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(11) | EP 0 650 893 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Device for erecting tubular flattened blanks in a case feeding line |
| (57) A device for erecting tubular flattened blanks (2) in a line (10) for feeding cases
(50) comprises alternative means (20) aimed at withdrawing the blanks (2) from a magazine
(3), a conveying suction belt (4), operated continuously, on which the means (20)
releases each blank (2) that is to be conveyed to the erecting station (40). The station
(40) is designed to open said blank (2), in order to obtain, during a dwell phase
(A) of the line (10), a correspondent case (50) located inside a housing (60) that
is defined onto the running plane (12) of the feeding line (10), and by a pair of
prongs (11). The feeding line (10) is made to advance step by step and in phase relation
with the erecting station (40). |
[0001] The present invention relates to machines for erecting cases and/or boxes, starting from a tubular flattened blank.
[0002] In particular, the present invention refers to a device that takes tubular flattened blanks from a magazine, prints them and conveys them to an erecting station connected with housing provided in a line for feeding the already formed cases.
[0003] For a long time there have been known automatic machines capable of withdrawing tubular flattened blanks from a magazine, of erecting the cases by positively opening the blanks, and then of collocating them onto a conveying line.
[0004] In the US Patent N. 3.783.752 of H.J. Langen & Sons Ltd., Rexdale, Ontario, Canada, a mechanical blank handling device is described.
[0005] This device includes a conveyor equipped with sucker cups aimed at withdrawing the tubular flattened blanks from a magazine and conveying them to an opening station, where the blanks, still flattened, are gripped by special sucker cups, located opposed to the ones of the conveyor and therefore, they are opened due to the progressive moving away of the conveyor sucker cups from the ones of the opening station.
[0007] The main drawback of this device is that it can be used only for blanks of big size and only with relatively low operative speeds.
[0008] Another drawback results from the fact that the blank is opened before being placed between the conveyor prongs.
[0009] Still a further disadvantage arises from the fact that such a device must use special sensors to detect the presence of the blank in order to keep the suckers, that grip the adjacent walls of the same blank, in correct phase relation.
[0010] Another disadvantage results from the fact that the device is not provided with a blank printing station that intervenes on the blanks before they are placed onto the conveyor.
[0011] The main object of the present invention is to propose a device for erecting tubular flattened blanks in a cases feeding line, capable of opening the blanks right between the prongs of the feeding line.
[0012] A further object of the present invention is to propose a device relatively simple to be constructed, safely reliable and capable of operating at high productive speeds as well as allowing for opening blanks of various sizes.
[0014] The characteristic features of the present invention are pointed out in the following with reference to the attached drawings, in which:
- Fig. 1 shows a lateral schematic view of the device being the subject of the present invention, in the phase of withdrawing the flattened blank from the magazine;
- Fig. 2 shows the device of the Fig. 1 in the phase of transporting the flattened blank;
- Figs, 3, 4, 5 and 6 show a lateral view, in enlarged scale, of the opening station of the device of the Fig. 1, respectively in the phases in which: the blank is still flattened, is partially unfolded, is completely open and at the end is transported by the conveyor;
- Fig. 7 shows a lateral schematic view of a second embodiment of the device being the subject of the present invention;
- Figs. 8, 9, 10 and 11 show lateral, enlarged views of the opening station of the device illustrated in Fig. 7, respectively in the phases of flattening and unfolding of the tubular blank, and in the phases of complete opening and transporting of the so formed case;
- Figs. 12, 13, 14 and 15 show lateral enlarged views of a third embodiment of the opening station of the device, respectively in the phases of flattening and unfolding the tubular blank and in the phases of complete opening and transporting the so formed case.
[0015] With reference to the Figures from 1 to 6, the reference number 1 indicates a device for erecting tubular flattened blanks 2, comprising withdrawing means 20, a conveying suction belt 4, an erecting station 40 and a feeding line 10 for the cases 50.
[0016] Each tubular blank 2, when flattened, shows two faces, internal 51 and external 52, respectively, an upper corner 15 and a lower corner 16.
[0017] The faces 51 and 52 of the blank 2 normally have creasings that define, among other things, a bottom wall 2a, an upper wall 2d and lateral walls 2b, 2c, adjacent respectively to the upper corner 15 and the lower corner 16.
[0018] The feeding line 10 is equipped with consecutive couples of prongs 11, each couple including a front prong 11a and a rear prong 11b respectively, which are orthogonal to the running surface 12 of the same line, and which form, together with the surface 12, a housing 60 of a case 50.
[0019] The feeding line moves forward step by step and in phase relation with operation of the erecting station 40.
[0020] The means 20 that withdraws the flattened blanks 2 from a magazine 3, includes an operative unit 21 comprising an articulated parallelogram 29 and an arm 23. One end of the arm 23 is bound to one side of the parallelogram 29.
[0021] The arm 23, provided in its free end with suction gripping means 24 (sucker cups) that grip the flattened blank 2, oscillates alternatively between two extreme positions, that is a position P where the blank 2 is withdrawn, and a position R where the blank is released, respectively.
[0022] When the release phase R is approaching, the parallelogram 29 (in a known, not illustrated way) rotates around its hinge 22, opposite to the arm 23, causing also axial translation of the arm 23 in the advancement direction D of the conveying suction belt 4.
[0023] Such belt is operated continuously and has the task of conveying, by using known and not illustrated suction means, the flattened blanks 2 released on the same belt by the withdrawing means 20 during the release phase.
[0024] The erecting station 40 is positioned near to the terminal end of the belt 4, and includes three operative units 41, 42, 43, respectively first, second and third.
[0025] The first operative unit 41 is constituted by a first lever 49a, hinged at one side to a not illustrated actuator and at the other side to one end of a second lever 49b.
[0026] A first suction gripping means 41a (sucker cup) for gripping each tubular flattened blank 2, is fastened to the other end of the said second lever 49b.
[0027] The first operative unit 41 comprises also a third lever 49c, hinged at one side to the supporting means of the conveying belt 4, and at the other side to the lever 49b, in particular to a part thereof located near to the first gripping means 41a.
[0028] The first operative unit 41 imposes an alternative motion to the first gripping means 41a, that moves between two extreme positions, respectively Q and L. When the first gripping means 41a is in the first position Q, it grips the lateral wall 2c of the flattened blank 2, while when the first gripping means 41a is in the second position L it moves away from the blank 2, after that this latter blank has been opened to form the case 50.
[0029] The second operative unit 42 includes an arm 44, having one end hinged on a pin 45 that is positioned in correspondence to the intersection point of the plane defined by the lowering run 4a of the conveying belt 4, with the running surface 12.
[0031] The second operative unit 42 causes the oscillation of the second gripping means 42a that moves between two extreme positions, respectively V and O. In the first position V the bottom wall 2a of the blank 2 is engaged by the gripping means 42a, while in the second position O the blank 2 is released after having been opened to form the case 50.
[0032] The third operative unit 43 includes an articulated parallelogram and a pusher 43a having one end bound to one side of the same parallelogram.
[0033] The third operative unit 43 has the task of moving alternative the pusher 43a between two extreme positions, respectively I and S. In the first position I the pusher 43a is located outside the housing 60 during the dwell phase A of the feeding line 10, while in the second position S the pusher 43a is located over the open section of the same housing 60 that contains the case 50.
[0034] The task of the pusher 43a is to keep the same case 50 in an open position between the prongs 11a, 11b of the feeding line 10 during the phase Z when the line moves forwards.
[0035] The device 1 is equipped also with means 30 for printing stamping the flattened blanks 2, situated upstream of the erecting station 40. Said printing means 30 comprise a couple of cylinders 31, mounted in tangential relation and rotating in opposed directions.
[0036] Each blank 2, while it is transported by the suction belt 4, passes between the cylinders 31 which perform a printing operation at least one side of the same flattened blank.
[0037] The operation of the device 1 is basically based on the phase relation existing between the various operative phases of the withdrawing means 20, the erecting station 40 and the feeding line 10.
[0038] A complete cycle of opening a flattened blank 2 to form a case 50 is described in the following.
[0039] After that the conveying suction belt 4 has been started up, the withdrawing means 20, by activating the operative unit 21, begins the phase P, in which the sucker cups 24 grip the first blank 2 (considering the loading order in the magazine) on the internal face 51 thereof.
[0040] Subsequent movement of the operative unit 21, mainly guided by cam means, therefore by its arm 23, causes the blank 2 to be brought near the conveying belt 4.
[0041] At this point the release phase R begins, in which the blank is first accelerated in the direction of the belt 4 motion, by the axial translation of the arm 23, so as to reduce practically to zero the relative speed between the belt 4 and the blank.
[0042] Then the sucker cups 24 release the blank 2 that is gripped by the suction belt 4 through known and not illustrated sucking means made in the same belt and kept always active.
[0043] Therefore, the belt 4 conveys the blank 2 that passes between the printing means 30 which print or not, depending on their arrangement, the internal face 51 and/or the external face 52 of the blank 2.
[0044] While the blank 2 is conveyed by the belt 4, the feeding line 10 passes from the dwell phase A to the advancement phase Z, at the end of which, i.e. in correspondence with a new stop phase A, the internal wall 13 of the front prong 11a is coplanar with the lowering run 4a of the belt 4.
[0045] Therefore, the blank 2 reaches the terminal end of the belt 4 and, as illustrated in the Figure 3, passes between the sucker cup 41a (at the beginning of the position Q) and the sucker cup 42a (at the beginning of the position V), placing its lower corner 16 in correspondence with the axis of the pin 45.
[0046] The internal face 51 rests on the internal wall 13 of the prong 11a. In that moment, the sucker cups 41a and 42a are activated so as to grip respectively the lateral wall 2c and the bottom wall 2a of the blank 2.
[0047] The first operative unit 41 remains in the position Q while the second operative unit 42 moves the arm 44 so as to progressively unfold the blank 2, until it is completely open to form the case 50 in correspondence with an intermediate position E (illustrated in Figure 5).
[0048] In the position E, the bottom wall 2a of the same blank is brought to contact the running surface 12 of the line 10 while the lateral wall 2b adheres to the internal wall 14 of the rear prong 11b.
[0049] When such intermediate position E is left, the first operative unit passes to the position L and the second operative unit passes to the position O.
[0050] The feeding line 10 moves forward by one step on the basis on the activation of the phase Z, at the end of which the operative unit 43 passes from the position S to the position I.
[0052] Fixed strikers, known and not illustrated, are provided downstream of the pusher 43a, and perform the same function as this latter.
[0053] With reference to the Figures from 7 to 11, a second embodiment of the erecting station 40 of the device 1, subject of the present invention, will be described in the following.
[0054] Such erecting station 40 includes a frame 70, a first actuator 76 and a second actuator 75 (cylinder).
[0055] The frame 70 includes a base 71 situated below the feeding line 10 and arranged parallel thereto.
[0056] A support 72, made integral with the base 71 and arranged perpendicular thereto, extends upwardly beyond the line 10 through a portion longer than the height of the blank 2.
[0057] A pusher 74 is attached to the free end of the support 72, overhanging the base 71 and arranged parallel thereto. The pusher 74 is not longer than the base 71.
[0058] The base 71 features a slope 73 attached to the its free end and having a sloping surface 73 turned outwards with respect to the frame 70 and designed to guide the blank 2 during the unfolding phase W of the same blank.
[0059] The first actuator 76 is bound to the support 72, and perpendicular thereto, near the pusher 74, and it supports a gripping means 77 for gripping the blank 2.
[0060] Said gripping means 77 is designed to be moved alternatively by the first actuator 76 from a first extreme position H, wherein the distance between the gripping means 77 and the support 72 is maximum, to a second intermediate position K, in which the means 77 are nearer to the support 72, and to a third extreme position J, in which the gripping means 77 are the nearest to the support 72.
[0061] The position H is relative to the gripping phase, i.e. when the blank 2 is gripped by the gripping means 77, while the intermediate position K corresponds to the unfolding phase W of the same blank, and finally, the phase J is relative to a releasing phase F of the case 50.
[0062] The gripping means 77 includes a sucker cup 78 supported by a stem 79 having the minimum and maximum strokes corresponding respectively to a position C, in which the distance between said sucker cup 78 and the blank is the biggest, and to a position B, in which the sucker cup 78 is the nearest to the same blank.
[0063] The second actuator 75 (cylinder) is bound to the base 71 and is designed to move alternatively the frame 70, in direction orthogonal to the feeding line 10, between two extreme positions, respectively a raised position X and a lowered position Y, respectively set in phase relation with the dwell phase A and the advancement phase Z of the same feeding line, so as to delimit, correspondingly, the maximum and minimum protruding of the support 72 with respect to the feeding line 10.
[0064] As far as the operation of the device 1 in the second embodiment is concerned, there are not changes in the phases order according to which the blank 2 is withdrawn from the magazine 3 and conveyed by the belt 4, through the printing means 30, until the erection station 40, i.e. until the internal face 51 rests on the internal wall 13 of the prong 11a, while its lower corner 16 is fitted in between the internal wall 13 and the slope 73, as it is shown in Figure 8.
[0065] The cylinder 75 is shifted to the position X and the first actuator 76 to the position K before the blank 2 reaches the erection station 40.
[0066] When the blank 2 has reached the erection station 40, the actuator 76 passes from the position K to the position H so that the gripping means 77, passing from the position C to the position B, grips the lateral wall 2b of the blank 2.
[0067] At this point, with reference to Figure 9, the gripping means 77 returns to the position C and, at the same time, the first actuator 76, returning to the position K, causes the unfolding of the blank 2 both because the lower corner 16 and the bottom wall 2a of the blank slide over the sloping surface 73a of the slope 73, and because the upper corner 15 of the blank slides against the wall of the pusher 74 that faces the base 71.
[0068] As illustrated in Figure 10, the complete opening of the blank 2 takes place during the passage of the frame 70 from the position X to the position Y, so as to obtain a correspondent case 50.
[0069] When the frame 70 has passed from the position X to the position Y, the gripping means 77 releases the face 52 and the first actuator 76 passes from the position K to the position J, while the case 50 is kept inside the housing 60 by the pusher 74, as it results from the Figure 11.
[0070] The feeding line 10 is made to pass from the phase A to the phase Z while the frame 70 is shifted from the position Y to the position X, in order to start again a new erecting cycle for a subsequent tubular flattened blank.
[0071] With reference to the Figures from 12 to 15, a third embodiment of the erecting station 40 is described in the following.
[0072] The erecting station 40 includes a frame 170 and an operative unit 80. The frame 170 includes a base 171 situated below the feeding line 10 and arranged parallel thereto.
[0073] A support 172, made integral with the base 171 and arranged perpendicular thereto, extends upwardly beyond the line 10 through a portion that is not lower than the height of the blank 2.
[0074] A striker 174 is attached to the free end of the support 172, overhanging the base 171 and arranged parallel thereto.
[0075] A protrusion 175, attached orthogonally to the same feeding line 10, is turned toward the base 171 and oriented so as to have the internal surface 175a, with reference to the housing 60, coplanar with the internal surface 14 of the said rear prong 11b, during the dwell phase A of the feeding line 10.
[0076] Known and not illustrated means move alternatively the frame 170 in direction orthogonal to the feeding line 10, between two extreme positions, respectively a raised position X, illustrated in Figure 12, and a lowered position Y, shown in Figure 14.
[0077] These extreme positions X and Y, which are made to occur respectively in phase relation with the dwell phase A and the advancement phase Z of the feeding line 10, define, correspondingly, the maximum and minimum protrusion of the cited support 172 with respect to the feeding line 10.
[0078] The operative unit 80 includes an arm 81 having one end hinged below the running plane 12, near to the front prong 11a, and the other end equipped with gripping means 82 (sucker cup) turned upwards.
[0079] The operative unit 80 oscillates between two extreme positions, respectively a first position M and a second position T.
[0080] In the first position M, the arm 81 is vertical or inclined in upstream direction with respect to the advancement direction of the feeding line 10: in such a situation, the length of the part of said arm comprised between the running plane 12 and the sucker cup 82 must be smaller than the longitudinal extension of the bottom wall 2a of the blank 2.
[0081] Also in the first position M, that occurs in synchrony with the dwell phase A of the feeding line 10, the sucker cup 82 first supports and subsequently grips, when activated, the bottom wall 2a of the blank.
[0082] In the second position T such arm 81 is directed upwards and situated below the running plane 12.
[0083] As far as the operation of the device 1 in the third embodiment is concerned, there are not changes in the order of the phases in which the blank 2 is withdrawn from the magazine 3 and conveyed by the belt 4, through the printing means 30, until the erection station 40, i.e. until the internal face 51 rests on the internal wall 13 of the prong 11a, while its lower corner 16 is fitted in between the internal wall 13 and the arm 81 located in the position M, as it is shown in Figure 12.
[0084] Before the blank 2 has reached the erecting station 40, the frame 170 is moved to the position X, the operative unit 80 is moved to the position M and the feeding line 10 is set in the phase A.
[0085] After the blank has reached the erecting station, it rests on the sucker cup 82 performing a movement, indicated with the arrow D in the figure 12, due to both its kinetic energy, and to the fact that the lowering run 4a of the belt 4 is no longer sucking and also because the lower corner 16 is constrained between the prong 11a and the arm 81.
[0086] At this point, the sucker cup 82 is activated and the operative unit 80 grips the bottom wall 32a of the blank 2, and, with reference to the Figure 13, the blank unfolding phase W is activated, in which the frame 170 passes progressively from the position X to the position Y and the operative unit 80 passes from the position M to the position T.
[0087] The blank 2 is unfolded because of the initial sliding of the upper corner 15 of the same blank 2 on the internal wall 175a of the protrusion 175 or on the wall of the striker 174, until it definitely fits in the angle between the protrusion 175 and the striker 174.
[0088] Therefore, the operative unit 80 passes to an intermediate position N, shown in the Figure 14.
[0089] In this position, the sucker cup 82, previously deactivated, detaches and progressively moves away from the bottom wall 2a of the blank 2 until it reaches the second position T in which the same sucker cup is below the feeding line 10.
[0090] As illustrated in Figure 15, the complete opening of the blank 2 so as to obtain a correspondent case 50, takes place during the passage of the operative unit from the position N to the position T, activated by the ultimate part of lowering of the frame 170, in cooperation with the walls of the housing 60, inside which the case 50 is kept by the pressure of the striker 174 on the upper wall 2d of the blank 2.
[0091] The feeding line 10 is made to pass from the phase A to the phase Z and the frame 170 is shifted from the position Y to the position X in order to start again a new erecting cycle for a subsequent tubular flattened blank, while the case 50, just formed, is kept inside the housing 60 by a fixed stop 176 situated downstream of the frame 170, at the same height reached by the striker 174 when the frame 170 is in position Y.
- means (20) for withdrawing flattened blanks (2) from a magazine (3), including an operative unit (21) that supports an arm (23) equipped at its end with gripping means (24) and oscillating alternatively between two extreme positions, respectively a position (P) wherein the above mentioned blank (2) is gripped, and a position (R) wherein the said blank (2) is released, with said operative unit (21) capable of translating axially said arm (23) during the said release phase (R);
- a conveying suction belt (4), operated continuously and designed to convey flattened blanks (2) released on the same belt by the withdrawing means (20) during the release phase (R);
- an erecting station (40) positioned near one end of the cited belt (4) and designed to grip each cited blank (2), conveyed by the belt (4), and to erect it so as to obtain the correspondent case (50) located inside the above mentioned housing (60) during a dwell phase (A) of the cited feeding line (10) that is moved in phase relation with the operation of said station (40).
- a first operative unit (41), constituted by a series of levers, hinged one to another, one of these levers having, attached at one end, at least one first gripping means (41a) designed to grip each tubular flattened blank (2), said first operative unit (41) being able to carry the said first gripping means through an alternative motion between two extreme positions, respectively a first position Q in which the lateral wall (2c) of the flattened blank (2) is withdrawn by the said first gripping means (41a), and a second position (L) in which the first gripping means (41a) are moved away from the said blank (2), after that the blank has been opened to form the above mentioned case (50);
- a second operative unit (42) that includes at least one arm (44) having one end hinged to intersection point of the said front prong (11a) and the running surface (12), and having the other end provided with second suction gripping means (42a), with said second operative unit (42) bringing the said cited second gripping means (42a) through an oscillating motion between two extreme positions, respectively a first position (V) in which the bottom wall (2a) of the cited blank (2) is gripped by the said gripping means (42a), and a second position (O) in which the said blank (2), shaped to form the said case (50), is released between the above mentioned prongs (11);
- an a third operative unit (43), that includes a parallelogram with at least one pusher (43a) bound thereto, so that the pusher (43a) is caused to reciprocate alternatively between two extreme positions, respectively a first position (I), in which the pusher (43a) does not insert into the said housing (60) during the cited dwell phase (A) of the feeding line (10), and a second position (S) in which the said pusher (43a) is placed over the open part of the same housing (60) containing the cited case (50), with said pusher (43a) designed to keep the said case in the open position inside the prongs (11a,11b) of the feeding line (10) during its advancement phase (Z).
- a frame (70), including a base (71) situated below the said feeding line (10), a support (72), made integral with the base (71) and extending upwardly beyond the line (10) through a portion that is not shorter than the height of the blank (2), and a pusher (74) that is attached to the free end of the support (72), overhanging the base (71) and arranged parallel thereto, with said base (71) featuring a slope (73) attached to its free end and designed to guide the blank (2) during the unfolding phase (W) of the same blank;
- a first actuator (76) orthogonally bound to the support (72) near the said pusher (74) and supporting at least one gripping means (77) designed to grip the said blank (2), said gripping means (77) being moved alternatively by the said first actuator (76) from a first extreme position (H), wherein the distance between said gripping means (77) and the said support (72) is maximum, to a second intermediate position (K), in which the said means (77) are nearer to the said support (72), and to a third extreme position (J), in which the said means (77) are the nearest to the said support (72), with said first extreme position (H) being relative to the gripping phase of the said blank (2) by said gripping means (77), and with said second intermediate position (K) corresponding to the unfolding phase (W) of the same blank, and with said third position (J) being relative to a releasing phase (F) of the said case (50);
- and a second actuator (75), bound to the said base (71) and designed to move said frame (70), in direction orthogonal to the said feeding line (10), between two extreme positions, respectively a raised position (X), set in phase relation with the dwell phase (A) of the said feeding line (10), and lowered (Y), set in phase relation with the advancement phase (Z) of the same feeding line, so as to delimit, correspondingly, the maximum and minimum protruding of the said support (72) with respect to the feeding line (10), the lowering of the said frame (70), activated in phase relation with the passage of the said first actuator (76) from the said first position (H) to the third position (K), causing first the unfolding of the said blank (2), due to the sliding and guiding action of the said slope (73) onto the said bottom wall (2a) of the blank (2), and then the opening of the blank (2) inside the said housing (60) to form a case (50) therein.
- a frame (170), including a base (171) situated below the said feeding line (10), a support (172), made integral with the base (171) and extending upwardly beyond the line (10) through a portion that is not shorter than the height of the blank (2), a striker (174) that is. attached to the free end of the support (172), overhanging the base (171) and arranged parallel thereto, and a protrusion (175), attached orthogonally to said striker (174), turned downwards and oriented so as to have its internal surface (175a) coplanar with the internal surface (14) of the said rear prong (11b), during the dwell phase (A) of the feeding line (10), with said frame (170) being moved alternatively in direction orthogonal to the feeding line (10), between two extreme positions, respectively a raised position (X), set in phase relation with the dwell phase (A), and a lowered position (Y), set in phase relation the advancement phase (Z) of the feeding line (10), so as to define, correspondingly, the maximum and minimum protrusion of the said support (172) with respect to the feeding line (10);
- an operative unit (80), including at least one arm (81) hinged at its lower part to a point below the said running plane (12) near the said front prong (11a), and equipped with at least one gripping means (82) turned upwards, with said unit oscillating between a first extreme position first (M), in which such arm (81) is vertical or inclined in upstream direction with respect to the advancement direction of the feeding line (10), so that the length of the part of said arm calculated from said running plane (12) to the said gripping means (82) is shorter than the longitudinal extension of the said bottom wall (2a) of the blank (2), and a second extreme position (T), in which said arm (81) is directed upwards and situated below the said running plane (12), with the said first position (M) set in synchrony with the dwell phase (A) of the feeding line (10), and designed to allow said gripping means (82) to firstly support and subsequently grip, due to the activation of the same gripping means, the bottom wall (2a) of the blank, while the lowering of the said frame (170), activated in phase relation with the passage of the operating unit (80) from the first (M) to the second extreme position (T), first causes the unfolding of the blank (2), because of the pushing and guiding action performed by the said protrusion (175) and by the above mentioned striker (174) on the upper corner (15). of the blank (2), and then the subsequent partial opening of the blank (2) until deactivation of the said gripping means (82), carried out in correspondence with a position (N) of the said operative unit (8), intermediate with respect to the said extreme positions (M,T), and subsequently the opening of the blank is completed in the said housing (60), with cooperation with the walls defining the latter.