Patent Publication Number: US-6901721-B2

Title: Unit for overwrapping packets

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a unit for overwrapping packets. 
   The invention finds application to advantage in the manufacture of tobacco products, relating as it does to the operation of overwrapping packets that contain such products, and in particular packets of cigarettes, to which reference is made explicitly throughout the following specification albeit with no limitation in general scope implied. 
   More particularly, the present invention relates to a unit for overwrapping packets substantially of rectangular prismatic geometry, delimited axially by two opposite end faces, and delimited laterally by two larger side faces and by two smaller side faces extending parallel to a longitudinal axis of the rectangular prism. The packets are overwrapped as they advance in a predetermined direction along a predetermined wrapping path. 
   Such units generally include feed devices serving to advance leaves of overwrapping material obtained by cutting a continuous strip of the material as it decoils from a relative roll. 
   Modern packaging machines are capable of notably high operating speeds, especially continuous motion cigarette packers of which the overwrapping units in question form a part. To ensure that products will emerge faultlessly overwrapped, therefore, it becomes more and more important that the leaves of overwrapping material remain under continuous and complete control as they are advanced by the feed devices, in order to avoid any kind of problem that could derive from incorrect positioning and loss of timing, causing the leaf to be applied defectively to the packet and producing an overwrap spoiled by unsightly creases or similar flaws. 
   The object of the present invention is to provide a unit for overwrapping packets such as will be able to fulfil the requirements mentioned above when operating at the high production tempo typical of a modern packaging machine. 
   SUMMARY OF THE INVENTION 
   The stated object is realized according to the invention in a unit for overwrapping packets, comprising a unit by which packets are transferred through an assembly station and there united with leaves of wrapping material, then toward a folding station where the selfsame leaves are bent around the packets, also feed means by which the leaves are caused to advance along a first path extending between a cutter device and the assembly station. 
   To advantage, the feed means are embodied as a conveyor set in motion continuously along the first path while restraining the leaves advanced along the selfsame path, and the transfer unit comprises a plurality of carriers supporting the packets, each equipped with means by which to grip one end of a leaf adhering to the conveyor and detach it progressively from the selfsame conveyor before effecting an initial overwrapping step of folding the leaf partly around a relative packet. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in detail, by way of example, with the aid of the accompanying drawings, in which: 
       FIGS. 1  to  4  show a first preferred embodiment of the unit for overwrapping packets according to the invention, illustrated schematically in a side elevation with certain parts omitted and seen in a succession of operating steps; 
       FIG. 5  shows a packet of cigarettes, illustrated schematically and in perspective, overwrappable by the unit of  FIG. 1 ; 
       FIG. 6  shows a second preferred embodiment of the unit for overwrapping packets according to the invention, alternative to the first, illustrated schematically in a side elevation with certain parts omitted and seen in the same operating step as that of  FIG. 3 ; 
       FIG. 7  is an enlarged detail of the overwrapping unit illustrated in  FIGS. 1  to  4  and in  FIG. 6 , viewed schematically in perspective. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 1  to  4  of the drawings,  1  denotes a portion of an overwrapping machine or cellophaner equipped with a unit  2  for overwrapping packets  3  of rectangular parallelepiped appearance, as illustrated in  FIG. 5 , each referable to a longitudinal axis  4  and presenting two mutually parallel larger side faces  5  parallel also with the longitudinal axis  4  and with a transverse axis  6 , two mutually parallel smaller side faces  7  parallel also with the longitudinal axis  4 , and two mutually parallel end faces  8  normal to the longitudinal axis  4 . 
   The overwrapping unit  2  comprises a unit  9  by which the packets  3  are transferred through an assembly station  10  where a leaf  11  of wrapping material (normally polypropylene) is associated with each successive packet  3 . The leaves  11  of material are directed into the station  10  from a conveyor  12 , operating in conjunction with a pair of pinch rolls  13 , by which a continuous strip  14  of the wrapping material is decoiled from a bulk roll (not illustrated), the single leaves  11  being generated by a cutter device  15  associated with the conveyor  12  and then carried along a first path  16  by the selfsame conveyor  12  toward the assembly station  10 . 
   More exactly, as illustrated in  FIGS. 1  to  4  and  FIG. 7 , the conveyor  12  consists in a suction roller  17  rotatable continuously about a respective axis  17   a  in a clockwise direction, denoted F 1  in the drawings. The roller  17  presents a cylindrical surface  18  of revolution designed to retain both the leading end of the continuous strip  14  and the leaves  11  separated from the selfsame strip by the cutter device  15 , which comprises an outer blade  19  positioned to interact with two strikers  20  mounted to the roller  17  in positions angularly equidistant one from the other. The same cylindrical surface  18  affords a plurality of radial holes  21  connected by way of conventional means to a source of negative pressure not illustrated in the drawings. 
   The transfer unit  9  comprises a folder wheel  22  driven continuously about an axis  22   a  disposed parallel to the axis  17   a  of the suction roller  17 , rotating in a counterclockwise direction denoted F 2  in the drawings. The wheel  22  is equipped with a plurality of carriers  23  equispaced angularly about the periphery, each serving to support a respective packet  3  and comprising a block  24  of U-profiled section, mounted pivotably to a respective shaft  25  anchored to the folder wheel  22  with its axis  25   a  parallel to the axis  22   a  of the selfsame wheel  22 . 
   Each block  24  is furnished, internally, with a rigidly associated gripper  26  designed to receive a single packet  3 , comprising two pivotably anchored jaws  27  rotatable about corresponding axes parallel to the axis  25   a  of the shaft  25 , and externally, mounted to one of the two members of the U-profile, with means  28  by which to grip one end  11   a  of the leaf  11  of wrapping material held by the suction roller  17 . Such gripping means  28  comprise a first movable jaw  29  hingedly associated with a pivot  30  disposed parallel to the axis  25   a  of the shaft  25 , and a second fixed jaw  31  fastened directly to the corresponding member of the block  24 , against which the first jaw locates. 
   Each block  24  can be made to pivot back and forth about the respective axis  25   a  through the agency of conventional actuator means (not indicated) acting directly on the corresponding shaft  25 , whilst the folder wheel  22  also carries the selfsame blocks  24  along a second path  32  passing through the assembly station  10  substantially tangential to the first path  16 . 
   During its progress along the second path  32 , in particular, and within the dimensional compass of the overwrapping unit  2 , each carrier  23  is capable of movement between two limit positions, of which a first coincides both with a position denoted  33 , enabling the admission of a packet  3  at an entry station  33   a  into which successive packets  3  are directed by a feed device  34 , shown schematically in  FIGS. 1  to  4  as a block, such as will insert the packet  3  sideways-on between the jaws  27  of the gripper  26 , and with a position denoted  35  in which the leaf  11  of material is bent partially around the packet  3  at a folding station  35   a . In these two positions  33  and  35 , both representing the first limit position, the jaws  27  extend substantially in a radial direction relative to the folder wheel  22 , so that during the step of inserting the packet  3  between the jaws  27 , which will be spread apart, the packet  3  can be translated parallel with its transverse axis  6  to the point at which one smaller side face  7  enters into contact with a locating surface  36  interposed between the jaws  27 , assuming a position of maximum radial projection from the wheel  22 . 
   The second of the two limit positions is assumed by the carrier  23  during its passage through the assembly station  10  and produces a configuration, for reasons that will become clear, in which the advancing packet  3  assumes a position of minimum radial projection from the wheel  22 . 
   As illustrated in  FIGS. 1  to  4  and in  FIG. 6 , the overwrapping unit further comprises stationary folder and guide means  37  positioned downstream of the assembly station  10 , considered in relation to the direction of rotation F 2  of the wheel  22 , along which the folding position  35  is assumed by the carrier  23 . In particular, the stationary folder and guide means  37  comprise a fixed restraint  38  extending concentrically with the axis  22   a  of the folder wheel  22  from a position immediately beyond the assembly station  10  to a transfer station of conventional embodiment, not illustrated, where the packets  3  and the relative leaves  11  are released. 
   More particularly, the side of the restraint  38  directed toward the folder wheel  22  presents an aspirating surface  39  fashioned with a plurality of uniformly distributed suction holes  40  such as will attract each advancing leaf  11  of wrapping material and smooth it over the corresponding smaller side face  7  of the relative packet  3 . 
   It will be observed, with reference in particular to  FIGS. 2 ,  3  and  7 , that the cylindrical outer surface  18  of the suction roller  17  presents two angularly equidistant openings  41  serving to admit and afford a passage to the movable jaw  29  of the gripping means  28 . More exactly, each opening  41  appears as a plurality of grooves  42  formed in the cylindrical surface  18  of the roller  17  in such a way as to create a relative plurality of intercalated sectors  43 , each presenting a given number of the aforementioned suction holes  21  on its cylindrical surface. The roller  17  is timed in such a manner that the leading end  11   a  of each leaf  11  will be positioned over and retained by the sectors  43  of a relative opening  41 , in readiness to be taken up by the gripping means  28 . 
   In particular, the movable jaw  29  of the gripping means  28  appears as a pallet and is furnished with a plurality of fingers  44  which on arrival at the assembly station  10  are able to locate in and pass along the grooves  42  in such a way as to detach the leading end  11   a  of the leaf  11  from the sectors  43  and pin it against the fixed jaw  31 . 
   In operation, with the folder wheel  22  moving in the conveying direction F 2  about its axis  22   a  of rotation, each carrier  23  is brought into alignment with the entry position  33  (FIG.  1 ), whereupon a packet  3  is directed by the feed device  34  against the locating surface  36  and between the jaws  27 , which close against the larger side faces  5  of the packet  3  to apply the gripping action. Proceeding along the second path  32  and through an arc that extends from the entry station  33  to the folding position  35 , each carrier  23  will pivot about the relative axis  25   a  first in a direction F 3  contrary to the direction of rotation F 2  of the wheel  22 , to the point at which the packet  3  assumes a position of minimum radial projection. In this position, the packet  3  is disposed with its transverse axis  6  substantially tangential to the periphery of the wheel  22  (FIG.  1 ). The position of minimum radial projection is maintained during the passage of the carrier  23  through the assembly station  10  and for the duration of the step whereby the end  11   a  of the leaf  11  of material is pinned by the movable jaw  29  against the fixed jaw  31 , in the manner described above and illustrated sequentially in  FIGS. 2 ,  3  and  4 , so that the packet  3  makes no contact with the roller  17  when passing through and beyond the station  10 . 
   Once past the assembly station  10 , as discernible in particular from  FIGS. 3 and 4 , the carrier  23  is made to pivot in a direction F 4  convergent with the direction of rotation F 2  of the wheel  22 , so that by the time the folding position  35  has been assumed, the advancing packet  3  will have returned to its position of maximum radial projection from the wheel  22 , in this instance with the outwardly directed smaller side face  7  offered substantially in contact to the aspirating surface  39  of the restraint  38 . 
   Observing the sequence of steps illustrated in  FIGS. 1  to  4 , it will be seen that the end  11   a  of each leaf  11  continues to be held throughout the steps of being taken up and detached progressively from the surface  18  of the suction roller  17 , and during its passage toward the folding position  35 . Moreover, the position of the leaf  11  is controlled first by the roller  17  and subsequently, during its gradual separation from the cylindrical surface  18 , by the initial stretch of the aspirating surface  39  of the restraint  38  as indicated in  FIG. 2 , which shows an intermediate portion of the leaf  11  held by this same stretch of the aspirating surface  39 , while the trailing end  11   b  of the leaf  11  opposite to the gripped leading end  11   a  is still retained by the surface  18  of the suction roller  17 . 
   As the folder wheel  22  continues rotating on its axis  22   a  and the carrier  23  continues to pivot in the direction denoted F 4  about the axis  25   a  of the respective shaft  25 , the trailing end  11   b  of the leaf  11  detaches from the surface  18  of the suction roller  17  but will be taken up immediately onto the aspirating surface  39  of the shroud  38 , along which it then slides ( FIGS. 3 and 4 ) until in alignment with the folding position  35 , as illustrated in  FIG. 1 , thence toward the aforementioned release and transfer station (not illustrated). 
   As discernible from  FIGS. 1 ,  2  and  3 , and from  FIG. 7 , the peripheral velocity of the suction roller  17  is faster than the decoil rate imposed by the pinch rolls  13 , so that each leaf  11  separated by the cutter will be distanced from the leading edge of the continuous strip  14 , which continues to cling to the roller  17  but is forced to slip on the relative surface  18 . 
   In the example of  FIG. 6 , the suction roller  17  comprises a hub  45  rotatable about the relative axis  17   a  and presenting two angularly equidistant bosses  46  serving both as support elements for the aforementioned strikers  20 , and as mountings for relative pivots  47  disposed parallel to the roller axis  17   a  and supporting two semicircular sectors  48  that combine to make up the cylindrical surface  18  of the suction roller  17 . 
   The two pivots  47 , are connected mechanically to actuator means  49 , represented schematically by a block, such as will cause each sector  48  to rock on the relative pivot  47  between an at-rest position, concentric with the roller axis  17   a,  and an open position assumed when passing through the assembly station  10  in such a way as to bring the leading end  11   a  of the leaf  11  substantially into contact with the gripping means  28 , of which the jaws  29  and  31  operate in the manner already indicated, the two sectors  48  being furnished both with suction holes  21  and with openings  41  as in the case of the embodiment described above. It will be appreciated that the suction holes  21  can be connected to the source of negative pressure (not illustrated) by way of flexible pipelines (not illustrated) such as will allow the sectors  48  to assume the two limit positions unhindered, or alternatively, by way of ducts routed through the pivots  47 .