Packaging unit for packaging articles in boxes and method for packaging articles in boxes

Abstract

A packaging unit for packaging articles in boxes includes a mandrel, a movement device, a feeding device, a first abutment surface, and a retaining device. The mandrel is configured to accommodate at least one of said articles inside it. The movement device is configured to move said mandrel along a movement trajectory. The feeding device is configured to feed at least one blank along a feeding trajectory which intersects said movement trajectory towards said mandrel to form one of said boxes around said mandrel. The first abutment surface is defined on said mandrel as the surface of said mandrel intended to abut said blank when positioned in said movement trajectory. The retaining device is displaceable between an operating position in which said retaining device approaches said first abutment surface to retain said blank against said first abutment surface and a non-operating position in which said retaining device is spaced apart from said first abutment surface.

Claims

1. A packaging unit for packaging articles in boxes, comprising: a mandrel configured to accommodate at least one of said articles therein, a movement device configured to move said mandrel along a movement trajectory, a feeding device configured to feed at least one blank along a feeding trajectory towards said mandrel to form one of said boxes around said mandrel, a first abutment surface of said mandrel to abut said blank when positioned in said movement trajectory, and a retaining device displaceable between an operating position and a non-operating position, wherein: the feeding trajectory intersects said movement trajectory, in the operating position said retaining device approaches said first abutment surface to retain said blank against said first abutment surface, and in the non-operating position said retaining device is spaced apart from said first abutment surface, the packaging unit further comprising: an actuation member configured to displace said retaining device along an actuation trajectory to bring said retaining device towards said operating position, wherein said actuation trajectory comprises a transverse stroke arranged transversely to the movement trajectory of said mandrel, and a thrust stroke arranged parallel to the movement trajectory of said mandrel.

2. The packaging unit according to claim 1, wherein: an advancement plane is defined by said mandrel when moved along said movement trajectory, and said movement device is configured to move said mandrel along the advancement plane and said transverse stroke is parallel to said advancement plane.

3. The packaging unit according to claim 1, wherein: an advancement plane is defined by said mandrel when moved along said movement trajectory, and said movement device is configured to move said mandrel along the advancement plane and said transverse stroke is perpendicular to said advancement plane.

4. The packaging unit according to claim 1, wherein: said actuation member is configured to displace said retaining device along said thrust stroke in a direction that is opposite with respect to the movement trajectory of said mandrel to displace said retaining device into said operating position.

5. The packaging unit according to claim 1, wherein said movement device is configured to move said mandrel along a movement trajectory comprising a portion of circular trajectory.

6. The packaging unit according to claim 1, wherein said actuation trajectory comprises a further transverse stroke arranged radially with respect to the movement trajectory of said mandrel.

7. The packaging unit according to claim 6, wherein said feeding device is configured to move said blank along a feeding trajectory comprising at least one radial feeding stroke arranged radially with respect to the movement trajectory of said mandrel.

8. The packaging unit according to claim 7, each said at least one radial feeding stroke having a direction opposed to said further transverse stroke.

9. The packaging unit according to claim 1, wherein said retaining device is operatively associated with said movement device to carry said retaining device along said movement trajectory.

10. The packaging unit according to claim 1, further comprising a folding device to abut said blank and configured to cooperate with said mandrel to fold said blank around said mandrel when said blank is positioned between said mandrel and said folding device.

11. The packaging unit according to claim 10, said folding device comprising: a first folding element and a second folding element arranged to respectively abut a first panel and a second panel of said blank, wherein said retaining device is interposed in said operating position between said first folding element and said second folding element for retaining an intermediate panel of said blank interposed between said first panel and said second panel.

12. The packaging unit according to claim 11, wherein said retaining device is configured to couple to said intermediate panel.

13. A method for packaging articles in boxes comprising: a) depositing at least one of said articles in a mandrel, b) moving said mandrel along a movement trajectory, c) displacing at least one blank by a feeding device and positioning said blank along said movement trajectory of said mandrel in an advanced position with respect to said mandrel, d) abutting said first blank with a first abutment surface of said mandrel, e) retaining said blank against said first abutment surface with a retaining device, f) decoupling said blank from said feeding device, g) displacing said blank and said mandrel along said movement trajectory while said blank is retained against said first abutment surface, and h) displacing said retaining device between an operating position in which said retaining device retains said blank against said first abutment surface of said mandrel and a non-operating position in which said retaining device is spaced apart from said first abutment surface, wherein said step h) of displacing said retaining device comprises displacing said retaining device along a transverse stroke arranged transversely to the movement trajectory of said mandrel, and displacing said retaining device along a thrust stroke arranged parallel to the movement trajectory of said mandrel.

14. The method according to claim 13, wherein said step e) retaining said blank against said first abutment surface occurs prior to said step f) decoupling said blank from said feeding device.

15. The method according to claim 13, wherein said step e) retaining said blank against said first abutment surface occurs after said step d) abutting said blank with said first abutment surface of said mandrel.

16. The method according to claim 13, further comprising: providing a folding device configured to cooperate with said mandrel to fold said blank around said mandrel when said blank is positioned between said mandrel and said folding device, and abutting said blank with said folding device to fold said blank around said mandrel.

17. The method according to claim 16, wherein said step e) retaining is provided prior to said step of abutting said blank with said folding device, and wherein said step f) decoupling is provided after said step of abutting said blank with said folding device.

Description

(1) The characteristics and advantages of the invention will become clearer from the detailed description of a preferred embodiment thereof, by way of non-limiting example, with reference to the appended drawings wherein:

(2) FIGS. 1 and 2 are two schematic plan views of an embodiment example of a packaging unit in accordance with the present solution;

(3) FIGS. 3-5 are partial schematic views of a folding device and of a mandrel of the packaging unit of FIG. 1 and of a blank in three distinct positions of use;

(4) FIGS. 6-7 are partial schematic views of a folding device of the packaging unit of FIG. 1 respectively in a first position and in a second position;

(5) FIG. 8 is a schematic figure of a folding device and of a mandrel of the packaging unit of FIG. 1 and of a blank in a position of use;

(6) FIG. 9 is a schematic view of a blank usable in the packaging unit of FIG. 1;

(7) FIGS. 10A and 10B are two interrupted graphs of a movement trajectory of the packaging unit of FIG. 1;

(8) FIG. 11 is a schematic view of a portion of the packaging unit of FIG. 1;

(9) FIG. 12 is a schematic view showing the movement of a retaining element of the packaging unit of FIG. 1;

(10) FIGS. 13 and 14 are truncated perspective views of a further version of a packaging unit according to the invention;

(11) FIG. 15 is a perspective view of the packaging unit of FIG. 14 with some parts removed for clarity's sake.

(12) In the accompanying figures, a packaging unit made in accordance with this solution is indicated as a whole with 100 and 100. In particular, a first version of the packaging unit 100 is shown in FIGS. 1-12, while a further version of the packaging unit 100 is shown in FIGS. 13-15 which differs from that shown in FIGS. 1-12 solely in the configuration of the retaining device 60, the remaining parts being identical to those of the packaging unit 100. Therefore, with regard to the further packaging unit 100, only the retaining device 60 will be described below for brevity's sake, the parts of which corresponding to the retaining device 60 of FIGS. 1-12 will be indicated with the same numerical references followed by a superscript, for the remaining parts reference will be made to what will be described with reference to FIGS. 1-12 and these parts will be indicated with the same numerical references and not described in detail.

(13) The packaging unit 100, 100 is of the wrap-around type, performing the packaging by wrapping a box around at least one article 1 to be packaged. In the present example the article 1, better visible in FIG. 3 or 4, consists of one or more flexible bags, filled with predetermined quantities of bulk products in the form of a discrete particulate consisting of granules and/or corn flakes and suitably sealed. The box 2 is formed by wrapping a blank 7 around a mandrel 10 bearing the article 1, as better clarified below.

(14) The packaging unit 100, 100 is fed by a straight conveyor belt 101 on which the articles 1 to be packaged are conveyed, which in the present example consist of the bags described above, coming from the respective filling and sealing plant. The conveyor belt 101 transports the articles 1 to a first unloading end 102 at which the articles 1 are picked up by a transfer carousel 103 which is provided to pick up an article 1 to be packaged from the conveyor belt 101 and transfer it to the packaging unit 100, 100 in which the execution of a wrapping step of a box is provided for, as better clarified below.

(15) The packaging unit 100, 100 comprises in its more general units a forming carousel 3 which is provided to receive the articles 1 from the transfer carousel 103 and to form a box 2, a feed carousel 5 for feeding blanks 7 to the forming carousel 3 and an outlet carousel 6, intended to pick up the boxes 2 formed by the forming carousel 3 and to deposit them on an evacuation belt 8 through which the boxes 2 are transported to subsequent processing units provided in the packaging unit 100, 100.

(16) The forming carousel 3, the feed carousel 5 and the outlet carousel 6 are brought into rotation, by means of respective movement devices not shown, in order to be rotatable about respective axes of rotation substantially parallel to a vertical direction, indicated in the figures generally with Z perpendicular to the plane of FIGS. 1 and 2.

(17) The forming carousel 3 is provided with a plurality of mandrels 10, each mandrel 10 is configured to accommodate at least one of the articles 1 inside it and is operatively connected to a movement device 50 of the forming carousel 3 to be displaced along a movement trajectory M at a desired movement speed VM, as better explained below. The movement trajectory M lies on an advancement plane 200 of the mandrel 10 and is a line oriented in the shape of an arc of circumference. The movement speed VM is a vector having at each point a direction tangent to the movement trajectory M and a desired modulus M2 which is constant along the movement trajectory M as best schematized in FIG. 10A-10B. The advancement plane of the mandrel 200 has an orientation 200 in an orthogonal Cartesian reference system Z.

(18) The mandrel 10 comprises a first unit 11 and a second unit 12, which are distinct and separated from each other, both mounted on an arm not extended radially by the movement carousel 3 and passing below a fixed work surface 9 of the packaging unit 100, 100.

(19) The first unit 11 and the second unit 12 are positioned so as to define an accommodation seat 13 for an article 1 to be transported. Advantageously, the first 11 and the second unit 12 are displaceable with respect to each other so as to define an accommodation seat 13 for the articles 1 with variable dimensions.

(20) The mandrel 10 further comprises a first abutment surface 10A defined as the surface of the mandrel 10 intended to be the first to abut the blank 7 when the latter is positioned in the movement trajectory M and a folding surface 10B opposed to the first abutment surface 10A intended to abut the outer flap and the inner flap of the blank when the latter is folded around the mandrel 10, as better explained below. The first abutment surface 10A is the surface of the mandrel 10 provided in the further advanced position along the movement trajectory M. The folding surface 10B is the surface of the mandrel 10 provided in the further backward position along the movement trajectory M.

(21) The feeding carousel 5 comprises a plurality of feeding devices 30, each configured to feed a blank 7 towards a mandrel 10. Each feeding device 30 is configured to pick up a single blank 7 from a group of blanks stacked in a hopper 700 and to bring it to the forming carousel 3 and is configured to feed the blank 7 along a feeding trajectory which intersects the movement trajectory M. Each feeding device 30 comprises a plurality of retaining elements 31 arranged to retain the blank 7 in different portions thereof. Each retaining element 31 comprises a suction cup operatively connected to a suction device, not visible in the figures, and arranged to releasably retain a desired portion of a blank, as better clarified below. An application device 701 is also provided which is intended to apply a desired amount of glue on an edge portion of a flap 7D of the blank 7, when the blank 7 is retained on a retaining device 60 before feeding it to the forming carousel 3.

(22) The blank 7 is made of cardboard with a thickness comprised between 0.4 and 0.8 mm, in this case about 0.5 mm, and is suitably shaped to form a box 2 when folded around the mandrel 10. For this purpose, folding lines 70 are obtained on the blank 7 that divide the blank 7 into a plurality of panels 71 intended to form, alone or in combination with each other, the different faces of the box 2. The folding lines 70 are preferably creases and each pair of adjacent panels 71 is oscillatable around a respective folding line 70 that separates them. In particular, as better visible in FIG. 9, in the blank 7 are identified an intermediate panel 7C, intended to be abutted as first by the mandrel 10, as well as a first and a second panel 7A, 7B that extend respectively on two opposed sides of the intermediate panel 7C and are separated therefrom by respective folding lines 70, and a plurality of flaps 73, 7D, 7E. The first and second panels 7A, 7B are intended to form two opposed faces of the box 2. The first and second panels 7A, 7B are intended to be folded on the mandrel 10 on opposite sides with respect to the advancement plane 200, as better clarified below. The flaps 73, 7D, 7E are separated by an adjacent panel by means of a folding line and are adapted to overlap with other flaps of the plurality of flaps to form the box 2.

(23) In particular, the blank 7 is shaped such that, once wrapped at least partially around the mandrel 10, the two flaps 7D, 7E are overlappable on each other when folded towards each other along the corresponding folding line 70.

(24) The blank 7 is shaped such that, once wrapped at least partially around the mandrel 10, the two flaps 7D, 7E overlap each other abutting the mandrel 10 on a folding surface 10B thereof. The flap 7D, once this overlap has been made, will be located outside the partially closed box; this flap 7D is the so-called outer flap 7D. In a completely similar way, the flap 7E, once such overlap has been made, will be located between the outer flap 7D and the inside of the partially closed box; such flap 7E is the so-called inner flap 7E. The inner flap and the outer flap are shaped so as to overlap each other in an overlapping portion.

(25) The packaging unit 100, 100 further comprises a folding device 20, better visible in FIGS. 6 and 7, intended to abut the blank 7 and configured to cooperate with the mandrel 10 to fold the blank 7 around the mandrel 10 and an actuation device 40 configured to displace the folding device 20 along at least one folding stroke P which, in the version shown, is defined on the movement trajectory M of the mandrel 10.

(26) The packaging unit 100, 100 further comprises a guide device 15, provided immediately downstream of the folding device 20 and comprising a first guide plate 16 and a second guide plate 17 that are mutually facing and defining a housing 18 for a box to be formed. The first guide plate 16 and the second guide plate 17 extend for a guide stroke G of the movement trajectory M. The first guide plate 16 and the second guide plate 17 extend respectively between a first end 16A, 17A and a second end 16B, 17B, the first end 16A, 17A being provided in a backward position with respect to the second end 16B, 17B and they allow to maintain the shape of the box 2 being formed avoiding unwanted openings thereof. The first end 16A, 17A of the first 16 and second plate 17 define the inlet for the housing 18 through which the mandrel 10 enters the housing 18.

(27) The packaging unit 100 further comprises a retaining device 60, shown in greater detail in FIGS. 6 and 12, displaceable along an actuation trajectory between an operating position E1, shown in FIG. 6, in which the retaining device 60 is approached to the first abutment surface 10A of the mandrel to retain the blank 7 against the first abutment surface 10A and a non-operating position in which the retaining device 60 is spaced apart from the first abutment surface 10A.

(28) The retaining device 60 comprises a lamina 61 having a retaining surface 62 shaped so as to couple with shape coupling with the first abutment surface 10A. In other words, the retaining device 60 is configured so that the lamina 61 is positioned in an advanced position with respect to the mandrel 10 along the movement trajectory M.

(29) The retaining device 60 is positioned so as to be interposed along the vertical axis Z, in the operating position E1, between the first folding element 21 and the second folding element 22 for retaining the intermediate panel 7C of the blank 7. The lamina 61 is configured to couple to the intermediate panel 7C.

(30) The packaging unit 100 further comprises an actuation member 63 intended to move the retaining device 60 between the operating position E1 and the non-operating position. In the operating position E1 of the retaining device 60 the blank 7 is retained against the first abutment surface 10A of the mandrel 10 while in the non-operating position of the retaining device 60 it is moved away from the blank 7.

(31) As can be seen from FIG. 11, the retaining device 60 is operatively associated with the mandrel 10 so as to be carried, via the movement device 40, together with the mandrel 10, along the movement trajectory M. The retaining device 60 is also movable with respect to the mandrel 10 in order to be displaced between the operating position E1 and the non-operating position.

(32) In the version shown, the lamina 61 is constrained at a first end 61a thereof to a support element 64 interposed between the lamina 61 and the actuation element 63 so as to be displaced between the operating position E1 and the non-operating position along an actuation trajectory having a transverse component Tx transverse to the movement trajectory M and a thrust component Ty parallel to the movement trajectory M. The transverse component Tx and the thrust component Ty are perpendicular to each other and parallel to the advancement plane 200.

(33) In the version shown in FIGS. 1 to 12 the lamina 61 is constrained in a fixed manner to the support element 64, while in the version shown in FIGS. 13-15 the lamina 61 is constrained in an adjustable manner to the support element 64, as better clarified below.

(34) With reference to FIGS. 13-15 the retaining device 60 comprises a lamina 61 with a retaining surface 61A with a shape analogous to the first abutment surface 10A of the mandrel 10 and hooked by an adjustment device 65 in an adjustable manner to the support structure 64. In this way the lamina 61 is displaceable with respect to the support structure 64 along a direction transversal to the first abutment surface 10A of the mandrel.

(35) The adjustment device 65 comprises a pair of adjustment elements 65 spaced apart along a longitudinal direction of the lamina 61. Each adjustment element 65 comprises a pin 66 extended between the lamina 61 and the support structure 64 to hook the lamina 61 and the support structure 64 and a spring 67 hooked at a first end thereof to the support structure 64 and at an opposed end thereof to the pin 66 and deformable to allow the displacement of the lamina 61 with respect to the support structure 64.

(36) Other adjustment elements can be used in other versions.

(37) The packaging unit 100, 100 further comprises a closing device 80 to fold two flaps of the blank onto the mandrel 10. As can be seen from FIG. 11, the closing device 80 is operatively associated with the mandrel 10 so as to be carried, via the movement device 50, together with the mandrel 10, along the movement trajectory M. The closing device 80 is also movable with respect to the mandrel 10 in order to be displaced between the operating position E1 and the non-operating position.

(38) The closing device 80 comprises a displacement member, not visible in the figures, and an abutting element 41 movable with respect to the mandrel 10 between a rest position in which the abutting element 41 is remote with respect to the mandrel 10 and a pressure position, in which the abutting element 41 is in a position such as to press the outer flap 7D on the inner flap 7E and against a folding surface 10B of the mandrel 10. The displacement member moves the abutting element 41 between the rest, folding and pressure positions.

(39) Said displacement member comprises an articulated arm that actuates the displacement of the abutment element 41 between the rest and pressure positions.

(40) The abutment element 41 comprises a support element 44 constrained to the displacement member, two compensating elements not shown in the Figures, and a pressure plate 42 having a pressure surface 42A intended to abut the mandrel 10 in its folding surface 10B.

(41) The abutting element 41, in passing from the rest position to the folding position and then to the pressure position, approaches the mandrel 10 from the side of the outer 7D and inner 7E flaps of the blank 20 until it meets the outer flap 7D and pushes it against the mandrel 10 until it abuts the mandrel 10 itself on its folding surface 10B together with the inner flap 7D.

(42) The approach of the abutment element 41 to the mandrel 10 from the rest position to the pressure position takes place with a straight trajectory D that is inclined with respect to the folding surface 10B of the mandrel 10. Advantageously, the folding trajectory D is inclined with respect to the advancement plane of the mandrel 10.

(43) As soon as the abutment element 41, and in particular the pressure plate 42 with its pressure surface 42A, contacts the mandrel 10 on its folding surface 10B, by pressing the outer flap 7D on the inner flap 7E and against the folding surface 10B, the compensating elements orient the abutment element 41 so that the pressure surface 42A and the folding surface 10B abut so as to be parallel.

(44) In this way in the pressure position any misalignments between the folding surface 10B of the mandrel 10 and the abutment element 41 are corrected.

(45) In the version shown the packaging unit 100, 100 comprises a plurality of mandrels 10, a plurality of retaining devices 60, a plurality of closing devices 80 movable along the movement trajectory M.

(46) In the version shown, a plurality of equipment 110 movable along the movement trajectory M can be identified in the forming carousel 3, each equipment 110 comprising a mandrel 10, a retaining device 60 and a closing device 80. In this way the mandrel 10, the retaining device 60 and the closing device 80 of the same equipment 110 are displaced together along the movement trajectory M, and furthermore the retaining device 60 and the closing device 80 can be moved with respect to the mandrel 10 to retain and fold the blank 7. The equipment 110 of the plurality of equipment are carried by the movement device so as to interact in succession with various devices provided in the packaging unit to form a box around a mandrel.

(47) Each mandrel 10 is carried along the movement trajectory M between a receiving zone 202, in which the mandrel 10 receives an article 1 from the transfer carousel 103, an abutment zone 203, in which the mandrel 10 abuts a blank 7 supplied by the feeding device 30 in a first abutment position R1, a forming zone 204, in which the blank 7 is folded on the mandrel so as to form a box 2 containing the article 1, an unloading zone 205, in which the box 2 containing the article 1 is deposited on the outlet carousel 6 and, finally, a return zone 206 in which the mandrel 10 is returned to the receiving zone 202. From the outlet carousel 6, the box 2 is then deposited on the evacuation belt 8 to be transported to the subsequent processing stations.

(48) The folding device 20, better visible in FIGS. 6 and 7, comprises a first folding element 21 and a second folding element 22 which are arranged to abut respectively the first panel 7A and the second panel 7B of the blank 7. The first and second folding elements 21, 22 are positioned so as to respectively abut a first 7A and a second panel 7B of the blank 7 which are positioned on opposite sides of the blank 7 with respect to the advancement plane 200 defined by the mandrel 10.

(49) Each folding element 21, 22 comprises a folding portion 21A, 22A shaped to interact with the blank 7, and a first and a second movement member 21D, 22D for transmitting the motion from a respective actuation motor 42 respectively to the first and the second folding element 21, 22. The first and the second movement member 21D, 22D comprise a plurality of mutually hinged levers to form an articulated polygon movement member.

(50) The first 21 and the second folding element 22 are associated respectively with the first 16 and the second guide plate 17. This measure increases the stability of the folding device 20 and optimises the folding of the box avoiding unwanted openings.

(51) Each folding portion 21A, 22A defines a respective first impact surface 21C, 22C of the blank 7 against the respective folding element 21, 22. The first impact surface 21C, 22C is the surface of each folding element 21, 22 which abuts the blank 7 as first when positioned on the movement trajectory M.

(52) The first impact surface 21C, 22C has a rounded shape, convex towards the blank 7 with a curvature such as to form with the blank an angle of about 45 and is made of low friction coefficient material, usually plastic or metallic material. The first impact surface 21C, 22C is made of stainless steel.

(53) The actuation device 40 is configured to move the folding device 20 alternately in a direction concordant to the movement trajectory M and in a direction opposite to the movement trajectory M.

(54) In particular, as better schematized in FIGS. 10A and 10B, the folding device 20 is moved along the folding stroke P in a direction concordant to the movement trajectory M with an accompanying speed Va to fold the blank 7 on the mandrel 10 and along the folding stroke P in a direction contrary to the movement trajectory M with a return speed VR so as to be brought towards the mandrel 10.

(55) The folding device 20 is movable along the folding stroke P between a first position P1 which corresponds to the further backward position of the folding device 20 along the movement trajectory M and a second position P2 which corresponds to the most advanced position of the folding device 20 along the movement trajectory M. The second position P2 is provided respectively near the first end 16A, 17A of the first 16 and the second plate 17.

(56) The actuation device 40 moves the folding device 20 from the second position P2 to the first position P1 with a return speed VR to bring it towards the mandrel 10 and moves the folding device 20 from the second position P2 to the first position P1 with an accompanying speed concordant to the movement speed VM to fold the blank 7.

(57) In particular, the actuation device 40 moves the folding device 20 in succession along a first portion PA of the folding stroke P between the first position P1 and an abutment position R2 and along a second portion PB of the folding stroke P between the abutment position R2 and the second position P2. In the first portion PA the folding device 20 is spaced apart from the mandrel 10 and from the blank 7, while in the second portion PB the folding device 20 is in contact with the blank 7.

(58) In the first portion PA, the distance between the folding device 20 and the mandrel 10 is progressively reduced up to the abutment position R2 in which the folding device 20 abuts the blank 7. The abutment position R2 is provided downstream of the first abutment position R1. In the second portion of the folding stroke PB the folding device is at least overlapped on the mandrel 10.

(59) In the first position P1, which is provided downstream of the first abutment position R1, the folding device 20 is spaced apart from the mandrel 10 and from the blank 7 and positioned at an advanced position with respect to the mandrel 10. In the second position P2 the folding device is overlapped on the mandrel 10.

(60) The operation of the packaging unit 100, 100 is now explained. An article 1 is deposited on a mandrel 10 at the receiving zone 202 and moved together with the mandrel 10 along the movement trajectory M. The mandrel 10 is moved along the movement trajectory M at a movement speed VM having modulus M2.

(61) The feeding device 30 feeds a blank 7 towards the movement carousel 3, positioning it in a feeding position A1 provided along the movement trajectory M in an advanced position with respect to the mandrel 10 and moves the blank 7 for a stroke of the movement trajectory M.

(62) The mandrel 10 in movement along the trajectory M approaches the blank 7 until, in the first abutment position R1, the first abutment surface 10A of the mandrel 10 abuts the blank 7. Subsequently, the mandrel 10 moves along the feeding stroke A2 together with the blank 7 and the feeding device 30 up to a retaining position R4 in which the retaining device 60, 60 is positioned in the operating position E1 and engages the intermediate panel 7C of the blank 7 to retain it on the mandrel 10. In the retaining position R4 the lamina 61, 61 of the retaining device 60, 60 presses the blank against the first impact surface 10A of the mandrel 10. Since the retaining device 60, 60 is mounted integrally to the mandrel 10, the retaining device 60, 60 is dragged together with the mandrel 10 along the movement trajectory M continuing to retain the blank against the mandrel 10 itself.

(63) The operating member 63, 63 displaces the retaining device 60 towards the blank 7 to bring it against the intermediate panel 7C of the blank 7, as schematized in FIG. 12. The presence of the retaining device 60, 60 makes it possible to make the positioning of the blank on the mandrel 10 more precise so as to fold the blank around the mandrel in an extremely precise manner. In addition, if the adjustment device is provided, this retention is very precise even in the case of misalignments.

(64) From the retaining position R4 the mandrel 10 continues to transport the blank 7 along the movement trajectory M up to a release position R3 in which the feeding device 30 releases the blank 7. From the release position R3 the mandrel 10 transports the blank 7 up to the abutment position R2 where the folding device 20 abuts the blank 7. The presence of the retaining device 60, 60 allows the blank 7 to be released from the retaining device 60, 60 upstream of the abutment position R2.

(65) From the abutment position R2 to the second position P2 the mandrel and the folding device both move along the movement trajectory M folding the blank 7 around the mandrel 10. In the second position P2 the folding device 20 stops while the mandrel 10 continues its movement along the movement trajectory M coming out of the folding device 20 to enter the housing 18 defined between the first guide plate 16 and the second guide plate 17.

(66) In the abutment position R2 the folding device 20 is moving along the folding stroke P at the accompanying speed Va which is parallel to the movement speed VM and has modulus M1 lower than the modulus M2 of the movement speed VM. It is noted that when the folding device 20 abuts the blank 7, the folding device 20 is moved in a manner concordant to the mandrel 10 even if at a speed with a lower modulus and this prevents there being kickbacks on the blank 7 and sudden strokes being imparted on the same.

(67) Since the accompanying speed Va of the folding device 20 has a modulus M1 lower than the further modulus M2 of the movement speed VM, in the second portion PB of the folding stroke P a relative motion between the folding device 20 and the mandrel 10 and, therefore, between the folding device 20 and the blank 7 is generated since the latter is integral with the mandrel 10.

(68) In other words, since in the second folding stroke PB the folding device 20 is slower than the mandrel 10 it progressively slides along the blank 7 in the direction opposed to the movement trajectory M, effectively folding the blank 7 around the mandrel 10. The folding device 20 abuts the blank 7 in the abutment position R2 and accompanies the mandrel up to the second position P2, that is up to the inlet of the housing 18 progressively folding the blank 7 on the mandrel 10.

(69) Between the abutment position R2 and the second position P2 a detachment position R5 can be provided in which the retaining device 60 moves away from the mandrel 10 and then from the blank 7 returning to the non-operating position. Since said detachment position R5 is provided downstream of the abutment position R2, when the retaining device 60 detaches itself from the blank 7, the latter is retained on the mandrel 10 in addition to the friction force generated by the movement of the mandrel 10 itself, also by the folding device 20 which has already engaged the blank 7 and which exerts a thrust force on the blank 7 to fold it on the mandrel 10. The blank 7 is therefore interposed between the mandrel 10 and the folding device 20. Thus, the blank 7 does not displace itself from the desired position.

(70) Conveniently, by acting on the actuation element 63, 63, it is possible to vary the duration of the retention, i.e. the distance between the retention position R4 and the detachment position R5, based, for example, on the characteristics of the blank 7. In one embodiment, the retaining device 60 is held in the operating position E1 until the end of the step of forming the box 2.

(71) A very precise folding of the box 2 around the mandrel 10 is obtained.