Abstract:
A method and device for finishing cellophane-wrapped packets, whereby a succession of stacks, each defined by two superimposed packets having respective heat-shrink overwrappings, are fed successively by a conveyor wheel along a circular track extending through an unloading station, prior to reaching which the packets in each stack are parted in an axial direction with respect to the conveyor wheel, and are then fed, in a radial direction with respect to the conveyor wheel, along respective superimposed paths separated by a heating plate.

Description:
This application claims priority to Italian Application No. BO2004A 000137 filed on Mar. 11, 2004 in the name of G. D SOCIETA&#39; PER AZIONI. 
   The present invention relates to a method and device for finishing cellophane-wrapped packets having respective overwrappings of heat-shrink material. 
   Though suitable for finishing any type of packet having an overwrapping of heat-shrink material, the present invention may be used to advantage in the tobacco industry for finishing packets of cigarettes coming off a cellophaning machine, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   In the tobacco industry, cellophaning machines are used, which are capable of forming the packets into stacks, each defined by a first and a second packet, with the second packet superimposed on the first, and with a major lateral surface of the second packet contacting a corresponding major lateral surface of the first packet. The stacks of packets are normally fed successively in a given direction along a track extending in a plane parallel to said major lateral surfaces, and through an unloading station where the stacks are unloaded onto an unloading conveyor and fed to an input of a cartoning machine. 
   The packets coming off cellophaning machines are normally subjected to a finish operation, in which the packets are heated to heat-shrink the overwrappings. For this to be done properly, without wrinkling the overwrappings, both the major lateral surfaces of each cellophane-wrapped packet must be heated, which is relatively easy to do on cellophaning machines on which the packets are conveyed one by one. The same does not apply, however, on cellophaning machines of the type described above, on which the packets are conveyed stacked in pairs, on account of the mutually contacting major lateral surfaces of the packets in each stack not being accessible directly. 
   U.S. Pat. No. 6,511,405B1 discloses an apparatus for producing cigarette packs of the hinge-lid-box type; in order to improve the outer appearance of the cigarette packs, once an outer wrapper has been provided and sealed the cigarette packs are conveyed through a shrinking station and subjected to the action of heat in the region of the large-surface-area pack sides, in particular in the region of upwardly directed front sides. For this purpose, heating plates are positioned in the region of the shrinking station and transmit heat to the upwardly directed surfaces of the cigarette packs. 
   U.S. Pat. No. 5,462,401A1 discloses a method of separating two superimposed rows of cigarette packets originally in direct contact with each other, whereby the two superimposed rows are fed into the input station of a separating device in a first direction parallel to the longitudinal axis of the rows; and are fed in a second direction, perpendicular to the first direction, to a separating station where they are separated by raising the top row and subsequently inserting, between the separated rows, a separating plate which is maintained between the rows as these are removed from the separating station in a third direction parallel to the first. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method and device of finishing cellophane-wrapped packets having respective overwrappings of heat-shrink material, which provides, in a straightforward, low-cost manner, for directly heating both the major lateral surfaces of each packet on cellophaning machines on which the packets are conveyed stacked in pairs. 
   According to the present invention, there is provided a method and a device of finishing cellophane-wrapped packets having respective overwrappings of heat-shrink material as recited in the attached claims. 

   
     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 partial plan view of a preferred embodiment of the device according to the present invention; 
       FIGS. 2 ,  3  and  4  are similar to  FIG. 1 , and show the  FIG. 1  device in respective operating positions; 
       FIG. 5  shows a section along line V—V in  FIG. 2 ; 
       FIG. 6  shows a section along line VI—VI in  FIG. 3 ; 
       FIG. 7  shows a section along line VII—VII in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIGS. 1 to 4  indicates as a whole a device for finishing cellophane-wrapped packets  2  ( FIGS. 2 to 4 ) having respective overwrappings  3  of heat-shrink material. 
   Device  1  comprises a conveyor wheel  4  mounted to rotate in steps about a vertical axis  5 , and comprising a number of peripheral pockets  6  equally spaced about axis  5  and for receiving respective stacks  7  ( FIGS. 2 to 4 ), each defined, as shown more clearly in  FIGS. 5 to 7 , by a bottom packet  2   a  and a top packet  2   b  positioned contacting each other along respective major lateral surfaces  8   a ,  8   b  facing upwards and downwards respectively. 
   Conveyor wheel  4  rotates anticlockwise in  FIGS. 1 to 4  to feed stacks  7  successively in a travelling direction  9  along a track  10  bounded externally by a cylindrical retaining wall  11 , which is coaxial with axis  5 , is located outwards of pockets  6 , and extends upwards from a flat, horizontal surface  12  defining a bottom surface of conveyor wheel  4 , defining the bottom of pockets  6 , and supporting bottom packets  2   a  of stacks  7 . 
   Track  10  extends through an unloading station  13 , immediately upstream from which, cylindrical wall  11  comprises a lower portion  11   a , the height of which above surface  12  is approximately equal to but no less than the thickness of a packet  2 . At unloading station  13 , lower portion  11   a  is broken by a radial opening  14  of a width at least equal to the length of a packet  2 , and which connects track  10  to an unloading conveyor  15  which receives stacks  7  successively in an unloading direction  16  substantially parallel to surface  12 , directed radially with respect to conveyor wheel  4 , and crosswise to travelling direction  9  at unloading station  13 . 
   As shown more clearly in  FIGS. 6 and 7 , unloading conveyor  15  comprises two endless belts  17  and  18  looped about respective horizontal pulleys  19  (only one of which is shown for each endless belt  17 ,  18 ) and having respective conveying branches  20  and  21 , which are positioned facing one over the other, are fitted with respective heating elements  22 , and are both moved in the same direction parallel to unloading direction  16 . Conveying branch  20  is located beneath conveying branch  21 , is substantially coplanar with track  10 , and is separated from conveying branch  21  by a heating plate  23 , which is parallel to track  10  and to conveying branches  20  and  21 , is positioned symmetrically with respect to conveying branches  20  and  21 , and defines, between conveying branches  20  and  21 , two unloading paths or channels  24  and  25  of equal height and each of a height substantially equal to the thickness of a packet  2 . 
   Device  1  also comprises a spacer assembly  26  for parting major lateral surfaces  8   a ,  8   b  of packets  2   a ,  2   b  of each stack  7  immediately upstream from unloading station  13 ; and a push device  27  movable back and forth in unloading direction  16  to feed each packet  2   a ,  2   b  of each stack  7  along respective unloading channel  24 ,  25  at unloading station  13 . 
   Spacing assembly  26  comprises a lateral push member  28  for moving packet  2   b  of each stack  7  with respect to relative packet  2   a , by applying thrust to packet  2   b  in a direction crosswise to travelling direction  9  and substantially parallel to surface  12 , to move packet  2   b  outwards and away from axis  5 , so that a portion of major lateral surface  8   b  of packet  2   b  projects laterally outwards of conveyor wheel  4  with respect to major lateral surface  8   a  of relative packet  2   a . Spacing assembly  26  also comprises a bottom push member  29  for applying thrust to the projecting portion of major lateral surface  8   b  in a lift direction substantially perpendicular to surface  12  and parallel to axis  5 . 
   Lateral push member  28  and bottom push member  29  are passive members located in fixed positions along track  10  and extending partly upstream from and partly through unloading station  13 . More specifically, lateral push member  28  is defined by a plate  30 , which is mounted facing track  10 , is parallel to surface  12 , is located on the opposite side of track  10  to unloading channels  24  and  25 , and is separated from surface  12  by a distance greater than the thickness of a packet  2  and smaller than the height of a stack  7 . On the side facing lower portion  11   a  of cylindrical wall  11 , plate  30  comprises a curved cam profile  31 , an inlet portion of which is separated from axis  5  by a distance equal to the distance between axis  5  and the back of each pocket  6 , and an outlet portion of which, extending in front of lower portion  11   a  and through unloading station  13 , is separated from axis  5  by a distance greater than the distance between axis  5  and the back of each pocket  6 . 
   Immediately upstream from unloading station  13 , bottom push member  29  comprises a wedge-shaped plate  32 , which is sickle-shaped when viewed from above, is located over lower portion  11   a  of cylindrical wall  11 , is substantially coplanar with heating plate  23 , and projects partly over track  10 . Plate  32  faces cam profile  31 , and projects towards cam profile  31  from a block which is bounded, on the side facing track  10 , by a curved surface  31   a  parallel to cam profile  31  and separated from cam profile  31  by a distance substantially equal to the width of track  10 . Plate  32  is bounded at the bottom by a flat surface  33  facing and parallel to surface  12 , and is bounded at the top by a sloping two-slope surface  34 , so that plate  32  increases in thickness towards unloading station  13  in travelling direction  9 , and decreases in thickness towards track  10  in unloading direction  16 . From a width of substantially zero, plate  32  increases in width towards unloading station  13 , and is connected at unloading station  13  to a flat plate  35 , which forms part of bottom push member  29 , extends substantially the whole width of track  10 , and is bounded at the bottom by a flat surface coplanar with surface  33  and defining, with surface  12 , a passage  36  engaged by packets  2   a.    
   Push device  27  is located at unloading station  13 , moves back and forth across track  10  in unloading direction  16 , and comprises, on its free end, a fork  37 , in turn comprising two arms  38  and  39  of the same length, located one over the other, and parallel to unloading direction  16 . Arm  38  is located beneath arm  39  and plate  35  and above surface  12 , and moves through passage  36  to engage a stationary packet  2   a  at unloading station  13  and push it in unloading direction  16  to the inlet of unloading channel  24 ; while arm  39  is located above plate  35 , and engages a stationary packet  2   b  at unloading station  13  to push it in unloading direction  16  to the inlet of unloading channel  25 . 
   To feed each packet  2   b  to the inlet of unloading channel  25  and onto heating plate  23 , plate  35  is connected to heating plate  23  by an intermediate plate  40 , the bottom surface of which is coplanar with the bottom surface of plate  35 , and the top surface of which slopes upwards towards heating plate  23 , which is thicker than plate  35 . 
   Operation of device  1  will be described with reference to the accompanying drawings, with reference to one stack  7 , and as of the instant ( FIG. 2 ) in which stack  7  (the first bottom-left stack  7  in  FIG. 2 ) reaches a position immediately upstream from spacing assembly  26 . 
   As the stack  7  considered engages spacing assembly  26  ( FIG. 5  and top stack  7  in  FIG. 2 ), packet  2   b  laterally contacts cam profile  31 , is moved gradually outwards with respect to conveyor wheel  4 , and slides on top of relative packet  2   a  to project partly from relative pocket  6 . As a consequence of this substantially radial movement with respect to conveyor wheel  4 , a portion of major lateral surface  8   b  of packet  2   b  moves onto plate  32 , and packet  2   b , as it moves gradually towards unloading station  13 , is raised with respect to relative packet  2   a  and eventually fed onto plate  35 . During this movement, packet  2   a  continues along track  10 , remains housed entirely inside relative pocket  6 , and engages passage  36 . 
   At unloading station  13  ( FIG. 6  and top stack  7  in  FIG. 3 ), packet  2   a  is located beneath plate  35  and still in its original position inside relative pocket  6 , while packet  2   b  is located over plate  35  and partly extracted from relative pocket  6 . 
   At this point, when push device  27 , in the normal withdrawn position shown in  FIG. 6 , is activated ( FIGS. 4 and 7 ), arm  38  first contacts packet  2   a  and moves packet  2   a  only in direction  16  into a position directly beneath relative packet  2   b , after which, both packets  2   a  and  2   b  are moved simultaneously along relative unloading channels  24  and  25  into a final position ( FIGS. 4 and 7 ) in which both packets  2   a  and  2   b  engage unloading conveyor  15  and are positioned with major lateral surfaces  8   a  and  8   b  directly contacting heating plate  23 . 
   In other words, each packet  2   a ,  2   b  travels along unloading conveyor  15  with its two major lateral surfaces exposed to the heat produced by heating plate  23  and relative heating element  22  respectively, thus evenly shrinking relative overwrapping  3 . 
   In connection with the above, it should be pointed out that this is achieved using a fully passive spacing assembly  26 , i.e. comprising fixed, non-powered members, which involve practically no mechanical complications, and in no way affect the reliability of conveyor wheel  4 .