Abstract:
A method and device for quality controlling packets of cigarettes, whereby, as a packet is fed, in use, through a quality control station, an optical detecting unit acquires data relative to given portions of the packet, which portions are coated with material optically detectable at wavelengths outside the visible range; the data detected by the optical detecting unit is compared with reference data, and the outcome of the comparison is used to determine acceptance or rejection of the packet; in this way, the condition of the packet can be determined regardless of the graphics on the packet.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims the benefit of Italian patent application number BO2004A 000221, filed Apr. 19, 2004. 
   The present invention relates to a method and device for quality controlling a packet; to a packet; and to a relative blank. 
   The present invention may be used to advantage in packing cigarettes, to which the following description refers purely by way of example. 
   BACKGROUND OF THE INVENTION 
   Packets produced on a packing machine are normally quality controlled to determine any defects, in particular, stains, scratches, or dents; and any faulty packets are subsequently rejected. 
   In U.S. Pat. No. 4,912,554, a packet is fed along a path through a quality control station where television cameras acquire an image of the packet; and the image is compared with a reference image to determine whether or not the packet is to be rejected. 
   Though efficient, the known quality control system described above has been found to fall short in some respects in terms of versatility and sensitivity. In particular, whenever changes are made to the graphics (artwork, brands, and/or colours) on the outside of the packets (e.g. so-called “brand changes”), changes must also be made to the reference image. Moreover, in areas of the packet bearing complex and/or highly coloured images, defects such as scratches or dents are especially difficult to detect. In other words, the artwork and colours on the packet act as noise during detection. 
   U.S. Pat. No. 5,877,506 discloses a device, which is designed to monitor blanks and comprises a source of infrared radiation. Such a device is designed to monitor only the contours of the blanks in order to verify the supply of the correct blanks, when there is a change in the type of packaging to be manufactured, and the correct positioning of the blanks. The device disclosed in U.S. Pat. No. 5,877,506 is not designed to control the quality of the blanks and is not designed to monitor surfaces of the blanks. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a method and device for quality controlling a packet, designed to eliminate, at least partially, the aforementioned drawbacks, and which at the same time are cheap and easy to implement. 
   According to the present invention, there is provided a method of quality controlling a packet; the method comprising a feed step to feed the packet along a feed path through a quality control station; an optical detecting step to detect at least one detected data item relative to at least one given portion of the packet; and a comparing step to compare the detected data item with at least one reference data item to determine rejection or acceptance of the packet; the method being characterized in that the given portion comprises at least a pigment, which is optically detectable at at least one given wavelength outside the visible range; the detected data item being detected by receiving electromagnetic radiation having said given wavelength from said pigment. 
   According to the present invention, there is also provided a device for quality controlling a packet; the device comprising at least one optical detector for optically detecting at least one data item relative to at least one given portion of the packet; and a comparing unit for comparing the detected data item with at least one reference data item to determine rejection or acceptance of the packet; the device being characterized in that the optical detector is designed to detect the detected data item by receiving electromagnetic radiation, which, in use, comes from at least a pigment of the given portion and has at least one given wavelength outside the visible range; the comparing unit being designed to elaborate said detected data item relating to said electromagnetic radiation coming from the pigment. 
   According to the present invention, there is also provided a packet having at least one given portion optically detectable at at least one given wavelength outside the visible range; the given portion comprising at least one first line, and at least one second line crosswise to the first line; the first and second line extending at least from a first edge to a second edge of the packet. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
       FIG. 1  shows a view in perspective, with parts removed for clarity, of a device for quality controlling packets in accordance with the present invention; 
       FIG. 2  shows a larger-scale section along line II-II of the  FIG. 1  device; 
       FIG. 3  shows a front view in perspective of a packet of cigarettes in accordance with the present invention; 
       FIG. 4  shows a spread-out view of a blank by which to form the  FIG. 3  packet; 
       FIGS. 5 to 9  show front views in perspective of alternative embodiments of packets in accordance with the present invention; 
       FIGS. 10 to 14  show spread-out views of blanks by which to form the  FIG. 5 to 9  packets respectively; 
       FIG. 15  shows a portion of the  FIG. 3  packet and the corresponding response of a detecting device; 
       FIG. 16  shows a front view in perspective of a damaged  FIG. 3  packet. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Number  1  in  FIG. 1  indicates as a whole a device for quality controlling a “rigid” packet  2  of cigarettes ( FIG. 3 ). Packet  2  comprises a cup-shaped body  3 , and a lid  4  hinged to cup-shaped body  3 . Cup-shaped body  3  comprises a front wall  5 , two lateral walls  6  (only one shown in  FIG. 3 ), a bottom wall (now shown), and a rear wall (not shown). Lid  4  comprises a front wall  5   a , two lateral walls  6   a  (only one shown in  FIG. 3 ), a top wall  7 , and a rear wall (not shown). Lateral walls  6  and  6   a  are connected to respective front walls  5  and  5   a  and to the respective rear walls (not shown) by relative longitudinal edges  8 . Front wall  5   a  and the rear wall (not shown) of lid  4  are connected to top wall  7  by relative edges  9 ; and front wall  5  is connected to the bottom wall (not shown) by an edge  10 . 
   Packet  2  is formed from a substantially flat blank  11  ( FIG. 4 ) comprising a central portion  12 , and a number of lateral panels  13  located symmetrically on opposite sides of portion  12 . Portion  12  comprises a number of panels aligned lengthwise of blank  11 ; each panel  13  is connected to portion  12  by a preformed fold line  14 ; and, once folded, fold lines  14  correspond to edges  8  of packet  2 . 
   Blank  11  has a grid  15  comprising a number of parallel longitudinal lines  16 , and a number of parallel lines  17  crosswise, in particular, perpendicular, to lines  16 . Lines  16  and  17  are invisible to the naked eye, and comprise special pigments detectable optically at a given wavelength outside the visible range, in particular at a wavelength in the ultraviolet range. 
   Device  1  ( FIG. 1 ) comprises a transfer unit  18  for feeding packet  2  along a path P through two quality control stations  19  and  20 . Device  1  also comprises two conveyors  21  and  22 , each having a suction belt  23  positioned on edge and looped about two vertical-axis pulleys  24 . Conveyor  21  receives packet  2  from an input station  25 , and feeds packet  2  through quality control station  19  to conveyor  22 ; and conveyor  22  feeds packet  2  through quality control station  20  to an output station  26 . 
   Two detecting units  27  and  28  are located at quality control stations  19  and  20  respectively, and each comprise an optical detector  29 ,  30 , and an electromagnetic radiation source  31 . Optical detectors  29  and  30  acquire data relative to grid  15  by receiving electromagnetic radiation at said given wavelength. 
   As shown more clearly in  FIG. 2 , two inclined mirrors  32  are located on opposite sides of conveyor  21  at quality control station  19 , to enable optical detector  29  to analyze lateral walls  6  and  6   a  of packet  2 . 
   Device  1  also comprises a central control unit  33  which receives the data acquired by detecting units  27  and  28 , and in turn comprises a comparing unit  34  for comparing the acquired data with reference data. On the basis of the comparison between the acquired and reference data, central control unit  33  activates a known reject device  35  (shown schematically in  FIG. 1 ) located immediately downstream from device  1  and for eliminating any faulty packets downstream from conveyor  22 . 
   In actual use, when packet  2  is located at quality control stations  19  and  20 , sources  31  emit electromagnetic radiation to bring the pigments to an excited state, decaying from which the pigments themselves emit electromagnetic radiation at said given wavelength outside the visible range. At this point, optical detectors  29  and  30  detect the shape and/or position of various areas of grid  15  and/or the intensity of the electromagnetic radiation, at the given wavelength, from the areas of grid  15 . 
   The electromagnetic radiation emitted by sources  31  and the aforementioned pigments may have different wavelengths. In the case the electromagnetic radiation emitted by sources  31  and the aforementioned pigments have indeed different wavelengths, as optical detectors  29  and  30  detects electromagnetic radiation at the aforementioned given wavelength, noise due to, for example, radiation simply reflected by packet  2  is disregarded; as a consequence, the detection of data is more precise. 
   The detected shape, position, and/or intensity are compared by comparing unit  34  with a reference shape, position, and/or intensity; and, in the event the difference between the detected and reference data exceeds given threshold values, central control unit  33  activates reject device  35 . 
   In connection with the above, it should be pointed out that, in the event packet  2  is dented, the shape and position of detected areas of grid  15  differ from the reference shape and position of packet  2  in perfect condition; and, in the event packet  2  is scratched, the intensity of the electromagnetic radiation, at the given wavelength, of the scratched area of grid  15  is below the reference intensity.  FIG. 16  shows the  FIG. 3  packet  2  with a dent along edge  10 , and the relative distorted grid  15 . 
   Optical detectors  29  and  30  preferably each comprise known area scales for detecting electromagnetic radiation, at the given wavelength, along scan lines  36 . By way of example,  FIG. 15  shows an area of grid  15 , and the corresponding area scale response along scan line  36 . The y axis shows the position along the scan line, and the x axis the intensity of the relative pixels. In this case, the comparing unit compares the positions, heights, and/or shapes of the peaks in  FIG. 15  with reference positions, heights, and/or shapes. 
   Device  1  as described above allows changes to be made to the graphics (artwork, brands, and/or colours) on the outside of packet  2  (e.g. so-called “brand changes”) without changing the reference data, and also provides for accurately determining the condition of packet  2 , even in areas of packet  2  bearing complex and/or highly coloured images. 
   In this connection, it should be pointed out that, since optical detectors  29  and  30  only detect electromagnetic radiation at said given wavelength outside the visible range, whatever is picked up by optical detectors  29  and  30  is unaffected by the graphics on the outside of packet  2 . 
     FIGS. 5 to 14  show alternative embodiments of packet  2  and relative blank  11 . As can be seen, packets  2  in  FIGS. 5 to 9  are substantially similar to packet  2  described above, except that grid  15  is replaced by one or more given portions  37  of various forms and comprising said pigments. 
   Grid  15  is preferably stamped on blank  11  off the packing machine, i.e. at the packing material manufacturer&#39;s plant or paper mill. Alternatively, the grid may be stamped on the blank by means of a stamping device upstream from the packing machine. 
   The  FIG. 5  packet  2 , formed from the  FIG. 10  blank, comprises one portion  37  on lateral wall  6   a  of lid  4 . In this case, in the event the lateral panel  13  partly defining wall  6   a  is not glued properly and is therefore partly raised, optical detector  29  can detect portion  37  directly, and not only by means of one of mirrors  32 . In  FIGS. 5 and 10 , portion  37  is hatched. 
   In the  FIG. 6  packet  2 , formed from the  FIG. 11  blank  11 , portion  37  extends along the edges of packet  2 . As shown in  FIG. 11 , portion  37  extends at least partly along the edge of blank  11 . In  FIGS. 6 and 11 , portion  37  is hatched. 
   In the  FIG. 8  packet  2 , formed from the  FIG. 13  blank  11 , portion  37  comprises two substantially perpendicular lines on front wall  5 , one extending from one longitudinal edge  8  to the other longitudinal edge  8 , and the other extending from edge  9  to edge  10 . In  FIGS. 8 and 13 , portion  37  is shown by bold lines. 
   In the  FIG. 7  packet  2 , formed from the  FIG. 12  blank  11 , portion  37  comprises two substantially perpendicular lines, a first extending on front wall  5 , lateral walls  6 , and the rear wall (not shown in  FIG. 7 ) of cup-shaped body  3 , and a second extending on front walls  5  and  5   a , on the bottom and rear walls (not shown in  FIG. 7 ) of cup-shaped body  3 , and on top wall  7  and the rear wall (not shown in  FIG. 7 ) of lid  4 . In  FIGS. 7 and 12 , portion  37  is shown by bold lines. 
   The  FIG. 9  packet  2 , formed from the  FIG. 14  blank  11 , has a portion  37  comprising a number of lines, which extend along the edges of packet  2 , and which, from the corners, intersect on each wall  5 ,  5   a ,  6 ,  6   a ,  7 , each of the rear walls (not shown), and the bottom wall (not shown). In  FIGS. 9 and 14 , portion  37  is shown by bold lines. 
   Though the above description and accompanying drawings relate to a conventional hinged-lid packet of cigarettes, the teachings of the present invention obviously also apply to packets of cigarettes of any type, such as a hinged-lid packet with rounded or bevelled edges, or a “soft” packet of cigarettes. The teachings of the present invention obviously also apply to cartons of packets of cigarettes, and to packets of other than cigarettes, such as packets of food products, confectionary, or toiletries.