Patent Publication Number: US-11642863-B2

Title: Folding unit and method for forming an empty cardboard box by folding a blank around a mandrel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is the U.S. national phase of International Application No. PCT/IB2018/057071, filed Sep. 14, 2018, which claims the benefit of Italian Patent Application No. 102017000103228, filed Sep. 18, 2017. 
     TECHNICAL FIELD 
     The present invention relates to a folding unit and method for forming an empty cardboard box. 
     The present invention finds advantageous application in forming an empty cardboard box in a packaging machine which produces packets for non-combustible cigarettes, i.e. for the so-called HNB (“Heat Not Burn”) cigarettes, which the present invention will make explicit reference without losing generality 
     PRIOR ART 
     Recently the new generation cigarettes have been proposed on the market, i.e. the non-combustible cigarettes (HNB cigarettes) in which the tobacco is electrically heated in order to obtain the sublimation of the aromatic substances contained in the tobacco itself. 
     For the marketing of the new generation cigarettes, a package formed by a cardboard box containing a group of heterogeneous articles (i.e. of a different type) comprising an electronic cigarette, a set of single-use cartridges (i.e. disposable) for the electronic cigarette, and one printed sheet (containing the use and warning instructions). 
     For the production of the package above described, the use of a packaging machine comprising a formation unit has been proposed, in which the group of heterogeneous articles is manufactured, a folding unit, in which the empty cardboard box is manufactured, an insertion unit, in which the group of heterogeneous articles is inserted inside the cardboard box, and a closing unit, in which the open ends of the cardboard box are closed to complete the manufacturing of the package. 
     According to a first embodiment, the cardboard boxes are fed, already formed and flattened, to the folding unit and consequently, in the folding unit, each already formed cardboard box is simply erected by rotating two opposite side walls by 90° in respect to the lower and upper base walls; however, this embodiment requires a further packaging machine which forms the cardboard boxes upstream of the folding unit and thus increases the cost and the complexity of the plant. 
     According to an alternative embodiment, flat blanks are fed to the folding unit, which are folded into a tubular shape and stabilized by means of glue in the folding unit; however, this embodiment presents a low productivity (i.e. the number of pieces that can be produced in an hourly unit) which can be significantly increased only at the expense of the final quality of the cardboard box. 
     The U.S. Pat. No. 2,209,110A describes a packaging machine provided with a mandrel around which a sheet of wrapping material is folded to manufacture a package; the mandrel comprises two parts which are mobile in respect to one another between an expanded configuration, in which the two parts are further from one another to confer a maximum size to the mandrel, and a contracted configuration, in which the two parts are closer to one another to confer a minimum size to the mandrel. 
     Patent application WO9616789A1 describes an adjustable-size mandrel fitted in a drum of a packaging machine; the size of the mandrel can be reduced so as to allow an easier removal of the package from the mandrel at the end of the folding and also to perform a quicker format change, which involves the variation in the size of the package. 
     U.S. Pat. No. 3,530,773A describes a formation mandrel around which a sheet of wrapping material is folded to manufacture a package; the mandrel comprises two parts which are mobile in respect to one another between an expanded configuration, in which the two parts are further from one another to confer a maximum size to the mandrel, and a contracted configuration, in which the two parts are closer to one another to confer a minimum size to the mandrel. 
     DESCRIPTION OF THE INVENTION 
     The object of the present invention is to provide a folding unit and method for forming an empty cardboard box, which unit and folding method allow to achieve high productivity and are, at the same time, easy and inexpensive to manufacture. 
     According to the present invention, a folding unit and method are provided for forming an empty cardboard box, as claimed in the appended claims. 
     The claims describe preferred embodiments of the present invention forming an integral part of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting example of embodiment, wherein: 
         FIG.  1    is a perspective view of a package for a HNB electronic cigarette; 
         FIG.  2    is a perspective view of a heterogeneous group of articles contained in the package of  FIG.  1   ; 
         FIG.  3    is a plan view of a blank which is folded and glued so as to manufacture a cardboard box of the package of  FIG.  1   ; 
         FIG.  4    is a front view and with the removal of parts for clarity of a packaging machine that manufacture the package of  FIG.  1   ; 
         FIG.  5    is a front view and with the removal of parts for clarity of a formation unit of the packaging machine of  FIG.  4   ; 
         FIGS.  6  and  7    are two different perspective views of a tray of the formation unit of  FIG.  5   ; 
         FIG.  8    is a front view of the tray of  FIGS.  6  and  7   ; 
         FIG.  9    is a front view and with the removal of parts for clarity of a folding unit of the packaging machine of  FIG.  4   ; 
         FIG.  10    is a front view and with the removal of parts for clarity of a folding drum of the folding unit of  FIG.  9   ; 
         FIG.  11    is a perspective view of the folding head of a folding drum of  FIG.  10   ; 
         FIG.  12    is a front view of the folding head of  FIG.  11   ; 
         FIGS.  13  and  14    are two front and schematic views of a mandrel of the folding head of  FIG.  11    in an expanded configuration and in a contracted configuration, respectively; and 
         FIG.  15    is a schematic plan view of an inserting unit of the packaging machine of  FIG.  4   . 
     
    
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     In  FIG.  1   , number  1  denotes as a whole a package for a HNB electronic cigarette. 
     The package  1  comprises a cardboard box  2  made of cardboard (or other similar material) with a parallelepiped shape inside which a group  3  of heterogeneous articles (i.e. of different types) is contained, which is illustrated in  FIG.  2   . 
     In the non-limiting embodiment illustrated in  FIG.  2   , the group  3  of heterogeneous articles comprises an electronic cigarette  4 , a set  5  of single-use cartridges (i.e. disposable) for the electronic cigarette  4  and a printed sheet  6  (containing the use and warning instructions and folded in an “accordion-like” manner). 
     The set  5  of disposable cartridges comprises a rigid or semi-rigid base  7  which has an extension equal to the width of the package  1  (so as to be contained in the package  1  without clearance and therefore not “shaking” inside the package  1 ) and a casing  8  (schematically illustrated in  FIG.  2   ) which rises from the base  7  and houses the disposable cartridges; according to a possible embodiment, the set  5  is manufactured as a blister pack and therefore the casing  8  has several transparent plastic chambers closed at the bottom by an aluminium sheet. 
     The cardboard box  2  is manufactured by folding and stabilizing by means of gluing a blank  9  of cardboard illustrated in  FIG.  3   . 
     The blank  9  comprises two pre-weakened transversal folding lines  10  and four pre-weakened longitudinal folding lines which define, between the pre-weakened transverse folding lines  10 , a connecting tab  12  and four panels  13 - 16  which form four corresponding side walls of the cardboard box  2 . Each panel  13 - 16  has a pair of corresponding fins  17 , which are arranged on opposite sides of the panel  13 - 16 , are separated from the panel  13 - 16  by the two pre-weakened transversal folding lines  10 , and are folded so as to form two end walls of the cardboard box  2 . 
     During forming the cardboard box  2 , the connecting tab  12  is glued (i.e. provided with glue) so as to stabilize the tubular shape of the cardboard box  2  by permanently adhering the connecting tab  12  to an inner surface of the panel  16 . During the closing of the open ends of the cardboard box  2 , the fins  17  of the panel  13  are glued (i.e. provided with glued) so as to stabilize the two end walls by permanently adhering each fin  17  of the panel  13  to the underlying fin  17  of the panel  16 . 
     In  FIG.  4    number  18  denotes as a whole a packaging machine that manufactures the package  1  described above by forming the group  3  of articles, by forming the empty cardboard box  2  (i.e. without contents), by inserting the group  3  of articles into the cardboard box  2 , and finally by closing the ends of the cardboard box  2 . 
     According to a preferred but non-binding embodiment, the packaging machine  18  operates with a continuous motion, i.e. the main conveyors of the packaging machine  18  advance with a constant speed devoid of stops. Alternatively, the packaging machine  18  could operate intermittently, i.e. the main conveyors of the packaging machine  18  advance by cyclically alternating a motion step and a still step. 
     The packaging machine  18  comprises a formation unit  19 , in which the group  3  of heterogeneous articles is formed, a folding unit  20 , in which the empty cardboard box  2  is manufactured (by leaving the two opposite ends of the cardboard box  2  open), one insertion unit  21 , in which the group  3  of heterogeneous articles is longitudinally inserted into the cardboard box  2  previously manufactured, and a closing unit  22 , in which the open ends of the cardboard box  2  are closed (by folding and overlapping the fins  17 ) in order to complete the manufacturing of the package  1 . 
     As illustrated in  FIG.  5   , the formation unit  19  comprises a formation conveyor  23  which feeds a series of formation pockets  24  along a rectilinear and horizontal formation path P 1 ; preferably, the formation conveyor  23  comprises (at least) a flexible belt which is closed in a loop around two end pulleys (at least one of which is motorized) and supports the formation pockets  24 . 
     The formation unit  19  comprises a feeding device  25  which is arranged along the formation path P 1  and inserts a corresponding mould  6  into each formation pocket  24 , a feeding device  26  which is arranged along the formation path P 1 , downstream of the feeding device  25  and inserts a corresponding electronic cigarette  4  into each formation pocket  24 , and a feeding device  27  which is arranged along the formation path P 1  downstream of the feeding device  26  and inserts a corresponding group  3  of articles into each formation pocket  24 . 
     Each feeding device  25 ,  26  or  27  comprises its own feeding conveyor which is arranged next to the formation conveyor  23  and has a series of feeding pockets which, for a given section, are fed parallel and in a synchronous manner to the formation pockets  24 . In use each feeding pocket of a feeding conveyor receives a corresponding article (an electronic cigarette  4 , a set of cartridges  5 , or a printed sheet  6 ) in a first area of its path and while the feeding conveyor is still. Furthermore, in use each feeding pocket of a feeding conveyor releases a corresponding article (an electronic cigarette  4 , a set of cartridges  5  or a printed sheet  6 ) in a second area of its path and while the feeding conveyor is moving so as to feed the feeding pocket synchronously with a forming pocket  24 ; the transfer of an article (an electronic cigarette  4 , a set  5  of cartridges or a printed sheet  6 ) from a feeding pocket to a forming pocket  24  takes place by means of a pusher which synchronously moves with the same pockets and performs a push stroke perpendicular to the forming P 1  path. 
     When the packaging machine  18  operates with a continuous motion, the formation conveyor  23  has a constant speed devoid of stops whereas the feeding conveyor of the feeding devices  25 ,  26  and  27  can have an intermittent motion which cyclically alternates the still steps (in which the articles are inserted into the feeding pockets) and the motion steps (in which the articles are transferred from the feeding pockets to the corresponding forming pockets  24 ). 
     According to a different embodiment, the two feeding devices  26  and  27  are integrated to one another to initially combine an electronic cigarette  4 , a set  5  of cartridges on the outside of the formation conveyor  23  and therefore to feed together the electronic cigarette  4  and the set  5  of cartridges to a formation pocket  24  of the formation conveyor  23 . 
     As illustrated in  FIGS.  6 ,  7  and  8   , each formation pocket  24  comprises a base wall  28  which is rigidly fixed to the formation conveyor  23  by means of a pair of screws (in  FIGS.  6  and  7    the two through holes, through which the screws pass, are shown); from the base wall  28  of each formation pocket  24  two opposite side walls  29  rise, which laterally contain the group  3  of articles. Inside each formation pocket  24  a seat  30  is obtained, which is shaped to house an electronic cigarette  4 , a seat  31  shaped to house a set  5  of cartridges, and a seat  32  shaped to house a mould  6 . In particular, in each formation pocket  24  an appendix  33  is provided, which rises in a cantilever fashion from a side wall  29  and defines the seat  30  shaped to house an electronic cigarette  4 ; under the appendix  33  a space for housing one end of the base  7  of a set  5  of cartridges is provided. 
     According to a preferred, non-binding embodiment, illustrated in  FIG.  6   , the base wall  28  of each formation pocket  24  has a chute (i.e. an inclined plane that confers a progressively increasing thickness to the base wall  28 ) which is arranged on the side of the formation pocket  24  where the set  5  of cartridges is inserted. 
     As illustrated in  FIGS.  9  and  10   , the folding unit  20  comprises a folding drum  34  which is vertically arranged, is mounted rotatable about a horizontal rotation axis  35  and is adapted to rotate with a continuous motion (i.e. with a constant speed) around the rotation axis  35  (counter clockwise as illustrated in  FIGS.  9  and  10   ) for cyclically advancing along a circular folding path P 2 . The folding drum  34  supports a plurality of folding heads  36 , each of which is provided with a mandrel  37  with a parallelepiped shape around which a corresponding blank  9  is folded into a tubular shape (i.e. so as to assume a tubular shape) to form an empty cardboard box  2 ; in other words, each mandrel  37  is adapted to receive a corresponding blank  9  which is folded with a tubular shape (i.e. so as to assume a tubular shape) to form (along the folding path P 2 ) an empty cardboard box  2 . 
     The folding unit  20  further comprises a storage unit  38  which is arranged close to the folding drum  34  and houses a pile of blanks  9  and a feeding drum  39  which is arranged between the storage unit  38  and the folding drum  34  to extract the blanks  9  from an outlet mouth of the storage unit  38  and feed the blanks  9  in succession to the mandrels  37  of the corresponding folding heads  36 . The feeding drum  39  is arranged vertically, is mounted rotatable about a horizontal rotation axis  40  (and parallel to the rotation axis  36 ) and is adapted to rotate with a continuous motion (i.e. with a constant speed) around the rotation axis  40  to cyclically advance along a circular feeding path P 3 . The feeding drum  39  supports a group of sucking holding heads  41 , each of which is adapted to hold a corresponding blank  9  during the transfer of the blank  9  from the outlet mouth of the storage unit  38  to the mandrel  37  of a corresponding folding head  36 . 
     The movement of the feeding drum  39  cyclically moves each holding head  41  between a pickup station S 1  (where the feeding path P 3  begins) in which the holding head  41  picks up a blank  9  from the outlet mouth of the storage unit  38  and a feeding station S 2  (where feeding path P 3  ends) in which the holding head  41  lays the flat blank  9  on a major (i.e. larger) wall of the mandrel  37  of the corresponding folding head  36 ; each flat blank  9  (as illustrated in  FIG.  3   ) is coupled to the mandrel  37  of the corresponding folding head  36  by laying the panel  15  (or, alternatively, the panel  13 ) of the blank  9  to a major (i.e. larger) wall of the mandrel  37 . According to a preferred but not limiting embodiment, each mandrel  37  holds the corresponding blank  9  by suction, i.e. the major wall of the mandrel  37  on which the panel  15  is laid (or, alternatively, the panel  13 ) of the blank  9  has a series of holes which can be connected to a suction source. 
     In the embodiment illustrated in the accompanying figures, in the feeding station S 2  each blank  9  is laid flat on the mandrel  37  of the corresponding folding head  36 . According to an alternative not illustrated, each blank  9  is folded into a “U” or “L” shape on the mandrel  37  of the corresponding folding head  36 ; this “U” or “L” folding of the blank  9  can be carried out before placing the blank  9  on the mandrel  37  or simultaneously while laying the blank  9  on the mandrel  37 . 
     In the preferred embodiment illustrated in the accompanying figures, each holding head  41  is hinged to the feeding drum  39  so as to rotate (due to a camming system) relative to the feeding drum  39  around a rotation axis  42  which it is parallel and spaced apart from the rotation axis  40 ; the relative movement between each holding head  41  and the feeding drum  39  is performed so as to cause the holding head  41  to have a particular orientation in the moments in which the holding head  41  receives or releases the corresponding blank  9 . In the pickup station S 1 , each holding head  41  is rotated around the rotation axis  42  initially in advance and thereafter delayed with respect to the rotation of the feeding drum  39  for coupling the holding head  41  to the outlet mouth of the storage unit  38 . Similarly, in the feeding station S 2 , each holding head  41  is rotated around the rotation axis initially in advance and subsequently delayed with respect to the rotation of the feeding drum  39  for coupling the holding head  41  with the corresponding folding head  36  of the folding drum  34 . 
     The movement of the folding drum  34  cyclically moves each folding head  36  between the feeding station S 2  (where the folding path P 2  starts), in which the folding head  36  receives a blank  9  from a corresponding holding head  39  and a transfer station S 3  (where the folding path P 2  ends), in which the folding head  36  releases an empty cardboard box  2  (obtained by folding the blank  9 ) to the insertion unit  21 . 
     In the preferred embodiment illustrated in the accompanying figures, each folding head  36  is hinged to the folding drum  34  so as to rotate (by a cam actuating system) relative to the folding drum  34  around a rotation axis  43  which it is parallel and spaced apart from the rotation axis  35 ; the relative movement between each folding head  36  and the folding drum  34  cause the folding head  36  to have a particular orientation in the moments in which the folding head  36  receives the corresponding blank  9  and releases the corresponding empty cardboard box  2 . In the feeding station S 2 , each folding head  36  is rotated around the rotation axis  43  initially in advance and subsequently delayed with respect to the rotation of the folding drum  34  so as to couple the folding head  36  with the corresponding holding head  41  of the feeding drum  39 . Similarly, in the transfer station S 3 , each folding head is rotated around the rotation axis  43  initially in advance and subsequently delayed with respect to the rotation of the folding drum  34  so as to couple the folding head  36  with a refining conveyor  44  of the insertion unit  21  (described in the following). 
     The folding unit  20  comprises a gluing device  25 , which is arranged near the folding drum  34  and along the folding path P 2  for applying glue (preferably hot, i.e. preferably quick-setting) to the outer surface of the connecting tab  6  of each blank  9  (during the subsequent folding of the blank  9 , the outer surface of the connecting tab  6  will overlap the inner surface of the panel  10  so as to cause a permanent gluing between the connecting tab  6  and the panel  10 ). In the embodiment schematically illustrated in  FIGS.  9  and  10   , the gluing device  45  is of the spray type, i.e. it comprises one or more glue guns which are activated to supply a pressurized glue spray towards the connecting tab  6  of each blank  9 . 
     The folding unit  13  comprises a series of folding devices (per se of known type) which are arranged near the folding drum  34  and along the folding path P 2  for folding each blank  9  into a tubular shape, around the corresponding mandrel  37 , i.e. to wrap each blank  9  having a tubular shape around the corresponding mandrel  37 . 
     As better illustrated in  FIGS.  11  and  12   , each folding head  36  comprises a support body  46  which is hinged to the folding drum  34  so as to rotate around the corresponding rotation axis  43 . In each folding head  36  the body  46  bears the mandrel  37  which is mounted on the support body so as to axially slide along an axial translational direction, i.e. parallel to the rotation axis  43 , between a work position (illustrated for example in  FIGS.  11  and  12   ), in which the mandrel  37  completely protrudes in a cantilever fashion from the folding head  36  (i.e. it is completely external to the folding head  36 ) and a release position, in which the mandrel  37  moves backwards from the work position (returning towards the folding head  36  and towards the folding drum  34 ) of a stroke (slightly) greater than the axial extension of the empty cardboard box  2 . In this way, by moving from the work position to the transfer position each mandrel  37  can be axially and completely unravelled from the corresponding empty cardboard box  2  that has just been formed. Along the folding path P 2 , the mandrels  37  assume the work position everywhere except in the transfer station S 3  and the mandrels  37  assume the release position only in the transfer station S 3  (according to methods better described in the following). The displacement of the mandrels  37  between the work position and the displacement position and along the translation direction is preferably, but not necessarily, controlled by a cam actuating system which is set into motion by the rotation of the folding drum  34  around the rotation axis  35 . 
     Each folding head  36  further comprises two locking elements  47 , which are arranged on opposite sides of the mandrel  37  (i.e. they enclose the mandrel  37  between one another) and are hinged to the support body  46  so as to rotate, relative to the support body  46 , between a locking position (illustrated in  FIGS.  11  and  12   ), in which each locking element  47  is pressed against a corresponding side wall of the mandrel  37 , and a release position, in which each locking element  47  is relatively far from a corresponding side wall of the mandrel  37 . Along the folding path P 2 , the two locking elements  47  of each folding head  36  assume the release position at the feeding station S 2  so as to allow to fold the blank  9  around the folding mandrel  37 , downstream of the feeding station S 2  in which the blank  9  is laying flat on the mandrel  37 ; as soon as the blank  9  has been folded around a side wall of the mandrel  37 , the corresponding locking element  47  is moved into the locking position to prevent unwanted movements of the blank  9  relative to the mandrel  37  and to apply in the glued areas of the blank.  9  (i.e. provided with glue, therefore to the panel  16  overlapping the connecting tab  12 ) a high pressure which allow an optimal gluing. Finally, along the folding path P 2 , the two locking elements  47  of each folding head  36  assumes the release position at the transfer station S 3  so as to allow the empty cardboard box  2  to be axially extracted from the mandrel  37 . 
     It is important to note that in each folding head  36  the two locking elements  47  have independent movements, i.e. a locking element  47  can rotate around the rotation axis  48  between the locking position and the release position in a completely independent manner from the other locking element  47 . 
     In the preferred embodiment illustrated in the accompanying figures, each folding head  36  comprises two locking elements  47 . According to an alternative not illustrated, each folding head  36  comprises a single locking element  47  arranged at the glued areas of the blank  9  (i.e. provided with glue, therefore the panel  16  overlapping the connecting tab  12 ). According to a further alternative not illustrated, each folding head  36  is completely devoid of the locking elements  47 . 
     According to what is better illustrated in  FIGS.  13  and  14   , each mandrel  37  comprises a fixed part  49  and a movable part  50  which is mounted in a sliding manner relative to the fixed part  49  to translate between an expanded configuration (illustrated in  FIG.  13   ), in which the mobile part  50  it is further from the fixed part  49  thus conferring a greater size to the mandrel  37  (i.e. a larger cross section, i.e. maximum) and a contracted configuration (illustrated in  FIG.  14   ), in which the movable part  50  is closer from the fixed part  49  thus conferring a minor size to the mandrel  37  (i.e. a smaller cross section, i.e. minimum). In other words, the movable part  50  of the mandrel  37  is fitted in a projecting manner on the fixed part  49  of the mandrel  37  so as to linearly slide relative to the fixed part  49 . 
     In each mandrel  37 , the expanded configuration (illustrated in  FIG.  13   ) confers the largest, i.e. maximum, cross section to the mandrel  37 , which is equal, with a substantially null clearance, to the inner cross section of the cardboard box  2  while the contracted configuration (illustrated in  FIG.  14   ) confers the smallest, i.e. minimum, cross section to the mandrel  37 , which is substantially smaller than the inner cross section of the cardboard box  2 . For each mandrel  37  the expanded configuration (illustrated in  FIG.  13   ) is used during the folding of the blank  9  because the expanded configuration allows to obtain a very precise and straight folding of the blank  9  (i.e. it allows to obtain the maximum folding quality) and the contracted configuration (illustrated in  FIG.  14   ) is used only when the empty cardboard box  2  has to be unravelled from the mandrel  37  in that, by creating a clearance between the empty cardboard box  2  and the mandrel  37  it is much easier (i.e. it requires less force and therefore does not damage the cardboard box  2  that has just been formed) to unravel the empty cardboard box  2  from the mandrel  37 . 
     Accordingly, along the folding path P 2 , the mandrels  37  assume the expanded configuration everywhere except in the transfer station S 3  and the mandrels  37  assume the contracted configuration only in the transfer station S 3 . 
     Normally, the sizing of the cross section of a mandrel is always a compromise between the antithetical necessity of giving the mandrel an equal cross section, with a substantially null clearance, to the inner cross section of the cardboard box in order to obtain an optimal folding and to confer a cross section much smaller than the inner cross section of the cardboard box to the mandrel, so as to allow an easy unravelling of the cardboard box from the mandrel once the forming of the cardboard box has been completed (i.e. without having to exert a very high force on the cardboard box, which could damage the cardboard box, but that is necessary to overcome the friction between the inner surface of the cardboard box and the outer surface of the mandrel). In the folding unit  20  of the packaging machine  18  described above, this compromise (second-rate, as it obliges the penalization of both the quality of the folding and the ease of extraction) is completely avoided by using the mandrels  37  which can modify its cross section due to the mutual movement between the two parts  49  and  50 , thus presenting in each situation the optimum cross section. In other words, when the mandrels  37  must be “large” to optimize the folding of the blank  9  the mandrels assume the expanded configuration (illustrated in  FIG.  13   ) whereas when mandrels  37  must be “small” to optimize the extraction of the empty 2 cardboard boxes, that just have been formed, the mandrels assume the contracted configuration (illustrated in  FIG.  14   ). 
     The displacement of the mandrels  37  between the expanded configuration and the contracted configuration is preferably controlled, but not necessarily, by a camming system  51  (schematically shown in  FIGS.  13  and  14   ) which takes motion from the rotation of the folding drum  34  around the rotation axis  35 . Among other things, the camming system  51  comprises, for each mandrel  37 , a slider  52  which is axially movable (i.e. parallel to the rotation axis  43 ) and controls the movement of the mandrel  37  between the expanded configuration (illustrated in  FIG.  13   ) and the contracted configuration (illustrated in  FIG.  14   ). According to a preferred but non-binding embodiment, the camming system  51 , that controls the movement of the parts  49  and  50  of each mandrel  37 , is devoid of elastic elements. 
     In the embodiment illustrated in the accompanying figures, in each mandrel  37  the movement of the movable part  50  relative to the fixed part  49  determines the variation in the size (cross section) of the mandrel  37  only in one direction (in particular in the width and not in the thickness and in axial length). According to an alternative embodiment not illustrated, in each mandrel  37  the movement of the movable part  50  relative to the fixed part  49  determines the variation in the size (cross section) of the mandrel  37  only in two directions perpendicular to one another (in particular in the width and in the thickness and not in axial length). 
     As illustrated in  FIG.  15   , the insertion unit  21  comprises the refining conveyor  44  which is in common with the subsequent closing unit  22 ; in other words, the same refining conveyor  44  feeds the cardboard boxes  2  containing the groups  3  of articles (i.e. the packages  1 ) both through the insertion unit  21 , and through the subsequent closing unit  22 . The refining conveyor  44  feeds a series of refining pockets  53  along a straight and horizontal refining path P 4  which is parallel and flanked to the formation path P 1 ; preferably, the refining conveyor  44  comprises (at least) a flexible belt which is closed in a loop around two end pulleys (at least one of which is motorized) and supports the refining pockets  53 . 
     The refining conveyor  44  is arranged, for a given section, beside the formation conveyor  23 , that is, at the insertion unit  21 , an initial section of the refining conveyor  44  is flanked by a final section of the formation conveyor  23 . Furthermore, the initial section of the refining conveyor  44  is arranged at the transfer station S 3 . In use, the folding drum  34  of the folding unit  20  feeds the empty cardboard boxes  2 , that have just been formed, in the transfer station S 3  to the refining conveyor  44  of the insertion unit  21 ; in other words, in the transfer station S 3  the empty cardboard boxes  2 , that have just been formed, are cyclically transferred from the folding heads  36  of the folding drum  34  to the refining pockets  53  of the refining conveyor  44 . This transfer can take place directly (i.e. the empty cardboard boxes  2 , that have just been formed, pass directly from the folding heads  36  of the folding drum  34  to the refining pockets  53  of the refining conveyor  44  without intermediaries) or this transfer can take place indirectly (i.e. between the folding drum  34  and the refining conveyor  44  an intermediate conveyor is interposed, which receives in delivery the empty cardboard boxes  2 , that have just been formed, it passes from the folding heads  36  of the folding drum  34  and subsequently releases the empty cardboard boxes  2 , that have just been formed, to the refining pockets  53  of the refining conveyor  44 ). 
     As previously stated, to release an empty cardboard box  2 , that has just been formed, the corresponding folding head  36  arranges the empty cardboard box  2  in the destination (for example a refining pocket  53  of the refining conveyor  44 ) and then moves (axially translates) its own mandrel  37  (which is in the contracted configuration to facilitate the axial unravelling) from the work position to the rest position; said axial movement of the mandrel  37  determines the axial unravelling of the mandrel  37  from the empty cardboard box  2 , that has just been formed, and therefore the empty cardboard box  2 , that has just been formed, is released from the folding head  36  and remains engaged only by the destination (for example a refining pocket  53  of the refining conveyor  44 ). In other words, for a small period of time the empty cardboard box  2 , that has just been formed, is engaged both by the destination (for example a refining pocket  53  of the refining conveyor  44 ) and by the mandrel  37  of the folding head  36 ; when the mandrel  37  of the folding head  36  moves (axially translates) from the work position to the rest position, the mandrel  37  is axially unravelled from the empty cardboard box  2 , that has just been formed, leaving the empty cardboard box  2 , that has just been formed, only in the destination (for example a refining pocket  53  of the refining conveyor  44 ). 
     As better illustrated in  FIGS.  11  and  12   , each folding head  36  comprises a support body  46  which is hinged to the folding drum  34  so as to rotate around the corresponding rotation axis  43 . In each folding head  36  the body  46  that carries the mandrel  37  which is mounted on the support body  46  to axially slide along an axial translational direction, i.e. parallel to the rotation axis  43 , between a work position (illustrated for example in  FIGS.  11  and  12   ), in which the mandrel  37  protrude from the folding drum  34 , and a release position, in which the mandrel  37  does not protrudes in a cantilever fashion from the folding drum  34 . Along the folding path P 2 , the mandrels assume the work position everywhere except in the transfer station S 3  and the mandrels  37  assume the release position only in the transfer station S 3  (according to methods better described in the following). 
     The insertion unit  21  comprises a series of pushers  54  which move the paths P 1  and P 4 , in parallel, synchronously with the conveyors  23  and  44  and push the groups  3  of articles from the formation pockets  24  of the formation conveyor  23  into the refining pockets  53  of the refining conveyor  44 , i.e. inside the empty 2 cardboard boxes carried by the refining pockets  53  of the refining conveyor  44 . The insertion unit  21  comprises an actuator device which moves the pusher  54  by imparting, to the pushers  54 , both a feed movement parallel to the paths P 1  and P 4  and synchronized with the two conveyors  23  and  44 , and an insertion movement perpendicular to the paths P 1  and P 4 . 
     In other words, in the insertion unit  21  each group  3  of articles is longitudinally inserted into a corresponding empty cardboard box  2 : the formation conveyor  23  advances with continuous motion synchronously with the refining conveyor  44  and the pushers  54  advance with a continuous motion synchronously with the two conveyors  23  and  44  and are moving perpendicularly to the paths P 1  and P 4  for axially transferring each group  3  of articles from a formation pocket  24  of the formation conveyor  23  to a refining pocket  53  of the refining conveyor  44 . 
     The closing unit  22  comprises folding devices (per se of known type) which fold the fins  17  against one another to close the cardboard boxes  2  and then complete the formation of the packages  1 . The closing unit  22  comprises, furthermore, gluing devices, which are arranged near the refining conveyor  44  and along the refining path P 4  for applying glue (preferably hot, i.e. preferably quick-setting) to the fins  17 ; preferably, the gluing devices of the closing unit  22  are of the spraying type, i.e. it comprises one or more glue guns which are activated to supply a pressurized spray of glue towards the fins  17 . 
     According to a possible illustrated embodiment, the closing unit  22  comprises a printing device (for example an ink jet printer), which is arranged along the refining conveyor  44  to print at least one identification code (for example containing packaging date and place) on a wall of each cardboard box  2  carried by the refining conveyor  44 . 
     The embodiments described herein can be combined without departing from the scope of protection of the present invention. 
     The packaging machine  18  described above has numerous advantages. 
     First of all, the packaging machine  18  described above allows to achieve high hourly productivity while ensuring a high-quality standard. 
     Furthermore, the packaging machine  18  is relatively compact and relatively inexpensive as it directly performs the folding of the blanks  9 , i.e. it receives the flat blanks  9  devoid of any prior folding. 
     These results are obtained mainly, but not exclusively, by the fact of using mandrels  37  of variable size which become “large” to optimize the folding of the blank  9  and become “small” to optimize the unravelling of the empty cardboard boxes  2  that has just been formed; in this way it is possible to obtain, at the same time, a high hourly productivity and also a high quality standard. 
     Following the advantages obtainable with the use of mandrels  37  of variable size, the use of mandrels  37  of variable size can also be applied to the manufacture of empty cardboard boxes  2  which are adapted to contain products other than those described above (also outside of the tobacco field). In other words, the use of mandrels  37  of variable size is not limited to the manufacturing of empty cardboard boxes  2  designed to contain the groups  3  of heterogeneous articles described above, but the use of mandrels  37  of variable size can find advantageous application in the manufacturing of empty cardboard boxes  2  adapted to contain any type of product (also outside the tobacco field).