Abstract:
A machine for packing products having a first packing unit for producing a succession of first packed groups of products and a second packing unit for grouping the first packed groups into second packed groups, each presenting a number of the first packed groups. A flat support serves for supporting the first packed groups and is interposed between the two packing units. A step-conveying device extends over the flat support and has a succession of pockets for receiving respective first packed groups, and provides an output portion whose pockets are detachable from the first packed groups to release the first packed groups on the flat support.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a product packing machine. 
   Though suitable for packing any, in particular substantially parallelepiped-shaped, product, the present invention may be used to advantage in the tobacco industry for packing packets of cigarettes, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   In the tobacco industry, packing lines are normally used comprising a cartoning machine and a boxing machine, and along which packets of cigarettes are packed in two successive steps: a first step in which groups of normally ten packets are formed and enclosed inside a container to form so-called “cartons” on the cartoning machine; and a second step, in which the boxing machine forms a succession of groups of cartons, which are stacked to form a succession of multilayer groups, each of which is enclosed inside a respective box of cardboard or similar. 
   In packing machines of the above type, the cartoning and boxing machines are normally two separate machines, and the cartoning machine is connected to an input of the boxing machine by a carton group forming device, and by a pocket conveyor which feeds the cartons to the group forming device and extends through a carton quality control station and a carton reject station. 
   One of the drawbacks typical of known packing lines of the above type is that, when a carton is rejected at the reject station, a gap, i.e. an empty pocket, is formed along the conveyor connecting the cartoning machine to the boxing machine, and an incomplete group of cartons is formed, and subsequently rejected, on the group forming device on the boxing machine. 
   One solution employed to eliminate this drawback is to form, for example, along the connecting conveyor, a portion along which the cartons are pushed forward to fill any gaps. Alternatively, the cartons in the incomplete groups rejected by the boxing machine are fed back to the transfer conveyor immediately downstream from the reject station, and used to replace the rejected cartons. 
   Both the above known solutions involve using completely separate cartoning and boxing machines, a group forming device, and a relatively long, complex connecting conveyor. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a product packing machine, in particular for packing packets of cigarettes, designed to eliminate the aforementioned drawbacks. 
   According to the present invention, there is provided a product packing machine comprising a first packing unit for producing a succession of first packed groups of products; a second packing unit for grouping the first packed groups into second packed groups, each comprising a number of said first packed groups. A flat support supports said first packed groups and is interposed between said two packing units; and a conveying device extends over said flat support. The conveying device moves in steps, and has a succession of pockets for receiving respective first packed groups; said conveying device comprisings an output portion whose pockets are detachable from the first packed groups to release the first packed groups on the flat support. The said first packed groups are cartons of packets of cigarettes and said first and said second packing units are a cartoning unit and a boxing unit respectively. 

   
     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, partial side view, with parts removed for clarity, of a preferred embodiment of the machine according to the present invention; 
       FIGS. 2 to 5  show successive operating configurations of the  FIG. 1  machine. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a machine for packing packets  2  of cigarettes, and which comprises a cartoning unit  3  for producing cartons  4 , each comprising a relative group  5  of packets  2 ; and a known boxing unit  6  integrated in cartoning unit  3  and connected directly to cartoning unit  3  at a transfer station  7  where orderly groups  8  of cartons  4  from cartoning unit  3  are fed successively to a group-forming device  9  located at the input of boxing machine  6  and for forming groups  8  into further groups  10 , each of which is packed inside a respective box (not shown) and comprises a number of layers, each defined by at least one respective group  8 . 
   Cartoning unit  3  comprises an output conveying device  11  for receiving a succession of cartons  4  and feeding cartons  4  in steps, crosswise to their longitudinal axis and in a direction  12 , to transfer station  7  located at an output end of conveying device  11 . 
   Conveying device  11  comprises a flat support defined by a substantially horizontal base plate  13  for supporting said succession of cartons  4  in sliding manner; and two conveyors  14  and  15  arranged in series in direction  12  and over plate  13 . Conveyor  14  is defined by two side by side belts  16  (only one shown) located a given distance apart and looped about two pulleys; and conveyor  15  is defined by a belt  17  also looped about two pulleys. More specifically, belts  16 , located upstream from belt  17  in direction  12 , are looped about two pulleys  18  and  19 —of which pulley  19  is a drive pulley—mounted to rotate about respective fixed axes  20  and  21  parallel to plate  13  and perpendicular to direction  12 ; and belt  17  is looped about pulley  19  which is therefore common to both conveyors  14  and  15 —between belts  16 , and about a further pulley  22  fitted to a frame  23  and rotating, with respect to frame  23 , about an axis  24  parallel to axes  20  and  21 . 
   Whereas axes  20  and  21 , as stated, are fixed, axis  24  is movable with frame  23 , under the control of an actuator  25  and in a direction  26  substantially perpendicular to base plate  13 , between a lowered position ( FIGS. 1 ,  3 ,  5 ), in which a bottom conveying branch  27  of belt  17  is coplanar with a bottom conveying branch  28  of belts  16 , and a raised position ( FIGS. 2 ,  4 ), in which bottom conveying branch  27  is tilted upwards with respect to base plate  13  as of pulley  19 . 
   Belts  16 ,  17  have respective successions of equally spaced teeth  29 ,  29   a  defining, along bottom branches  28 ,  27  and with base plate  13 , respective successions of pockets  30 ,  31 , each for receiving a respective carton  4 . Teeth  29  and  29   a  are synchronized about pulley  19  so that each pocket  30  is synchronized with a corresponding pocket  31  beneath pulley  19 ; and teeth  29   a  are so numbered as to define, along bottom conveying branch  27  of belt  17 , a number of pockets  31  at least equal to, but normally greater than, the number of cartons  4  in each group  8 . 
   Bottom conveying branch  28  of belts  16  is separated from base plate  13  by a distance just slightly greater than the thickness of cartons  4  measured in direction  26 , and defines, with base plate  13 , a channel  32 , which continues beneath bottom branch  27  of belt  17 , and along which cartons  4  are fed, not by friction with belts  16  and  17 , but solely by the positive thrust exerted by teeth  29  and  29   a.  When belt  17  is in the raised operating position, however, only the tooth—indicated  29   b —on bottom branch  27  of belt  17  closest to pulley  19  is able to interfere with cartons  4 . 
   A known control station  33  for controlling the quality of cartons  4 , and a known reject station for rejecting faulty cartons  4 , are located in series in direction  12  along the portion of channel  32  extending beneath belts  16 . As shown in  FIG. 2 , when a carton  4  is expelled at reject station  34 , a gap  35  corresponding to an empty pocket  30  is formed in the succession of cartons  4  travelling along channel  32 . 
   Boxing unit  6  faces an output end of base plate  13  in direction  12 , and comprises, beneath group-forming device  9 , a lifting device  36  in turn comprising a plate  37 , which is movable, under the control of an actuator  38  and in a substantially vertical direction  39  perpendicular to direction  12 , between a lowered rest position, in which plate  37  is coplanar with and adjacent to base plate  13 , and a raised work position, in which plate  37  is located inside group-forming device  9 . 
   At transfer station  7 , cartoning unit  3  comprises an accelerating device  40  located along base plate  13 , downstream from pulley  19  in direction  12 , and which comprises a fixed guide  41  having an axis  42  parallel to direction  12 , and a powered slide  43  fitted to guide  41  to move along guide  41  between a withdrawn position, in which slide  43  is located beneath bottom conveying branch  27  of belt  17 , and a forward position, in which slide  43  is located downstream from pulley  22  and at the output end of base plate  13 . Slide  43  supports a push member  44  movable with slide  43  along axis  42 , and which is powered to oscillate about axis  42  between a conveying position, in which push member  44  engages the portion of channel  32  beneath bottom conveying branch  27  of belt  17 , and a return position, in which push member  44  is located outside channel  32 . 
   Operation of machine  1  will now be described as of a normal operating condition ( FIG. 1 ), in which cartons  4  are fed in steps by conveying device  11  along base plate  13  to form, downstream from push member  44  in the withdrawn position, and beneath bottom conveying branch  27  of belt  17  in the lowered position, a group  8  defined, in the example shown, by five cartons  4 . 
   At this point, during a stop of conveying device  11 , actuator  25  is operated to move frame  23  and pulley  22  into the raised position and detach teeth  29   a  of conveying branch  27  from cartons  4  in said group  8 , and accelerating device  40  is operated to move push member  44  first about axis  42  into channel  32 , and then along axis  42  in direction  12  to compact cartons  4  in group  8  and feed group  8  ( FIG. 2 ) onto plate  37  of lifting device  36 . 
   When actuator  38  is operated, group  8  is fed into group-forming device  9  to define, in known manner, at least part of a layer in a group  10  being formed. During the latter operation, push member  44  is moved about and along axis  42  back to its original position ( FIG. 3 ), belt  17  is moved back into the lowered position, and conveying device  11  operates once more in steps to form another group  8  on base plate  13 . 
   In the event a faulty carton  4 —indicated  4   a  —has been detected beforehand at control station  33  and rejected at reject station  34 , a gap  35  is formed along bottom conveying branch  28  of belts  16 , and, on reaching belt  17  ( FIG. 3 ), causes belt  17  to be raised ( FIG. 4 ) to detach relative teeth  29   a  from all the cartons  4  beneath bottom conveying branch  27  of belt  17 . The latter cartons  4  therefore remain stationary on base plate  13 , while the following cartons  4  continue to be fed forward in steps by teeth  29  of belts  16  and by tooth  29   b  of bottom conveying branch  27  of belt  17 , thus closing gap  35 . In the example shown ( FIG. 4 ), one idle step of belt  17  is sufficient to close the gap  35  ( FIG. 3 ) formed by rejection of carton  4   a.    
   Once gap  35  is filled, belt  17  can be moved back into the lowered position ( FIG. 5 ) to form another complete group  8  on base plate  13 . 
   In connection with the above, it should be pointed out that, by detaching teeth  29   a  from cartons  4  along channel  32  beneath bottom conveying branch  27  and downstream from push member  44  in the withdrawn position, not only are gaps  35  eliminated, but complete groups  8  are fed at all times by means of accelerating device  40  onto plate  37  of lifting device  36 . This dual function of belt  17  provides for eliminating any reject device for rejecting incomplete groups  8  on boxing unit  6 , for achieving a highly compact conveying device  11  capable of feeding cartons  4  directly from cartoning unit  3  to boxing unit  6 , and for integrating both these units into a single packing machine such as machine  1  described. 
   Though teeth  29   a  are detached from relative cartons  4 , in the example shown, by dividing conveying device  11  into two conveyors  14  and  15 , and by rotating conveyor  15  upwards about axis  21  of pulley  19 , the same result may obviously be achieved differently. For example, in an embodiment not shown, conveying device  11  is defined by one conveyor comprising an outer belt having, instead of conveying teeth, an equal number of transverse slots; and an inner belt having teeth which engage respective slots in the outer belt in sliding manner, and are movable, by local radial deformation of the inner belt with respect to the outer belt, between an extracted position conveying cartons  4 , and a withdrawn position releasing cartons  4 .