Abstract:
A method of wrapping elongated articles in groups provides for feeding a first and a second pocket continuously along two respective paths having a common portion, along which the first pocket penetrates the second pocket to transfer a group from the first to the second pocket together with a sheet of wrapping material, which is folded into a U inside the second pocket and has two parallel, opposite flaps gripped between first and second lateral walls; and for compressing the group between a first and a second bottom wall and, at the same time, extracting the first lateral walls from the second pocket.

Description:
The present invention relates to a method of wrapping elongated articles in groups. 
     More specifically, the present invention relates to a method of wrapping orderly groups of cigarettes, to which the following description refers purely by way of example. 
     BACKGROUND OF THE INVENTION 
     Methods of wrapping orderly groups of cigarettes—hereinafter referred to simply as “groups”—normally comprise folding a sheet of wrapping material about a group to form a tubular wrapping; and closing two tubular portions, projecting from opposite ends of the group, onto the group itself. Formation of the tubular wrapping comprises a first folding step wherein the sheet of wrapping material is folded into a U; a second folding step wherein a first free flap of the sheet of wrapping material is folded into an L; and a third folding step wherein a second free flap of the sheet of wrapping material is folded into an L onto a third flap folded onto the group when making the U-shaped fold. 
     In known methods of a first type, the group is inserted inside a metal spindle, and a sheet of wrapping material is folded about the spindle. Methods of this type provide for forming sharp-edged folds—particularly appreciated in the cigarette manufacturing industry—but involve extracting the spindle from the tubular wrapping, thus slowing down the wrapping unit as a whole. 
     In known methods of a second type, the sheet of wrapping material is folded directly about the group, so that the tubular wrapping has rounded edges with a radius of curvature substantially equal to the diameter of the cigarettes. 
     Given the current emphasis, in automatic machine design, on producing continuously-operating machines to increase output, wrapping methods of the first type are more or less discarded, by extraction of the group and wrapping from the spindle not being adaptable to continuously-operating machines. 
     One known method of wrapping groups on a continuously-operating machine normally comprises feeding a first and a second pocket continuously along a first and, respectively, second path having a common portion, along which the first pocket penetrates the second pocket to transfer an orderly group of cigarettes from the first to the second pocket together with a sheet of wrapping material, which is folded into a U, when transferring the group, and is then folded about the group by folding devices located along the second path. The first pocket comprises a first bottom wall and two lateral walls, and the second pocket comprises a second bottom wall and second lateral walls. When making the U-shaped fold, a portion of the sheet of wrapping material is gripped between the group and the second bottom wall; and two opposite, parallel flaps of the sheet of wrapping material are gripped between the first and second lateral walls. The first and second pocket are then fed separately along the respective paths, and the first pocket, obviously, is extracted from the second. When extracting the first lateral walls, the sheet of wrapping material may slip with respect to the second pocket and to the group housed inside the second pocket, even to the extent of impairing subsequent folds and formation of the wrapping as a whole. On the other hand, it is extremely difficult to determine the conditions resulting in such a difference in friction between the two first lateral walls and the flaps as to cause slippage of the sheet of wrapping material. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method of wrapping elongated articles in groups, which may be implemented easily on an automatic, continuously-operating machine of the type described above, and which at the same time provides for preventing slippage of the sheet of wrapping material during the folding operations. 
     According to the present invention, there is provided a method of wrapping elongated articles in groups, the method comprising feeding a first and a second pocket continuously along a first and, respectively, second path having a common portion, along which the first pocket penetrates the second pocket to transfer a group from the first to the second pocket together with a sheet of wrapping material, the first and the second pocket comprising, respectively, a first and a second bottom wall, and first and second lateral walls; gripping a first and a second flap, opposite and parallel to each other, of the sheet of wrapping material between the first and second lateral walls; and extracting the first lateral walls from the second pocket; the method being characterized by compressing the group and a portion of the sheet of wrapping material between the first and second bottom wall when extracting the first lateral walls from the second pocket. 
     In other words, the sheet of wrapping material is compressed to prevent slippage of the sheet caused by extraction of the first lateral walls from the second pocket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
     FIG. 1 shows a schematic side view, with parts in section and parts removed for clarity, of a unit for wrapping elongated articles in groups and implementing the method according to the present invention; 
     FIGS. 2,  3 ,  6 ,  7 ,  11  and  13  show side views, with parts in section and parts removed for clarity, of a detail of the FIG. 1 unit at successive steps in the method according to the present invention; 
     FIGS. 4,  5  show larger-scale side views of details in FIG. 3; 
     FIG. 8 shows a larger-scale side view of a detail in FIG. 7; 
     FIG. 9 shows a section, with parts removed for clarity, of a detail in FIG. 1; 
     FIG. 10 shows a view in perspective of the FIG. 9 detail; 
     FIG. 12 shows a larger-scale side view of a detail in FIG.  11 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, number  1  indicates as a whole a unit for wrapping cigarettes  2  arranged in groups  3  on an automatic, continuously-operating wrapping machine not shown. Unit  1  comprises two wheels  4  and  5  shown by the dash lines in FIG.  1  and fitted to a structure S to rotate about respective parallel axes (not shown) perpendicular to the FIG. 1 plane. Wheels  4  and  5  respectively support two successions of pockets  6  and  7 , only two of which are shown in FIG. 1, and which respectively travel along two endless paths P 1  and P 2  having a common portion T. Unit  1  also comprises two folding devices  8  and  9  located along path P 2  and cooperating with pocket  7 . 
     Pocket  6  comprises a frame  10  fitted to wheel  4  to rotate about an axis  11  perpendicular to the FIG. 1 plane; and a bottom wall  12  and two lateral walls  13  fixed to frame  10 . Bottom wall  12  is movable with respect to frame  10  along an axis A 1 , and is integral with a rod  14  fitted in sliding manner to frame  10 , and with a cam actuating device  16 . 
     Lateral walls  13  are defined by two thin, flat, facing plates parallel to each other and to axis A 1  and fixed rigidly to frame  10 . 
     Downstream from each pocket  6 , wheel  4  supports a gripper  17  extending radially from wheel  4 , and which provides for withdrawing the end of a sheet  18  of wrapping material from a known device (not shown), and for drawing sheet  18  of wrapping material in front of pocket  6  along a portion of path P 1 . 
     Each pocket  7  comprises a frame  19  fitted to wheel  5  to rotate about an axis  20  parallel to axis  11 ; a bottom wall  21  and two lateral walls  22  and  23 ; a jaw  24 ; and two plates  25  supported on U-shaped arms  26  and shown in FIGS. 9 and 10. 
     With reference to FIG. 1, bottom wall  21  is movable along an axis A 2 , and is fitted to a rod  27  guided by frame  19  and activated by a cam device not shown. Lateral walls  22  and  23  are mounted to rotate about respective axes  28  and  29 , are activated by respective cam devices not shown, are located on opposite sides of bottom wall  21 , and are movable between a rest position, and a work position in which they are parallel to each other and to axis A 2 . Jaw  24  is located on the wall  22  side, and rotates about an axis  30  coincident with axis  28 . Wall  22  is defined by a thin, flat plate, and jaw  24  is movable between a rest position, and a work position in which it is parallel to walls  22  and  23  and adjacent to wall  22 . 
     With reference to FIG. 9, plates  25  and respective arms  26  rotate, with respect to frame  19  and about respective axes  31  perpendicular to axes  28 ,  29  and  30 , between a rest position, shown by the dash line, and a work position, shown by the continuous line. 
     With reference to FIG. 1, folding device  8  is fitted to structure S, and comprises a plate  32  mounted to rotate about an axis  33  perpendicular to the FIG. 1 plane. Plate  32  comprises a curved portion  34 ; and a flat portion  35  having slots  36  for the insertion of part of device  9 . Curved portion  34  and flat portion  35  have respective faces  37  and  38  connected to each other and facing wheel  5 . 
     Device  9  comprises a wheel  39  shown by the dash line in FIG. 1, and which rotates, with respect to structure S, about an axis  40  parallel to axis  33 . Wheel  39  comprises three folding devices  41  equally spaced about axis  40  and having plates  42  which, in use, engage slots  36  comb-fashion and project from face  38 . 
     With reference to FIG. 2, each lateral wall  13  of pocket  6  comprises an inner face  43  directly contacting group  3  in use, an outer face  44 , and a free end  45 ; bottom wall  12  of pocket  6  comprises a face  46  contacting a central portion of group  3  in use; wall  22  comprises an inner face  47  and an outer face  48 ; wall  23  comprises an inner face  49 ; jaw  24  comprises an inner face  50 ; and bottom wall  21  of pocket  7  comprises a face  51 . 
     With reference to FIG. 9, each plate  25  comprises an inner face  52  contacting the ends of cigarettes  2  in group  3  in use; an outer face  53 ; and two opposite ends  54  and  55  (FIG.  10 ). 
     In actual use, wheels  4 ,  5  and  39  rotate continuously, wheel  5  clockwise and wheels  4  and  39  anticlockwise in FIG.  1 . As wheels  4  and  5  rotate, pockets  6  and  7  are swung about respective axes  11  and  20  by cam devices (not shown) known in the automation industry and comprising pawls, levers, and cam profiles (not shown) for moving pockets  6  and  7  into given positions with respect to wheels  4  and  5  along respective paths P 1  and P 2 . The movements of lateral walls  22  and  23 , jaw  24 , bottom walls  12  and  21 , plate  32 , and folding devices  41  are controlled by similar cam devices also operated by rotation of wheels  4  and  5 . Pockets  6  and  7  are fed continuously along respective paths P 1  and P 2 , and are so timed and swung about respective axes  11  and  20  as to align axes A 1  and A 2  and insert pocket  6  inside pocket  7  along the common portion T of paths P 1  and P 2 . As wheel  4  rotates, and upstream from portion T, gripper  17  grips a sheet  18  of wrapping material supplied in known manner not shown, and retains sheet  18  of wrapping material in a given position with respect to pocket  6 . 
     With reference to FIG. 2, axes A 1  and A 2  are aligned, and bottom wall  21  is moved along axis A 2  from the position shown by the dash line to the position shown by the continuous line, in which sheet  18  of wrapping material is gripped between face  51  of bottom wall  21  and ends  45  of walls  13 . At this stage, gripper  17  releases sheet  18  of wrapping material, which has a portion  56  compressed between ends  45  of the two lateral walls  13  of pocket  6 , and two flaps  57  and  58  projecting on opposite sides of portion  56 . 
     In FIG. 2, walls  22  and  23  are open to enable pocket  6  to be inserted easily inside pocket  7 . 
     As wheels  4  and  5  travel further along portion T, pocket  6  is inserted inside pocket  7 . At this stage, bottom wall  21  is withdrawn along axis A 2 , and pocket  6  penetrates pocket  7  to fold flaps  57  and  58 , with respect to portion  56 , about ends  45  of walls  13  of pocket  6 . In the meantime, lateral walls  22  and  23  are closed, i.e. positioned parallel to each other, so that flaps  57  and  58  are folded squarely with respect to portion  56 . 
     With reference to FIG. 4, the fold between portion  56  and flap  57  is made about end  45  of wall  13 , and, being short, flap  57  is gripped completely between outer face  44  of wall  13  and inner face  47  of wall  22 . With reference to FIGS. 3 and 5, the fold between portion  56  and flap  58  is made about end  45  of the other wall  13 , and, being long, flap  58  is gripped partly between outer face  44  of wall  13  and inner face  49  of wall  23 , and projects partly from pocket  7  to define a flap  59 . 
     With reference to FIG. 6, as wheels  4  and  5  rotate, pockets  6  and  7  are gradually parted, so that lateral walls  13  are extracted from pocket  7 . At this stage, pockets  6  and  7  swing about respective axes  11  and  20  to keep axes A 1  and A 2  aligned, and bottom wall  12  is gradually extracted from lateral walls  13  by cam device  16 , and exerts pressure on the group and on sheet  18  of wrapping material to retain group  3  inside pocket  7  and prevent sheet  18  of wrapping material from slipping when extracting lateral walls  13  from pocket  7 . With reference to FIGS. 9 and 10, once lateral walls  13  are extracted from pocket  7 , plates  25  are moved into the work position, in which inner faces  52  of plates  25  rest on opposite ends of group  3  on opposite sides of bottom wall  12 . In other words, faces  52  of plates  25  are coplanar with and adjacent to face  46  of bottom wall  12 . Once plates  25  are moved into the work position, bottom wall  12  is withdrawn along axis A 1 , and group  3  and sheet  18  of wrapping material are retained firmly inside pocket  7  by plates  25 . 
     Extracting lateral walls  13  from pocket  7  before moving plates  25  into the work position enables plates  25  to be so sized as to form, with wall  23 , an extremely small passage, which extends between end  54  and face  49  of wall  23 , only allows the passage of sheet  18  of wrapping material, and through which flap  59  projects (FIG.  8 ). 
     Pockets  6  and  7  are then fed along respective paths P 1  and P 2  and parted. Pocket  7  fed along path P 2  is brought into contact with plate  32 , and flap  59  is gripped partly between face  37  and ends  54  of plates  25 , and is folded into an L about ends  54 . As wheel  5  rotates further, pocket  7  is fed along flat portion  35  of plate  32 , as shown in FIG. 7, where flap  59  is smoothed between flat face  38  and outer faces  53  of plates  25 . To slide pocket  7  along plate  32 , pocket  7  and plate  32  are swung about respective axes  20  and  33  to keep plates  25  parallel to flat face  38 , and to grip flap  59  partly between faces  53  of plates  25  and face  38  of plate  32 . 
     Once flap  59  is folded about ends  54 , sheet  18  of wrapping material has a flap  60  projecting from pocket  7 . With reference to FIG. 11, as pocket  7  slides along flat face  38  (not shown in FIG. 11 for the sake of clarity), a plate  42  engages slots  36  comb-fashion and folds flap  60  onto outer face  48  of lateral wall  22 , and about the end  22   a  of lateral wall  22  as shown in FIG.  12 . Once the tubular wrapping is formed and plate  42  extracted from slots  36 , jaw  24  is closed to retain flap  60  between outer face  48  of wall  22  and inner face  50  of jaw  24 . 
     Once the tubular wrapping is completed and kept closed by jaw  24 , plates  25  can be extracted and restored to the rest position, and the tubular wrapping is then closed at the ends in known manner (not shown) to form a closed wrapping. Though both the tubular wrapping and the closed wrapping have flap  57  and flap  60  separated by wall  22 , this in no way impairs extraction of the wrapping from pocket  7 , which is done by simply opening jaw  24  and activating bottom wall  21  to slide flaps  57  and  60  with respect to wall  22  and expel the wrapped group  3 . Once the wrapping is extracted from pocket  7 , flaps  57  and  60  overlap. Of the advantages of the wrapping method described, it should be pointed out that, besides preventing slippage of sheet  18  of wrapping material, it also enables the formation of sharp-edged folds, which are particularly appreciated in the wrapping of cigarettes.