Abstract:
A device for splicing strips has a first drum rotating about a first axis and having a first outer face for selectively retaining and guiding a first strip; and a second drum rotating about a second axis and having a second outer face for selectively guiding and retaining a second strip; the first and second outer face are so shaped as to form a gap for passage of the strips, and to press the first and second strip and a sticker together as a function of the indexing angles of the first and second drum.

Description:
The present invention relates to a strip splicing device. 
   More specifically, the present invention relates to a strip splicing device for a cigarette packing machine, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   Modern cigarette packing machines operate at extremely high speed, and so consume enormous amounts of packing material, which, when possible, is supplied off reels of strip material, from which sheets of packing material are cut to size. In view of the large amount of packing material consumed, run-out reels must be replaced with new ones, and the respective strips spliced, to ensure continuous supply of the sheets of packing material without stopping the machine. Modern packing machines are therefore equipped with two pins for supporting respective reels; and a device for splicing the strips of the respective reels. Splicing devices provide for joining the end of a new reel strip to a run-out reel strip, and for cutting the run-out reel strip downstream from the splice. The drawbacks of known splicing devices are substantially due to their complexity and, therefore, unreliability. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a splicing device which is straightforward in design, compact, and extremely reliable. 
   According to the present invention, there is provided a splicing device for splicing a first strip fed off a first reel, and a second strip fed off a second reel; the device being characterized by comprising a first drum rotating about a first axis and having a first face for selectively retaining and guiding the first strip; and a second drum rotating about a second axis and having a second face for selectively guiding and retaining the second strip; the first and second face being so shaped as to form a gap between said first and said second face, and to selectively press the first and second strip together as a function of given indexing angles of the first and second drum. 
   The first and second drum provide for retaining, guiding, and splicing the strips, and so obtaining a device which is straightforward, compact and reliable. 
   The present invention also relates to a strip splicing method. 
   According to the present invention, there is provided a method of splicing a first strip fed off a first reel, and a second strip fed off a second reel; the second strip having a sticker on its free end; and the method being characterized by guiding the first strip along a first face of a first drum, and retaining said free end of the second strip by means of a second face of a second drum and the sticker on the second face of the second drum; and rotating the first and the second drum about a first and a second axis respectively, to press the first and the second strip and the sticker together and so splice the first and the second strip. 

   
     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 side view, with parts in section and parts removed for clarity, of a strip feed unit featuring the splicing device according to the present invention; 
       FIGS. 2 and 3  show side views, with parts in section and parts removed for clarity, of mechanisms of the  FIG. 1  device; 
       FIGS. 4 and 5  show side views, with parts in section and parts removed for clarity, of the  FIG. 1  device in two different configurations; 
       FIGS. 6 and 7  show larger-scale side views of two details of  FIGS. 1 and 4  respectively; 
       FIGS. 8 and 9  show partly sectioned, larger-scale views in perspective of two details of the  FIG. 1  device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a unit for feeding strips to a packing machine (not shown) for producing packets of cigarettes. Unit  1  comprises a frame  2 , which supports two pins  3  and  4 , a splicing device  5 , and two guide pulleys  6  and  7  for respective strips  8  and  9 . Pins  3  and  4  support respective reels  10  and  11 , from which respective strips  8  and  9  are unwound; and pins  3 ,  4  and pulleys  6 ,  7  rotate about respective axes  3   a ,  4   a ,  6   a ,  7   a  parallel to one another and perpendicular to the  FIG. 1  plane. 
   Splicing device  5  is equidistant from pins  3  and  4 , and defines, together with pulley  6 , a portion of the path P 1  of strip  8 , and, together with pulley  7 , a portion of the path P 2  of strip  9  (FIG.  5 ). Splicing device  5  comprises a plate  12  fixed to frame  2  and fitted with two drums  13  and  14  rotating about respective axes  13   a  and  14   a  parallel to axes  3   a  and  4   a ; a cutting tool  15 ; two plates  16  and  17  adjacent to first and second drum  13  and  14  respectively; and a guide pulley  18 , which rotates about an axis  18   a  parallel to axes  13   a  and  14   a , and defines both paths P 1  and P 2 . Unit  1  and device  5  are substantially specularly symmetrical with respect to an axis A. 
   Each drum  13 ,  14  has a cylindrical face  19 ,  20  looped about axis  13   a ,  14   a  and defined by a curved face  21 ,  22  extending about axis  13   a ,  14   a , and by a flat face  23 ,  24  parallel to axis  13   a ,  14   a . The term cylindrical face is used in the sense of a cylinder being any solid defined by generating lines parallel to an axis and distributed along a closed path about the axis. In other words, curved faces  21  and  22  are defined by generating lines parallel to axes  13   a  and  14   a  and distributed along two arcs extending more than 180° about axes  13   a  and  14   a , and flat faces  23  and  24  are defined by generating lines parallel to axes  13   a  and  14   a  and distributed along two chords, which subtend two arcs of less than 180° and complementary to the previous arcs. Consequently, the distance (radius) between axes  13   a ,  14   a  and curved faces  21 ,  22  is greater than the distance (chord distance) between flat faces  23 ,  24  and axes  13   a ,  14   a . In fact, the circular shape of drums  13  and  14  is interrupted by flat faces  23  and  24 , which connect the ends of curved faces  21  and  22 . Drums  13  and  14  also comprise respective suction channels  25  and  26 , which come out along faces  21  and  22 , close to faces  23  and  24 ; and drums  13  and  14  rotate in opposite directions about respective axes  13   a  and  14   a  to assume a first rest position ( FIG. 1 ) and a second rest position (FIG.  5 ), in which they are offset angularly by 180° with respect to a symmetrical position with respect to axis A. That is, both flat faces  23  and  24  are parallel and face upwards in  FIG. 1 , and are parallel and face downwards in FIG.  5 . 
   Plates  16  and  17  have respective concave faces  27  and  28 , which face each other, communicate with respective suction channels  29  and  30 , and have respective ends adjacent to respective drums  13  and  14 . 
   Cutting tool  15  is located along axis of symmetry A, between pins  3 ,  4  and drums  13 ,  14 , and comprises a fixed portion  31  for guiding strips  8  and  9  along a face  32  perpendicular to the  FIG. 1  plane; and a movable assembly  33  movable about an axis  33   a  perpendicular to the  FIG. 1  plane. Face  32 , together with face  21  of face  19  of drum  13 , defines part of path P 1  of strip  8 , and, together with face  22  of face  20  of drum  14 , defines part of path P 2  of strip  9 . Movable assembly  33  comprises two blades  34  and  35 , which are movable between a rest position, not interfering with paths P 1  and P 2 ; a first work position, in which blade  34  interferes with path P 1  to cut strip  8 ; and a second work position, in which blade  35  interferes with path P 2  to cut strip  9 . 
   Drums  13 ,  14  and assembly  33  are rotated about respective axes  13   a ,  14   a ,  33   a  by a single drive member  36  shown schematically in FIG.  2 . Drive member  36 , which is preferably an electric step motor, drives a gear  37 , which rotates about an axis  37   a  and meshes with a gear  38  integral with drum  13  and rotating about axis  13   a . Gear  38  meshes with a gear  39  integral with drum  14  and rotating about axis  14   a.    
   With reference to  FIG. 3 , drum  13  is integral with two cams  40  and  41 , which rotate about axis  13   a , and cooperate with two tappets  42  and  43  on the free ends of a fork  44  integral with movable assembly  33  to swing blades  34  and  35  about axis  33   a  as a function of the position of drums  13  and  14 . 
   In actual use, and with reference to  FIG. 1 , strip  8  is fed off reel  10  and along path P 1  to the packing machine (not shown), which exerts pull on strip  8  to stretch it between reel  10 , pulley  6 , face  32  of cutting tool  15 , curved face  21  of drum  13 , and pulley  18 , to define path P 1  of strip  8 . In other words, strip  8 , drawn by the packing machine (not shown), slides on faces  32  and  21 , and rolls about pulleys  6  and  18 . 
   On the other side of axis A, strip  9  has a free end with a sticker  45  with an adhesive face  46 , as shown more clearly in FIG.  6 . With reference to  FIG. 9 , strip  9  partly rests on concave face  28 , and the end of strip  9  rests on face  22  of face  20  of drum  14 , at suction channel  26 . In this position, adhesive face  46  of sticker  45  faces outwards, as shown clearly in FIG.  6 . 
   With reference to  FIG. 1 , respective flat faces  23  and  24  of drums  13  and  14  are positioned parallel and facing upwards, so that flat face  24  of drum  14  faces and is a given distance from curved face  21 , along which strip  8  runs. In this first rest position of drums  13  and  14 , a gap for the passage of strip  8  is defined between faces  21  and  24 . 
   As reel  10  is about to run out, device  5 , in addition to guiding and supporting strips  8  and  9 , commences the splicing process, which, as shown in  FIGS. 4 and 7 , comprises synchronously rotating drum  14  clockwise and drum  13  anticlockwise by means of drive member  36  and gears  37 ,  38 ,  39  (FIG.  2 ), so that curved faces  21  and  22  face each other and press together strip  8 , strip  9 , and sticker  45 , the adhesive face  46  of which adheres to strip  8  (FIG.  7 ). Rotation of drum  13  also rotates cams  40  and  41 , which swing blades  34  and  35  clockwise in  FIG. 1 , so that blade  34  interferes with path P 1  of strip  8  to cut strip  8 . Further rotation brings drums  13  and  14  into the second rest position (FIG.  5 ), in which flat faces  23  and  24  face downwards. In other words, splicing is effected by simply rotating drums  13  and  14  180° in opposite directions. In the second rest position shown in  FIG. 5 , strip  9  is fed along path P 2  to the packing machine (not shown). Strip  9 , drawn by the packing machine (not shown) runs along curved face  22 , which faces flat face  23  of drum  13  to form a gap for the passage of strip  9 . 
   In the meantime, the run-out reel  10  is changed with a new one, from which a strip  8  is unwound and placed resting on concave face  27 . The free end of strip  8  has a sticker  45  with an adhesive face  46 , and is placed on face  21 , at suction channel  25 , so that splicing device  5  is ready to splice strips  8  and  9  as reel  11  is about to run out. Splicing is effected by further rotating drums  13  and  14  into the first rest position (FIG.  1 ), in the course of which, cams  40  and  41  swing movable assembly  33  in the opposite direction to before to cut strip  9 . 
   Throughout, the rotation direction of drums  13  and  14  is never inverted: drum  13  is always rotated anticlockwise, and drum  14  clockwise. Which functional characteristic depends substantially on the shape of drums  13  and  14 , and provides for simplifying the actuating mechanisms of splicing device  5 .