit stacks of blanks of various shapes and optimise the grasping of the stack itself.[000367] When the pick-up head 6 is in the engagement position W’ and the stack of blanks 100 is firmly engaged by the pick-up head 6, the latter can be moved to remove the stack 100 from the storage unit 200 and transport it to a feeding unit or a processing unit.[000368] The provision of grasping appendages allows for the firm engagement of blanks of various sizes. At the same time, the provision of damping elements improves the grasp of the blanks.

Claims

CLAIMS1 . Movement unit (1 ) for moving a stack of blanks (100) comprising:- a support structure (2);- a first grasping device (10) and a second grasping device (20) fixed to said support structure (2) and intended to engage the blanks (101) of said stack of blanks (100) and mutually spaced along a longitudinal direction (X) of said support structure (2) so as to engage said blanks (101) in a first longitudinal portion (PA) and in a second longitudinal portion (PB) spaced from said first longitudinal portion (PA) along said longitudinal direction (X);- said first grasping device (10) comprising a first grasping element (11) and a second grasping element (15) mutually facing and spaced along a grasping direction (Y) arranged perpendicularly with respect to said longitudinal direction (X) wherein at least one of the first grasping element (11) and the second grasping element (15) is movable along the grasping direction (Y) to adjust the distance between the first grasping element (11 ) and the second grasping element (15), and wherein at least one of the first grasping element (11) and the second grasping element (15) is provided with a first grasping tooth (12, 16) extending along said grasping direction (Y) towards the other of said second grasping element (15) or respectively said first grasping element (11) and intended to engage a lower surface (S) of said stack of blanks (100) for supporting said stack of blanks (100);- said second grasping device (20) comprising a third grasping element (21) and a fourth grasping element (25) mutually facing and spaced along said grasping direction (Y) wherein at least one of the third grasping element (21 ) and the fourth grasping element (25) is movable along the grasping direction (Y) to adjust the distance between the third (21) and the fourth grasping element (25), and wherein at least one of the third grasping element (21) and the fourth grasping element (25) is provided with a second grasping tooth (22, 26) extending along said grasping direction (Y) towards the other of said fourth grasping element (25) or respectively said third grasping element (22) and intended to engage a lower surface (S) of said stack of blanks (100) for supporting said stack of blanks;- wherein said first grasping device (10) comprises at least one grasping appendage (30) fixed to and integral with said first grasping element (11 )and spaced from said first grasping element (11) along said longitudinal direction (X) and configured to engage a third longitudinal portion (PC) of said stack of blanks (100) spaced along said longitudinal direction (X) from said first longitudinal portion (PA) and from said second longitudinal portion (PB), and oscillatable with respect to said second longitudinal portion (PB) and / or said first longitudinal portion (PA).

2. Movement unit according to claim 1 wherein said third portion (PC) is oscillatable about an oscillation axis parallel to said first (12, 16) and / or said second grasping tooth (22, 26).

3. Movement unit according to any one of the preceding claims wherein said grasping appendage (30) comprises a engagement tooth (31) extending along said grasping direction (Y) and intended to engage a lower surface (S) of said stack of blanks (100) for supporting said stack of blanks (100).

4. Movement unit according to the preceding claim wherein said grasping appendage (30) further comprises a retaining element (32) arranged transversely to said engagement tooth (31), preferably perpendicularly to said engagement tooth (31) and intended to retain a first flank (100C) of said stack of blanks (100).

5. Movement unit according to the preceding claim wherein said retaining element (32) is arranged to extend along a vertical axis (Z) perpendicular to said longitudinal direction (X) and said grasping direction (Y).

6. Movement unit according to any one of the preceding claims wherein said grasping appendage (30) is positioned so that said first grasping tooth (12) of said first grasping element (11) is interposed in the longitudinal direction (X) between said second grasping tooth (22) of said third grasping element (21) and the engagement tooth (31 ) of said grasping appendage (30).

7. Movement unit according to any one of the preceding claims and further comprising a second appendage (35) fixed to and integral with the second grasping element (15) and spaced from said second grasping element (15) along said longitudinal direction (X) and along said grasping direction (Y) said second appendage being configured to engage a fourth portion (PD) of said stack of blanks (100) spaced along said longitudinal direction (X) from said first portion (PA) and from said second portion (PB) and from said third portion (PC) said fourth portion (PD) being oscillatable with respect to said second portion (PB) and said first portion (PA).

8. Movement unit according to the preceding claim wherein said second graspingappendage (35) and said first grasping appendage are configured so that the first engagement tooth (31) and the second engagement tooth (36) are offset along said longitudinal axis.

9. Movement unit according to the preceding claim wherein said second appendage (35) is positioned so that said first grasping tooth (12) is interposed in the longitudinal direction (X) between said second grasping tooth (22) and the second engagement tooth (36).

10. Unit according to any one of the preceding claims, wherein at least one of said first, second, third and fourth grasping elements (11 , 15, 21 , 25) comprises an abutment element (13, 17, 23, 27) interposed between said support structure (2) and the respective grasping tooth (12, 16, 22, 26), and arranged to abut a flank (100C, 100D) of said stack of blanks (100), said abutment element (13, 17, 23, 27) extending transversally to the respective grasping tooth (12, 16, 22, 26) of said grasping element (11 , 15, 21 , 25), preferably substantially perpendicularly to the respective grasping tooth (12, 16, 22, 26) of said grasping element (11 , 15, 21 , 25) so as to define a grasping element configured like an “L”.11 . Unit according to the preceding claim wherein at least one of said first, second, third or fourth abutment element (23, 27) comprises a support body (23A, 27A) and a damping element (23B, 27B) coupled to said support body (23A, 27A) and intended to abut said stack of blanks and having a convex curved profile towards said stack of blanks, so as to improve the abutment with said stack of blanks, said damping element (23B, 27B) preferably being made of a material which yields to deform upon contact with said stack of blanks (100).

12. Unit according to one of the preceding claims wherein said first (12) and said second grasping tooth (22) are coplanar and define a grasping plane XY, said first grasping element (11) comprising a connecting element (33) extending between said first grasping element (11) and said appendage (30) parallel to said grasping plane (XY) spaced from said grasping plane (XY) said connecting element (33) having a profile adapted to follow the profile of a flank portion of said stack of blanks (100).

13. Movement unit according to any one of the preceding claims and further comprising a splaying device (50) for moving at least one of the first grasping element (11 ) and the second grasping element (15) along the grasping direction (Y) to adjust the transverse distance between the first grasping element (11) and the secondgrasping element (15).

14. Packaging apparatus for packing articles into boxes by folding a blank and comprising a movement unit according to one of the preceding claims.

15. Method for moving a stack of blanks comprising providing a movement unit (1) having a support structure (2) provided with a first grasping device (10) and a second grasping device (20) mutually spaced along a longitudinal direction (X) of said support structure (2) and configured to engage said blanks (101) in a first longitudinal portion (PA) and a second longitudinal portion (PB) spaced along said longitudinal direction (X); said first grasping device (10) comprising a first grasping element (11 ) and a second grasping element (15) mutually facing and spaced along a grasping direction (Y) arranged perpendicularly with respect to said longitudinal direction (X) wherein at least one of the first grasping element (11) and the second grasping element (15) is movable along the grasping direction (Y) to adjust the distance between the first grasping element (11) and the second grasping element (15), and wherein at least one of the first grasping element (11) and the second grasping element (15) is provided with a grasping tooth (12, 16) extending along said grasping direction (Y) towards the second grasping element (15) or respectively towards the first grasping element (11) and intended to engage a lower surface (S) of said stack of blanks (100) for supporting said stack of blanks (100); said second grasping device (20) comprising a third grasping element (21) and a fourth grasping element (25) mutually facing and spaced along said grasping direction (Y) wherein at least one of the third grasping element (21 ) and the fourth grasping element (25) is movable along the grasping direction (Y) to adjust the distance between the third (21) and the fourth grasping element (25), and wherein at least one of the third grasping element (21) and the fourth grasping element (25) is provided with a grasping tooth (22, 26) extending along said grasping direction (Y) towards the fourth grasping element (25) or respectively the third grasping element (22) and intended to engage a lower surface (S) of said stack of blanks (100) for supporting said stack of blanks; wherein said first grasping device (10) comprises at least one grasping appendage (30) fixed to and integral with said first grasping element (11 ) and spaced from said first grasping element (11) along said longitudinal direction (X) and configured to engage a third longitudinal portion (PC) of said stack of blanks (100) spaced alongsaid longitudinal direction (X) from said first longitudinal portion (PA) and said second longitudinal portion (PB); said method including moving said support structure (2) towards said stack of blanks (100); moving at least one of said first (11 ) and said second (15) grasping elements along said grasping direction (Y) and at least one of said third (21) and said fourth (25) grasping elements along said grasping direction (Y) to bring said grasping elements closer to said stack of blanks (10) so as to insert said grasping teeth (12, 16, 22, 26) below said lower surface (S) of said stack of blanks (100) to support said stack of blanks (100) and to abut said third longitudinal portion (PC) with said at least one appendage to prevent an oscillation of said third portion (PC) with respect to said first longitudinal portion (PA) and / or said second longitudinal portion (PB).

16. Method according to the preceding claim wherein said grasping appendage (30) comprises an engagement tooth (31 ) extending along said grasping direction (Y), and said moving comprises engaging said lower surface (S) of said stack of blanks (100) with said engagement tooth (31) for supporting said stack of blanks (100) and to prevent an oscillation of said third portion (PC) relative to said first portion (PA) and / or said second portion (PB).

17. Method according to claim 15, or 16, wherein said grasping appendage (30) further comprises a retaining element (32) arranged transversely to said engagement tooth (31), preferably perpendicularly to said engagement tooth (31), and said moving comprises retaining a flank (N) of said stack of blanks (100) with said retaining element.

18. Method according to any one of claims 15 to 17 wherein at least one of said first, second, third and fourth grasping elements (11 , 15, 21 , 25) comprises an abutment element (13, 17, 23, 27) interposed between said support structure (2) and the respective grasping tooth (12, 16, 22, 26) and wherein said moving comprises striking a flank (100C, 100D) of said stack of blanks (100) with said abutment elements.

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