Abstract:
A method and unit for forming a tubular wrapping about a rectangular-prism-shaped product, whereby a sheet of packing material is folded about the product in a first folding step, wherein the sheet of packing material is folded into a U about the product so that an end portion of the sheet of packing material projects crosswise with respect to a longitudinal axis of the product and beyond the product itself; and in a second folding step, wherein the end portion is subjected to traction in a direction crosswise to the longitudinal axis of the product, and is simultaneously folded further about the product to define the tubular wrapping

Description:
[0001]    The present invention relates to a method of forming a tubular wrapping about a product.  
           [0002]    More specifically, the present invention relates to a method of forming a tubular wrapping about a substantially rectangular-prism-shaped product, the method being of the type comprising a first folding step in which a sheet of packing material is folded into a U about the product so that an end portion of the sheet projects crosswise to a longitudinal axis of the product and beyond the product itself; and a second folding step in which said end portion is folded further about the product to define said tubular wrapping.  
           [0003]    The present invention may be used to advantage in the tobacco industry for forming tobacco products into packets or packs, and in particular for forming products defined by groups of packets of cigarettes into cartons, to which the following description refers purely by way of example.  
         BACKGROUND OF THE INVENTION  
         [0004]    In the tobacco industry, cartoning machines are used, on which a folding unit is supplied with a succession of groups of packets of cigarettes and relative sheets of packing material—which may be paper or transparent material such as polypropylene—and performs the two folding steps described above to form, about each group of packets, a tubular wrapping coaxial with the longitudinal axis of the group.  
           [0005]    U.S. Pat. No. 5,305,580 discloses a machine and a method for forming tubular wrapping about a rectangular-prism-shaped product, in particular a packet of cigarettes. According to such a method a sheet of packing material is folded about the product so as to define the tubular wrapping by means of a rotation of the product around its longitudinal axis.  
           [0006]    Experience has shown that, whereas, given the way it is normally carried out, the first folding step normally results in the sheet of packing material adhering perfectly to the group of packets of cigarettes, the same does not always apply to the second step with regard to the projecting end portion of the sheet.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide a packing method designed to eliminate the aforementioned drawback, and which, at the same time, provides for fast, precise wrapping and reduced maintenance. A further object of the present invention is to provide a method which is cheap and easy to implement.  
           [0008]    According to the present invention, there is provided a method of forming a tubular wrapping about a rectangular-prism-shaped product, the method comprising a first folding step in which a sheet of packing material is folded into a U about the product so that an end portion of the sheet of packing material projects crosswise to a longitudinal axis of the product and beyond the product itself; and a second folding step in which said end portion is folded further about the product to define said tubular wrapping; and being characterized in that said end portion is subjected, in the course of said second folding step, to traction in a direction crosswise to said longitudinal axis; said first folding step being performed by placing said sheet of packing material in front of, and so as to close, an inlet of a U-shaped pocket for said product; and inserting the product and said sheet of packing material inside said pocket by moving said product against said sheet of packing material and through said inlet.  
           [0009]    The present invention also relates to a unit for forming a tubular wrapping.  
           [0010]    According to the present invention, there is provided a unit for forming a tubular wrapping about a rectangular-prism-shaped product having a longitudinal axis, the unit comprising first folding means for folding a sheet of packing material into a U about said product so that an end portion of the sheet of packing material projects crosswise to said longitudinal axis and beyond said product; and second folding means for folding said end portion about said product to define said tubular wrapping; and being characterized by also comprising braking means associated with said second folding means and for subjecting said end portion to traction in a direction crosswise to said longitudinal axis. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    A nonlimiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 shows a side view of a preferred embodiment of the folding unit according to the present invention;  
         [0013]    [0013]FIG. 2 shows, in perspective, a folding sequence for folding a sheet of packing material about a product. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]    Number  1  in FIG. 1 indicates as a whole a packing unit for forming, as shown in FIG. 2, a tubular wrapping  2  about a rectangular-prism-shaped product  3  having a longitudinal axis  4 . In the example shown, product  3  is defined by a group of packets  5  of cigarettes arranged side by side along longitudinal axis  4  in two superimposed layers; and tubular wrapping  2  is coaxial with longitudinal axis  4  and formed by folding a sheet  6  of packing material about product  3  in a direction crosswise to longitudinal axis  4 . More specifically, product  3  is defined laterally by two major lateral surfaces  7  and  8  parallel to each other and to longitudinal axis  4 , and by two minor lateral surfaces  9  and  10  parallel to each other and to longitudinal axis  4 , and perpendicular to major lateral surfaces  7  and  8 .  
         [0015]    As shown in FIG. 1, unit  1  comprises a packing wheel  11  fitted to a powered shaft  12 , which has an axis  13 , perpendicular to the FIG. 1 plane, and is rotated in 180° steps about axis  13  in a direction  14  (clockwise in FIG. 1).  
         [0016]    Along its outer periphery, packing wheel  11  has two diametrically opposite radial pockets  15 , each of which extends, parallel to axis  13 , along packing wheel  11 , is open both radially outwards and at the axial ends, and is defined by an end wall  16  parallel to axis  13  and having a longitudinal opening  17  parallel to axis  13 , and by two facing lateral walls  18  and  19  parallel to axis  13  and perpendicular to end wall  16 . Lateral wall  18  is located upstream from lateral wall  19  in direction  14 ; and lateral walls  18  and  19  of each pocket  15  define, together with relative end wall  16 , a relative rectangular-prism-shaped seat  20  for receiving a relative product  3  positioned with its longitudinal axis  4  parallel to axis  13 .  
         [0017]    Unit  1  also comprises a loading station  21  and an unloading station  22  located diametrically opposite each other outside packing wheel  11 , which, at each rotation step of shaft  12  in direction  14 , transfers one pocket  15  from loading station  21  to unloading station  22  along a packing path P 1 , and the other pocket  15  from unloading station  22  to loading station  21  along a return path P 2 .  
         [0018]    Loading station  21  comprises a pusher  23 , which moves back and forth in a radial direction  24  with respect to axis  13 , and cooperates with the minor lateral surface  10  of a product  3 —located at loading station  21  with longitudinal axis  4  parallel to axis  13 —to insert product  3  inside a pocket  15 —arrested at loading station  21 —so that product  3  is positioned, inside relative seat  20 , with minor lateral surface  9  substantially contacting relative end wall  16 , with major lateral surfaces  7  and  8  substantially contacting relative lateral walls  18  and  19 , and with minor lateral surface  10  flush with an inlet  25  of relative seat  20  and with the outer periphery of packing wheel  11 .  
         [0019]    Unloading station  22  comprises an unloading guide  26  located outside packing wheel  11  and comprising two facing plates  27  and  28  parallel to each other, to axis  13  and to direction  24 , and of which plate  28  is located downstream from plate  27  in direction  14 . More specifically, plates  27  and  28  are separated by a distance equal to the distance between walls  18  and  19  of each pocket  15 , and approximately equal to but no less than the distance between major lateral surfaces  7  and  8  of product  3 , and define, between them, an unloading passage  29  for unloading products  3 . Plate  27  projects, with respect to plate  28 , towards the periphery of packing wheel  11 , and is defined, towards packing wheel  11 , by an end folding edge  30  parallel to axis  13  and positioned substantially contacting the outer periphery of packing wheel  11  and substantially tangent to the path, coincident with paths P 1  and P 2 , of inlets  25  of seats  20  of pockets  15 . Unloading station  22  also comprises a pusher  31 , which moves back and forth in direction  24  and cooperates, through opening  17  in a pocket  15  arrested at unloading station  22 , with the minor lateral surface  10  of a product  3  housed inside said pocket  15 , to expel product  3  from relative seat  20  to unloading guide  26  through unloading passage  29 .  
         [0020]    Unit  1  also comprises a substantially semicylindrical fixed guide plate  32  coaxial with axis  13  and defined internally by a semicylindrical surface  33  extending along packing path P 1  between loading station  21  and unloading station  22 . Plate  32  is defined, at the end immediately downstream from loading station  21  in direction  14 , by an end folding edge  34  parallel to axis  13 , and, immediately upstream from unloading station  22 , extends through a braking station  35  comprising an opening  36  formed through plate  32  and parallel to axis  13 , and a hammer  37  of a gripper-type braking device  38 .  
         [0021]    Hammer  37  comprises a lever  39  located outside plate  32  and hinged to a frame  39   a  to rotate, with respect to plate  32 , about an axis  40  parallel to axis  13 ; a pad  41  made of resilient material, fitted integrally to a free end of lever  39 , facing plate  32 , and movable through opening  36  when lever  39  is rotated about axis  40 ; and a spring  42  for normally keeping pad  41  in a work position engaging opening  36  and interfering with packing path P 1 .  
         [0022]    In addition to hammer  37 , braking device  38  comprises, for each pocket  15 , an anvil  43  movable with relative pocket  15  along paths P 1  and P 2  and comprising a bracket  44  integral with an outer surface of relative lateral wall  18 , and a roller  45 , which extends along the whole length of relative pocket  15  in the direction of axis  13 , is substantially the same length as pad  41 , and is fitted to relative bracket  44  to rotate idly, with respect to relative pocket  15 , about an axis  46  parallel to axis  13 . Roller  45  has at least one peripheral portion made of resilient material, and is positioned with its outer surface tangent to the plane of inlet  25  of relative seat  20 .  
         [0023]    In actual use, simultaneously with the arrest of an empty pocket  15  at loading station  21 , a sheet  6  of packing material (FIGS. 1 and 2 a ) is fed through loading station  21 , along a plane P 3  tangent to the outer periphery of packing wheel  11  and in a direction  47  crosswise to axis  13 , and is arrested with a first intermediate portion  48  facing relative inlet  25  and interposed between inlet  25  and the minor lateral surface  9  of a product  3  ready for loading at loading station  21 , and with an end portion  49 , generally narrower than major lateral surfaces  7  and  8  of product  3 , projecting upstream from relative inlet  25 .  
         [0024]    Pusher  23  is then activated (FIGS. 1 and 2 b ) to insert product  3  and relative sheet  6  of packing material inside relative seat  20  through relative inlet  25 , and so fold sheet  6  of packing material into a U about relative product  3 . More specifically, following insertion, sheet  6  of packing material is folded about relative product  3  with end portion  49  contacting part of major lateral surface  7  of relative product  3  and between major lateral surface  7  and lateral wall  18  of relative pocket  15 ; with intermediate portion  48  contacting minor lateral surface  9  of relative product  3  and between minor lateral surface  9  and end wall  16  of relative pocket  15 ; with a further intermediate portion  50  contacting major lateral surface  8  of relative product  3  and between major lateral surface  8  and lateral wall  19  of relative pocket  15 ; and with an end portion  51 , opposite end portion  49 , projecting radially outwards from relative seat  20  through relative inlet  25  and coplanar with the inner surface of lateral wall  19  of relative pocket  15 .  
         [0025]    As packing wheel  11  is then fed one step in direction  14 , end portion  51  contacts end edge  34  of plate  32  and is folded backwards (FIGS. 1 and 2 c ) so that a portion  52  of end portion  51  contacts minor lateral surface  10  of relative product  3 , and an end portion  53  of end portion  51 , opposite end portion  49  and generally slightly narrower than major lateral walls  7  and  8 , projects rearwards of relative inlet  25 , is substantially coplanar with minor lateral surface  10  of relative product  3 , and contacts the outer surface of relative roller  45 , the distance of which from the rear end of relative inlet  25  is less than the width of end portion  53 .  
         [0026]    Sheet  6  of packing material remains in this position up to unloading station  22 , where, upon operation of pusher  31 , end portion  53  is brought into contact with and folded backwards by end edge  30  of plate  27 , and, as relative product  3  is inserted inside unloading guide  26 , is positioned contacting major lateral surface  7  of relative product  3  and overlapping end portion  49  to complete relative tubular wrapping  2 .  
         [0027]    Along the final portion of packing path P 1 , the pocket  15  considered is fed through braking station  35 , where pad  41  frictionally engages portion  52  of sheet  6  of packing material, so as to exert braking action on the whole of end portion  51 , which is thus maintained contacting minor lateral surface  10  of relative product  3  by tension acting in a direction  54  (FIG. 2 c ) opposite direction  14 .  
         [0028]    As the pocket  15  considered is arrested at unloading station  22 , relative roller  45  is arrested facing opening  36 , the distance of which from the upstream end of unloading passage  29  equals the distance between roller  45  and the upstream end of inlet  25  of relative seat  20 . Consequently, as the pocket  15  considered is arrested facing unloading passage  29 , the tension applied by pad  41  to end portion  51 , as a consequence of the rotation of packing wheel  11  and the friction between pad  41  and end portion  51 , is maintained by virtue of end portion  53  being gripped between pad  41  and relative roller  45 . The same tension is also maintained as product  3  and relative sheet  6  of packing material are inserted inside unloading guide  26  through unloading passage  29  and as end portion  53  is folded, by virtue of end portion  53 , as it is folded, still being gripped between hammer  37  and relative anvil  43  of braking device  38 , and sliding frictionally between pad  41  and relative roller  45  arrested facing each other with pad  41  pressed against roller  45  by spring  42 .  
         [0029]    In other words, braking device  38  provides for forming a tubular wrapping  2  adhering perfectly to the lateral surface of relative product  3 .  
         [0030]    In connection with the above, it should be stressed that braking device  38  is totally passive, and requires no power or control device for its operation.  
         [0031]    Obviously, braking device  38  may be replaced with any type of active braking device, such as a suction device (not shown), associated with plate  32 .