Abstract:
A method and machine for producing a packet, whereby, as it is fed along a feed path, a substantially flat blank with preformed fold lines is extracted from the feed for transfer, crosswise to the feed path, to a stretch-folding station for stretching at least some of the fold lines, and is then fed back onto the feed path and allowed to spring back to its original flat shape.

Description:
[0001]    The present invention relates to a method of producing a packet.  
           [0002]    The present invention may be used to advantage in the packing of cigarettes, to which the following description refers purely by way of example.  
         BACKGROUND OF THE INVENTION  
         [0003]    In recent times, demand has risen for packets of cigarettes with other than sharp edges. e.g. rounded-edged packets.  
           [0004]    A flat blank from which to produce a rounded-edged packet calls for careful processing. In particular, in view of the high operating speed of modern packing machines, portions of the blank eventually forming the rounded edges of the packet must often be stretched before the blank is folded about a group of cigarettes enclosed in foil wrapping.  
           [0005]    For this purpose, some known packing machines comprise a linear conveyor for feeding the blank to a folding wheel; and fixed stretch-folding rails located on opposite sides of the linear conveyor to fold flaps on the blank and so stretch desired portions of the blank. At the end of the fixed rails, the blank springs back to its original substantially flat configuration, and is then fed to the folding wheel.  
           [0006]    The stretch-folding rails are relatively bulky, and, in particular, make servicing of the conveyor awkward, fail to provide for precise stretch, and may even damage the blank due to slippage.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide a method of producing a packet, designed to eliminate the aforementioned, and which, at the same time, is cheap and easy to implement.  
           [0008]    According to the present invention, there is provided a method of producing a packet from a blank having at least one substantially flat first portion comprising preformed fold lines; the method comprising the steps of feeding said blank along a feed path, and performing a stretching operation on at least some of said preformed fold lines; and the method being characterized in that said stretching operation is performed off said feed path by extracting said blank from a given point along said feed path, transferring the blank to a stretch-folding station in a given direction, stretching said preformed fold lines at said stretch-folding station, and restoring the stretched blank to said feed path.  
           [0009]    To improve stretch, in the method as defined above, at least one portion of the blank is preferably wrapped about a folding spindle at said stretch-folding station, so as to define, on said portion, two second portions forming an angle of less than 90°.  
           [0010]    The present invention also relates to a machine for producing a packet.  
           [0011]    According to the present invention, there is provided a machine for producing a packet from a blank having at least one substantially flat portion comprising preformed fold lines; the machine comprising a conveyor for feeding the blank along a path, and a stretch-folding device for stretching at least some of said preformed fold lines at a stretch-folding station; the machine being characterized in that the stretch-folding station is located off said path, and the stretch-folding device comprises a transfer unit for transferring the blank in a given direction from a transfer station, located along the conveyor, to the stretch-folding station, and for transferring the stretched blank from the stretch-folding station to the transfer station. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:  
         [0013]    [0013]FIG. 1 shows a schematic, partly sectioned front view of a stretch-folding device of a machine for producing packets of cigarettes in accordance with the present invention;  
         [0014]    [0014]FIG. 2 shows the FIG. 1 stretch-folding device at a successive operating step;  
         [0015]    [0015]FIG. 3 shows a blank folding step to produce a packet of cigarettes;  
         [0016]    [0016]FIG. 4 shows a finished packet of cigarettes. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    Number  1  in FIG. 1 indicates as a whole a machine for producing a rigid packet  2  of cigarettes (FIG. 4). Packet  2  comprises a cup-shaped body  3  and a lid  4  hinged to cup-shaped body  3 . Cup-shaped body  3  comprises a front wall  5 , two lateral walls  6  (only one shown in FIG. 4), a bottom wall  7 , and a known rear wall (not shown). Lid  4  comprises a front wall  5   a,  two lateral walls  6   a  (only one shown in FIG. 4), and a known top and rear wall (not shown). Lateral walls  6  and  6   a  are connected to respective front walls  5  and  5   a  and the respective rear walls by relative rounded edges  8 .  
         [0018]    Packet  2  is formed from a substantially flat blank  9  (shown partly folded in FIG. 3) comprising a central portion  10  and a number of lateral panels  11  located symmetrically on opposite sides of portion  10 . Portion  10  comprises a number of panels aligned along the longitudinal dimension of blank  9 . Each panel  11  is connected to portion  10  by a respective substantially flat connecting portion  12  having preformed fold lines  13 . Once folded, connecting portions  12  correspond to rounded edges  8  of packet  2 .  
         [0019]    With reference to FIGS. 1 and 2, machine  1  comprises a linear step conveyor  14  for feeding blank  9  along a feed path P and through a transfer station  15  of a stretch-folding device  16 . Conveyor  14  comprises two parallel belts  17  (only one shown in FIGS. 1 and 2) moving discontinuously in a substantially horizontal travelling direction A; and two clamping members  18 , each connected integrally and crosswise to both belts  17 . The two clamping members  18  laterally define a seat  19  for housing blank  9  in a substantially horizontal position.  
         [0020]    Stretch-folding device  16  comprises a transfer unit  20  for transferring blank  9  from transfer station  15  to a stretch-folding station  21 . Transfer unit  20  comprises a folding spindle  22 ; and a hydraulic actuator  23  for moving spindle  22  from transfer station  15  to stretch-folding station  21  in a substantially vertical direction crosswise to direction A. More specifically, in use, when blank  9  is located at transfer station  15  and conveyor  14  is stationary, actuator  23  lifts spindle  22  through a gap between belts  17 , so that spindle  22  intercepts blank  9  and, supporting it in a horizontal position from underneath, feeds it to stretch-folding station  21 .  
         [0021]    Spindle  22  has two rounded edges  24 , about which portions  12  are folded in use, and comprises a suction head  25  for securing blank  9  to spindle  22 . In this connection, it should be pointed out that the relative positions and the dimensions of blank  9  and spindle  22  are such that, when blank  9  is positioned on top of spindle  22 , panels  11  project, unsupported, from edges  24  of spindle  22 .  
         [0022]    Spindle  22  also has a top surface  22   a,  on which blank  9  rests in use; and two lateral surfaces  22   b  connected to the top surface by edges  24  and converging downwards.  
         [0023]    Stretch-folding device  16  also comprises a counter-folding spindle  26  located at stretch-folding station  21  and which cooperates with spindle  22  to wrap blank  9  at least partly about spindle  22  and so stretch portions  12 .  
         [0024]    Counter-folding spindle  26  comprises a contrasting plate  27  which, as blank  9  is being folded, rests on top of blank  9  to keep it correctly positioned on top surface  22   a  of spindle  22 .  
         [0025]    Counter-folding spindle  26  also comprises a pocket  28 , into which spindle  22  supporting blank  9  is inserted in use; and two arms  29  on opposite sides of pocket  28 . Each arm  29  rotates about a respective substantially horizontal axis  30  of rotation (therefore parallel to the plane of blank  9  at stretch-folding station  21 ), and comprises a relative substantially cylindrical folding pin  31  which, rotating about relative axis  30 , follows the contour of respective edge  24  to push relative panels  11  downwards.  
         [0026]    In actual use, a first branch  14   a  of conveyor  14  feeds blank  9  to transfer station  15 . As blank  9  stops at transfer station  15 , hydraulic actuator  23  is activated to raise spindle  22 , so that spindle  22  intercepts blank  9 . As spindle  22  intercepts blank  9 , suction head  25  is activated to prevent blank  9  moving with respect to spindle  22 . At this point, spindle  22  lifts blank  9  into pocket  28 , and, as blank  9  is being inserted inside pocket  28 , pins  31  of arms  29  contact and push panels  11  down to stretch portions  12 .  
         [0027]    In this connection, it should be pointed out that, by virtue of the orientation of lateral surfaces  22   b  and the structure of counter-folding spindle  26 , portions  12  are so folded (as shown in FIG. 2) that panels  11  rest on lateral surfaces  22   b  and so form, with respect to portion  10 , an angle of less than 90°, which provides for effectively stretching portions  12 .  
         [0028]    Once stretching is completed, spindle  22 , together with blank  9 , is lowered to replace blank  9  inside seat  19  at transfer station  15 . As it is being transferred back to seat  19 , blank  9  springs back to its original substantially flat shape, and, once the blank is positioned inside seat  19 , suction head  25  is deactivated.  
         [0029]    At this point, belts  17  are activated, and blank  9  is fed along a second branch  14   b  (parallel to branch  14   a ) of conveyor  14  to a further known processing station not shown. Further processing steps comprise folding blank  9  about a group  32  of cigarettes (FIG. 3).  
         [0030]    In an embodiment not shown, branches  14   a  and  14   b  of conveyor  14  are substantially crosswise to each other.  
         [0031]    Though the above description and accompanying drawings relate to a rounded-edged packet  2  of cigarettes, the teachings of the present invention obviously also apply to any type of packet, in particular, packets of cigarettes of any type, e.g. square- or bevelled-edged hinged-lid packets, or so-called “pillow” packets, i.e. having sharp edges and one or more curved portions on the front, rear, top, bottom and/or lateral walls. Obviously, the shape of spindle  22  and counter-folding spindle  26  must be adapted to the shape of the edges to be formed.  
         [0032]    Also, though the above description and accompanying drawings relate to stretching longitudinal edges  8  of packet  2 , the teachings of the present invention obviously also apply to stretching transverse edges of a packet.