Abstract:
The invention relates to a method for checking that batches of cigarettes are complete and that the cigarettes are sufficiently filled. In spite of careful manufacturing, when cigarettes are produced and batches of cigarettes are filled in cigarette packs ( 11 ) using high-performance machines, it is possible that some of the packs of cigarettes manufactured have cigarettes missing or contain cigarettes which are not sufficiently filled with tobacco. The invention provides an improved, non-contact method of checking the batches of cigarettes or the individual cigarettes. According to this method, the intensity signal of a CCD camera or a CCD-line-scanning chip in subareas of the front ends ( 24 ) of the cigarettes and/or the spaces between them is measured and analysed in the front end area of the batch of cigarettes. The inventive method therefore provides a means of checking that batches of cigarettes are complete and that the cigarettes are sufficiently filled in high-performance machines such as pocket conveyors or revolving folders.

Description:
DESCRIPTION 
     The invention relates to a method for checking ordered cigarette groups corresponding to the content of a cigarette pack with an electro-optical checking element, preferably a CCD linear array chip or a CCD camera, connected to a signal data processing arrangement, for the measurement of the intensity of light reflected by filter-side ends of the cigarettes. Furthermore, the invention relates to a method for checking ordered cigarette groups corresponding to the content of a cigarette pack with an electro-optical checking element, preferably a CCD camera, connected to a signal data processing arrangement, for the measurement of the intensity of reflected light, a measurement zone preferably formed from pixels of the checking element being assigned to at least one partial area of the ends of the cigarettes. 
     High-performance machines are required to produce cigarettes and fill cigarette groups in cigarette packs. Despite careful manufacturing, however, it is often the case that the cigarette packs that have been produced and delivered to the customer have cigarettes missing or contain cigarettes inadequately filled with tobacco. When selecting checking methods for separating out such defective cigarette groups, it has to be taken into account that the checking must take place in a fast, continuous or batchwise conveying process. 
     In a checking method used previously, an ordered cigarette group corresponding to the content of a cigarette pack is moved past a checking device in which the intensities of reflected light which are measured by a CCD camera are statistically evaluated. 
     The invention is based on the object of proposing an improved, contactless checking method for monitoring that cigarette groups are complete and/or that the cigarettes are filled with tobacco. 
     In order to achieve this object, the method according to the invention is characterized in that a measurement zone formed by the checking element, preferably by the pixels of the CCD linear array chip or the CCD camera, is assigned to the ends of the cigarettes and the cigarette interspaces formed between the latter, at least partial areas of the measurement zone, in particular pixels of the CCD camera or of the CCD linear array chip, are arranged in curved or rectilinear, in particular horizontal or vertical, evaluation bars, and the measurement signal measured along the evaluation bars is evaluated in the signal data processing arrangement in order to check that the cigarette group is complete. 
     The measurement element for checking the cigarette groups thus operates contactlessly on the basis of a CCD linear array chip or a CCD camera, so that the cigarette group can be checked even with a fast conveying cycle. In this case, the measurement element can be arranged at any desired point in the conveying process as long as the ends of the cigarette groups are freely accessible in this. By way of example, the checking can be carried out during the conveying process in a pocket conveyor. A further possibility is for the cigarette groups to be checked in a folding turret. 
     According to the invention, in a further refinement with regard to the evaluation of the intensity profile yielded by the CCD camera or the CCD linear array chip, the method is characterized in that the number of cigarettes in the region of the evaluation bar or bars is determined from a count of the crossings of the intensity profile through a threshold value with the threshold value subsequently being exceeded and/or undershot. This evaluation method is based on the fact that the reflected light in the region of the light filter areas of the cigarettes is greater than the intensity measured in the region of the dark cigarette interspaces formed by adjacent cigarettes. A rise in the measured intensity profile can thus be evaluated as a transition from a cigarette interspace to a filter-side end of a cigarette. If a cigarette is missing in a row of cigarettes, the number of times that the high intensity is reached in the region of the filter areas is thus one fewer than in the case of a complete row of cigarettes. This is detected from the count of the crossings of the intensity profile through a threshold value. 
     If a cigarette is missing within a cigarette group with a plurality of rows of cigarettes, adjacent cigarettes are displaced. The consequence of this is that the distance between the first and last cigarettes in a row of cigarettes is reduced on account of a cigarette being missing. Therefore, a further method according to the invention is characterized in that the completeness of the cigarette group is determined from the comparison of the distance between the first and last crossings of the intensity profile through a threshold value with a desired value. 
     The number of high measured intensity values increases with the number of filter-side end areas of the cigarettes in the region of the evaluation bar of the CCD linear array chip or CCD camera. Accordingly, in a further method according to the invention, the area, determined in particular by summation of the intensity values measured along the evaluation bar, underneath the curve of the measured intensity signal can be compared with a desired value determined for the complete cigarette group. 
     In order to achieve the object, a further method according to the invention is characterized in that a measurement signal measured in the pixels assigned to the ends of the cigarettes and also the cigarette interspaces is evaluated in accordance with the horizontal and vertical positions of the pixels as a two-dimensional measurement zone. 
     In a three-dimensional representation of the measured intensity against the horizontal and vertical positions of the pixels in the two-dimensional measurement zone, the intensity profile can thus be represented as a curved area having high plateaus in the region of light cigarette areas, for example in the region of the light end areas of the cigarettes, and valleys for the regions with low measurement intensities, for example in the region of the cigarette interspaces. 
     In a method according to the invention, this relief-like changeover of mountains with high plateaus and valleys is evaluated in such a way that, in the case where the measurement zone is arranged on the tobacco side, the presence of a large number of small adjacent intensity values is used as an indicator of recesses in the filling of the cigarettes with tobacco. In this checking method, therefore, valleys, that is to say a real regions with small adjacent intensity values, are deliberately sought. In the region of a valley, an a real shadow region is present at the tobacco-side end of the cigarette. This can be assessed as an indicator of recesses in the filling of the cigarettes, so-called voids. 
     If a cigarette is missing from a cigarette group and the cigarettes are checked in the region of the filter-side end areas of the cigarettes, the fact that a cigarette is missing from the cigarette group has the consequence that a “valley” with low measurement intensities is present in the region at which a plateau with high intensity should be present for a complete cigarette group. Therefore, in the region of the desired positions of the end filter areas, a large number of low measurement intensities are measured instead of a large number of adjacent high measurement intensities. In the case of the determination of the frequency distribution of the measured values with measurement intensities within predefined intensity classes, the occurrence of a large frequency in conjunction with large measurement intensities indicates the presence of a light filter area, while the presence of large frequencies in conjunction with small measurement intensities can be evaluated as an indicator of a dark cigarette interspace. Further methods relate to preferred refinements of the invention. 
    
    
     Further details of the methods are explained in more detail below using the exemplary embodiments illustrated in the drawings, in which: 
     FIG. 1 shows a conveying device for soft-carton packs in side view, 
     FIG. 2 shows a checking device for checking cigarette groups in plan view, 
     FIG. 3 shows a defective cigarette group in the pocket of a pocket conveyor, 
     FIG. 4 shows horizontal and vertical evaluation bars for checking a cigarette group, 
     FIG. 5 shows an example of a measured intensity signal along a horizontal evaluation bar, 
     FIG. 6 shows an example of a measured intensity signal along a vertical evaluation bar, 
     FIG. 7 shows measurement regions of the checking method in the filter region and in the region of t he cigarette interspaces, 
     FIG. 8 shows the frequency distribution of measured intensities in the filter region, 
     FIG. 9 shows the frequency distribution of measured intensities in the region of the cigarette interspaces, 
     FIG. 10 shows the measurement result from the CCD camera, measured at the tobacco-side en d in the region of a correctly filled cigarette group, 
     FIG. 11 shows the measurement result from the CCD camera, measured at the tobacco-side end in the region of an incorrectly filled cigarette group, 
     FIG. 12 shows a three-dimensional representation of the intensity profile, 
     FIG. 13 shows a block diagram of the measurement control and signal data processing arrangement for monitoring that the cigarette group is complete and filled. 
    
    
     The details illustrated in the drawings relate to a preferred application example, namely to the manufacturing of cigarette packs of the soft-carton pack type. FIG. 1 shows the basic design of a packaging machine  10  for manufacturing such cigarette packs  11 . The cigarettes are transferred to the packaging machine  10  in the region of a cigarette magazine  12 . This is a customary element in packaging machines  10  for cigarettes for storing cigarettes and for delivering cigarette groups  13  in accordance with the content of a cigarette pack  11 . For this purpose, the cigarette magazine  12  is provided with magazine shafts  14  in the lower region, which are combined as shaft groups. A cigarette group  13  is pushed by slides out of each shaft group and into pockets  15  of a pocket chain  16 , to be precise in the region of a lower conveying strand  17 . 
     The pocket chain  16  transports the cigarette groups  13  to a folding turret  18 , to which they are transferred by being pushed out of the pockets  15  of the pocket chain  16 . Details of the structure of the cigarette magazine  12 , the pocket chain  16  and the folding turret  18  can be found in EP 226 872. 
     At the positions in the conveying stream which are marked by the arrows A and B, namely in the region of the lower conveying strand  17  and in the folding turret  18 , the cigarette groups  13  are checked to see whether they are complete or whether the cigarettes are completely filled, by means of the checking method according to the invention. An ejector  20  is arranged downstream of the checking device  19  in the conveying direction, which ejector is actuated in the event of an error signal from the checking device  19  for the purpose of separating out defective cigarette groups  13 . 
     The checking device has a checking element  21 , preferably a CCD linear array chip or a CCD camera. An optical arrangement  22  is arranged upstream of the checking element  21 . Other parts of the checking device are, by way of example, two light sources  23 , which are preferably inclined at an angle of 5 to 15° with respect to the recording direction of the checking element  21 . Checking element  21  and assigned light sources  23  are oriented in such a way that the light from the light sources  23  which is reflected from an end  24  of the cigarette pack  11  is detected by the checking element  21 . In this case, the light source  23 , preferably a high-intensity light source or a laser, can be activated stroboscopically in time with the machine cycle. In the exemplary embodiment illustrated in FIG. 2, a checking device  19  is arranged at the filter-side end  24  of the cigarette packs  11 . The cigarette group is monitored for completeness here, for example. A further checking device is arranged at the tobacco-side end  24  of a cigarette group  13 . This further checking device can be used for example to monitor that individual cigarettes  25  are completely filled; however, it is also possible to effect simultaneous monitoring to see whether the cigarette group  13  is complete and the cigarettes  25  are filled with tobacco. 
     FIG. 3 shows the filter-side end  24  of a cigarette group  13  and also a pocket  15  of the pocket chain  16 , the said pocket being assigned to the cigarette group  13 . At the pocket  16 , provision is made of a vertical marking  26  and a horizontal marking  27  for the orientation of the image of the checking element  21 . If the pocket  15  is displaced vertically, the horizontal marking  27  is displaced vertically; if there is a short time delay during the recording of an intensity profile  28  by the checking element  21 , that is to say the CCD camera or the CCD linear array chip, the vertical marking  26  is displaced laterally from its desired position in the recorded image. The image recorded by the CCD camera is oriented using the markings in the coordinate system of the evaluation unit. 
     By way of example, a complete cigarette group  13  has seven cigarettes  25  in each outer horizontal row  29  of cigarettes and the inner horizontal row  30  of cigarettes comprises six cigarettes. Consequently, the cigarette group  13  illustrated is a defective group. On account of a missing cigarette in the inner row  30  of cigarettes, two cigarettes  31  and  32  from the outer rows  29  of cigarettes have been displaced into the interior of the pocket  15  in a manner deviating from their desired positions. Such defective groups are separated out using the following measurement regions: 
     the dash-dotted circles  33  mark the desired positions of the cigarettes in the cigarette group, 
     the circular areas with a solid border  34  are partial areas of the cigarette end, whose significance for the evaluation method is explained below, 
     further evaluation areas are the shadow areas  35  marked by black circular areas in the region of the cigarette interspaces  36 , 
     in FIG. 4, horizontal lines mark horizontal evaluation bars  37 , which preferably run in such a way that an evaluation bar passes through not only the region of the desired position of each cigarette  33  in a row  29  or  30  of cigarettes but also a shadow region  35  in the region of two adjacent cigarettes in a row  29  or  30  of cigarettes, 
     vertical evaluation bars  38  are preferably arranged in such a way that the cigarette interspaces  36  between cigarettes of adjacent rows of cigarettes are traversed in the vertical direction. 
     The circular areas  34  and shadow regions  35  can, of course, also have a contour which differs from the circular form illustrated. To determine the completeness of a row  29 ,  30  of cigarettes, the light intensity reflected along a horizontal evaluation bar  37  is measured by a checking element  21  in an evaluation method according to the invention. To that end, the evaluation bar  37  is imaged by a plurality of pixels of the CCD linear array chip or CCD camera. In this case, each pixel detects the light intensity of a partial section of the evaluation bar  37 . In FIG. 5, the horizontal evaluation bar  37  is divided into 230 partial sections of the same size by 230 pixels. The measurement signal  39  illustrated represents the measured intensity for the pixels  0  to  229 . The light intensity is usually specified in the candela unit. The CCD camera converts the intensity at the measurement location into a proportional measurement signal, for example into a voltage. For this reason, the measured values for the intensities are specified without units below. The absolute values of the measured values are denoted by square brackets in the text below. 
     The intensity of the reflected light is large in the region of the pixels assigned to the (light) ends  24  or filters of the cigarettes; in this respect, see the high-intensity plateaus  40  in FIG.  5 . The intensity dips in the region of the pixels assigned to the shadow regions  35  between the cigarettes  25 . The measured error signal  41  for the case where a cigarette is missing is represented here by a dash-dotted line. 
     By way of example, the method for evaluating the measurement signal  39  can count the crossings  42  of the measurement signal through a threshold value  43 . In the example illustrated, the measurement signal  39  passes through the threshold value  43  seven times in the positive and negative directions. There are thus seven cigarettes in the row  29 ,  30  of cigarettes. 
     A further method determines the area under the measurement signal  39  illustrated in FIG.  5 . The said area can be determined by summation of the intensities measured by the pixels  0  to  229 . The deviation of a sum determined in this way from a desired value can be assessed as an indicator of the fact that a cigarette  25  is missing in the row  29 ,  30  of cigarettes, since, in the region of the error signal  41  marked by the dash-dotted line, on account of the missing cigarette  25 , the error area  44  under the curve is very much smaller than the comparison area  45 , in other words only small values enter into the summation. 
     In a further evaluation method, the intensity measured by pixels assigned to the vertical evaluation bars  38  is evaluated; in this respect see FIG.  6 . The vertical evaluation bars  38  pass through the cigarette end areas preferably in the immediate vicinity of the end area midpoint  46 . The two high-intensity plateaus  47  in the measurement signal  39  illustrated in FIG. 6 in this case identify measurements in the region of an end  24 . The edge region  48  of a cigarette  25  in the inner row  30  of cigarettes is passed through between the two plateaus  47 , so that here the intensity rises over a smaller width and forms a local maximum  49 . In accordance with the method outlined above, the exceeding or undershooting of a threshold value  43  can be used for evaluation purposes in this case, too. In a simplification of this method, however, only the first crossing  50  of the measurement signal  39  through the threshold value  43  and the last crossing  51  of the measurement signal  39  through the threshold value  43  are evaluated. The distances D 1  and D 2  can be determined from the pixel assigned to this first crossing  50  and last crossing  51 , respectively. As an alternative, the first crossing can, of course, also be determined from both sides or from above and from below (with regard to the measurement direction, also see the arrows in FIG.  4 ). 
     The fact that a cigarette  25  is missing in the cigarette group  13  has the consequence that the distance between adjacent cigarettes  25  and the side wall  52  of the pocket  15  is increased; in this case, see cigarettes  31  and  32  in FIG.  3 . This results in an increase in the distances D 1  and D 2 . An error signal can be determined from the comparison of the sum D 1 +D 2  with a desired value. By analogy with this, it is also possible, of course, to use the distance D between the first crossing  50  and the last crossing  51  for the evaluation. 
     Problems may be posed by the application of the checking method described to the case of checking the cigarette group  13  in the region of the folding turret  18 . In the folding turret, the cigarette groups  13  are not surrounded by dark pockets  15 , but rather by light packaging material. Consequently, it can happen that the measurement signal  39  has high intensities outside the cigarette group  13  and, for this reason, a first and a last crossing  50 ,  51  are not present. In this case, it is possible to use a further method for determining the completeness of the cigarette group  13 , which method is based on the intensities measured in the partial area, namely circular area  34  of the end  24  and the shadow regions  35 . In this case, a plurality of pixels are arranged in the circular areas  24  of the filter-side end area of a cigarette. The light filter-side ends  24  reflect light with a high intensity, for example intensities between [ 59 ] and [ 63 ], see FIG.  8 . For the evaluation of the intensities measured in pixels assigned to the partial areas of the end  24 , a plurality of classes  54  of intensity are formed, for example classes  54  having intensity values in the region of [ 59 ]-[ 60 ], [ 60 ]-[ 61 ] and [ 61 ]-[ 62 ]. In the measurement result illustrated in FIG. 8, the frequency N of the pixels is represented for each intensity class for a measurement in the region of the filter-side end  24 , the frequency  72  being plotted against the intensity class  71 . An intensity &gt;[ 60 ] was thus measured for more than  238  pixels. In this case, the number of pixels with intensities below a threshold value is approximately zero if the filter-side end  24  of the cigarette  25  is situated in the desired position (in practice, the intensity below a threshold value is approximately zero on account of measurement inaccuracies). 
     If a cigarette  25  is missing from the cigarette group  13 , the remaining cigarettes  25  of the cigarette group  13  are displaced. The consequence of this is that shadow regions  35  are displaced into the light filter-side desired positions of the cigarettes  33 . Therefore, if measured values with intensities below the threshold value  55  are present, this can be evaluated as an indicator of an erroneous position of one or more cigarettes  25 . In the case of digitized intensity values, the classes can also be formed from the digitization levels, so that pixels of the same intensity are then summed. 
     For measurements in the shadow region  35  in the cigarette interspace  36  between adjacent cigarettes  25 , the intensity of the reflected light is very small; in this respect, see FIG.  9 . The number of pixels is smaller in this case, since the assigned measurement areas for the shadow regions  35  are smaller. For a partial area of the measurement zone which lies in the desired region of the shadow regions  35 , the number of pixels with intensities greater than a predefined threshold value  56  is zero. The displacement of the remaining cigarettes  25  from their desired position  33  due to a cigarette  25  being missing from the cigarette group  13  has the consequence that light filter areas are arranged in the desired positions  33  of the shadow regions  35 . Therefore, if measured values with intensities above a threshold value  56  are present for measurements in the shadow region  35 , this can be evaluated as an indicator of the erroneous position of one or more cigarettes  25 . 
     In a further measurement method, a measurement area  57 , in the region of the tobacco-side end  24  of the cigarette group  13 , is divided into a plurality of pixel areas  58 , to each of which a pixel of the CCD camera is assigned. FIG. 10 shows an enlarged detail of the measurement area  57 , in which each square describes the pixel area  58  detected by a pixel and the numerical value assigned to this square describes the brightness measured in the pixel area  58 . In this case, dark pixel areas  58  identify regions with low intensities, that is to say dark end-area regions, and bright pixel areas  60  identify light measurement areas. 
     In this case, the circular contours  61  formed by pixels with high measurement intensities correspond to the outer contour of the cigarettes  25 , since the light casing around the tobacco reflects light with high intensity. Inside the casing, the intensity fluctuates very greatly at average values. This can be attributed to the fact that the end  24  formed by the tobacco is uneven. In this case, FIG. 10 illustrates the measurement result of correctly formed cigarettes  25 . In the region of the end  24  of the cigarette  25  formed by the tobacco, the intensity fluctuates very greatly, but there are no large areas with low intensity which are formed by a plurality of adjacent pixel areas  58 . If the cigarettes are deficiently filled with tobacco, recesses may be formed from the end area of the cigarettes. These regions are identified by regions with a low measurement intensity which are formed from a plurality of pixel areas  58 ; in this respect, cf. FIG.  11 . Counting the number of adjacent pixel areas  58  with intensities below a predefined threshold value can thus be used as an indicator of inadequately filled cigarettes  25 . 
     FIG. 12 shows a detail from the result of the intensity measurement by means of the checking element, for example a CCD camera, with arrangement on the filter side. In this case, the intensity  75  is plotted against the x-axis  73  and the y-axis  74 , that is to say as a function of the horizontal and vertical measurement positions. In this case, the plateaus  62  with high intensities can be discerned in the region of the light filter-side ends  24 . Each plateau  62  is formed by the measured intensities of many pixels, in this case approximately  500 . In the dark shadow regions  35  of adjacent cigarettes  25 , valleys  63  are formed in the three-dimensional representation. In the case of a correctly formed cigarette group  13 , 7+6+7=20 such plateaus  62  separated by valleys  63  are accordingly present; if a cigarette  25  is missing, one plateau  62  is replaced by an additional valley  63 . The volume under a measurement area  64  produced in this way is dependent on the number of plateaus  62 . Accordingly, the deviation of the volume that has been determined from a desired value can be evaluated as an indicator of missing cigarettes  25 . The determination of the volume is in this case proportional to the sum of the individual intensities measured in the measurement area  64 , so that the volume or an amount proportional thereto can be determined in a simple manner. It goes without saying that an evaluation method of this type can also be carried out at the tobacco-side ends  24  of the cigarette group  13 , so that the checking of the completeness of the cigarette group  13  and of the filling of the cigarettes  25  can be effected by one checking element  21  in this case. 
     In order to increase the reliability of the checking method, it is also possible, of course, for a plurality of the checking methods that have been explained to be used simultaneously. 
     The measurement methods that have been explained have the following block diagram  65  for the signal data processing and the machine control in common, see FIG.  13 : 
     The checking operation is started by a trigger signal  66 , which is generated for example by a light barrier when a new pocket  15  with cigarette group  13  enters the checking region. This trigger signal  66  is fed to the image processing arrangement  67 , which activates a light source  23 , for example a laser, stroboscopically. At the same time as the cigarette group  13  is exposed to the flashing, an image is recorded by means of the checking element  21 , for example a CCD linear array chip or a CCD camera, and fed to the image processing arrangement  67 . This image is fed via a suitable I/O interface  68  to the machine control  69 . In addition to monitoring that the cigarette group  13  is complete and that the cigarettes  25  are filled with tobacco, the signal data processing arrangement  70  must also monitor whether the checking elements  21  are operationally available, the image from the checking element  21  is recorded at the correct instant and/or the signal quality is sufficient. By way of example, in the event of deficient light conditions on account of a defective light source  23 , an error signal must be generated, so that the machine can be stopped and the light source  23  exchanged. The machine control  69  is furthermore connected to an ejector  71 , so that if an incomplete cigarette group  13  or incomplete filling of the cigarettes  25  is identified, the ejector  71  can be actuated for the removal of the defective cigarette group  13 . It goes without saying that a plurality of separate checking devices  19  can also be activated and evaluated simultaneously or successively. 
     LIST OF REFERENCE SYMBOLS 
       10  Packaging machine 
       11  Cigarette pack 
       12  Cigarette magazine 
       13  Cigarette group 
       14  Magazine shaft 
       15  Pocket 
       16  Pocket chain 
       17  Lower conveying strand 
       18  Folding turret 
       19  Checking device 
       20  Jector 
       21  Checking element 
       22  Optical arrangement 
       23  Light source 
       24  End 
       25  Cigarette 
       26  Vertical marking 
       27  Horizontal marking 
       28  Intensity profile 
       29  Outer row of cigarettes 
       30  Inner row of cigarettes 
       31  Cigarette 
       32  Cigarette 
       33  Desired position of the cigarette 
       34  Circular area 
       35  Shadow region 
       36  Cigarette interspace 
       37  Horizontal evaluation bar 
       38  Vertical evaluation bar 
       39  Measurement signal 
       40  Plateau 
       41  Error signal 
       42  Crossing 
       43  Threshold value 
       44  Error area 
       45  Comparison area 
       46  End area midpoint 
       47  Plateau 
       48  Edge region 
       49  Local maximum 
       50  First crossing 
       51  Last crossing 
       52  Side wall 
       53  Filter 
       54  Class 
       55  Threshold value 
       56  Threshold value 
       57  Measurement area 
       58  Pixel area 
       59  Dark pixel area 
       60  Bright pixel area 
       61  Circular contour 
       62  Plateau 
       63  Valley 
       64  Measurement curve 
       65  Block diagram 
       66  Trigger signal 
       67  Image processing arrangement 
       68  I/O interface 
       69  Machine control 
       70  Signal data processing arrangement 
       71  Intensity class 
       72  Frequency 
       73  x-axis 
       74  y-axis 
       75  Intensity