Patent Document

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method for inspecting cigarette heads, where light radiates in at least two strip-like portions, which are incident from different directions, onto the end area of a cigarette head and light reflected from the end area is received by a detector and evaluated. Furthermore, the invention relates to an apparatus for inspecting cigarette heads having at least two light sources for illuminating a respective strip-like portion of an end area of a cigarette head from different directions, and having a detector for receiving light reflected from the end area. 
     2. Description of Prior Art 
     Inspection methods and inspection apparatuses for the contactless inspection of cigarette heads are known, in which one or more straight lines is or are radiated onto the cigarette head on the tobacco side. If the cigarette is not properly filled with tobacco, the line—when it is observed from a different viewing angle—no longer appears as a straight line but rather as a wavy line or as an interrupted wavy line. This image is acquired by a sensor. Finally, the pixels lying inside and outside a narrow region around an imaginary, theoretical straight line are counted and put into a ratio with respect to one another. If this ratio exceeds a limit value, this is suppose to indicate that a cigarette is not properly filled. 
     This type of inspection has the disadvantage that it is inaccurate and does not allow exact statements to be made about the state of a cigarette. 
     Therefore, the invention is based on the problem of improving the inspection of cigarettes and providing more accurate statements about the state of a cigarette. 
     SUMMARY OF THE INVENTION 
     In order to solve this problem, the method according to the invention is defined by the fact that, in the course of evaluation, a distance between two lines which are produced from a signal generated by the detector and correspond to the strip-shaped portions is determined in order to establish the position of that region of the cigarette head which is irradiated by the portions. Furthermore, the problem is solved by means of an apparatus according to the invention, which has an evaluation device for evaluating a signal generated by the detector, which evaluation device is designed to determine a distance between two lines which are produced from the signal and correspond to the strip-shaped portions, in order to establish the position of that region of the cigarette head which is irradiated by the portions. 
     The invention makes use of the insight that two light bands which run toward one another and impinge as strips of light on an object to be measured, namely a cigarette head, provide information about the distance between the object to be measured and the measuring arrangement or another fixed point, or generally about the position of the object to be measured. In this case, the distance between the two strips of light which impinge on the object to be measured provides the desired information about the position of the object to be measured. 
     This type of contactless inspection of cigarette heads is suitable in particular for recessed filter cigarettes or Papyrossi cigarettes, in which case, with these cigarettes, the strips of light also at least partially impinge on the end of the cigarette casing or the tip sleeve and the light reflected from these regions as well is received by the detector and evaluated. As a result, a point-like light spot is obtained when the strip of light impinges upon or intercepts the casing or tip sleeve. These point-like light spots provide an orientation point for the end of the cigarette or of the tip. The strips of light which impinge on the tobacco or filter are set back relative to the end edge of the tip in the case of these cigarettes (with a hollow tip). The depth of the tip sleeve can therefore be established from a distance between the images of these point-like light spots or strips of light on the detector. 
     The result of the inspection can be used to generate a error signal if a cigarette does not comply with predetermined limit values. Such an error signal leads to the ejection of a cigarette in the cigarette production or packaging process. Preferably, a formation comprising a plurality of layers of cigarettes is simultaneously inspected and, if appropriate, the entire formation is ejected if a defective cigarette occurs. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Further preferred embodiments of the invention emerge from the subclaims and from the exemplary embodiments illustrated in the drawing. In the drawing: 
     FIG. 1 shows an inspection apparatus according to the invention for inspecting heads of a cigarette formation with a light source arranged directly upstream of a lens-diaphragm system; 
     FIG. 2 shows a section along the Line II—II in accordance with FIG. 1, which shows the end areas of cigarette heads of a cigarette formation which are illuminated by strips of light; 
     FIG. 3 shows a section along the Line III—III in accordance with FIG. 2, which shows the geometrical structure of the incident light beams in order to elucidate the distance conditions of the strips of light; 
     FIG. 4 a  shows the tobacco-side end of a correctly formed cigarette in longitudinal section; 
     FIG. 4 b  shows the end area of the cigarette head from FIG. 4 a  illuminated by two strips of light, as it is imaged on a detector; 
     FIG. 4 c  shows the centroid lines of the images in accordance with FIG. 4 b  on the detector, said centroid lines having been calculated by an evaluation device; 
     FIG. 5 a  shows the tobacco-side end of an excessively short cigarette in longitudinal section; 
     FIG. 5 b  shows the end area of the cigarette head from FIG. 5 a  illuminated by two strips of light, as it is imaged on a detector; 
     FIG. 5 c  shows the centroid lines of the images in accordance with FIG. 5 b  on the detector, said centroid lines having been calculated by an evaluation device; 
     FIG. 6 a  shows the tobacco-side end of a cigarette in longitudinal section with a vacancy in the tobacco in the form of a hole; 
     FIG. 6 b  shows the end area of the cigarette head from FIG. 6 a  illuminated by two strips of light, as it is imaged on a detector; 
     FIG. 6 c  shows the centroid lines of the images in accordance with FIG. 6 b  on the detector, said centroid lines having been calculated by an evaluation device; 
     FIG. 7 a  shows the cigarette head of a correctly formed recessed filter cigarette in longitudinal section; 
     FIG. 7 b  shows the end area of the cigarette head from FIG. 7 a  illuminated by two strips of light, as it is imaged on a detector; 
     FIG. 7 c  shows the centroid lines of the images in accordance with FIG. 7 b  on the detector, said centroid lines having been calculated by an evaluation device; 
     FIG. 8 a  shows a cigarette head of a recessed filter cigarette in longitudinal section with an obliquely clipped filter; 
     FIG. 8 b  shows the end area of the cigarette head from FIG. 8 a  illuminated by two strips of light, as it is imaged on a detector; 
     FIG. 8 c  shows the centroid lines of the images in accordance with FIG. 8 b  on the detector, said centroid lines having been calculated by an evaluation device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows an inspection apparatus  10  for inspecting a cigarette formation  11  comprising cigarettes  12  arranged in three layers. The inspection apparatus  10  has two light sources  13  and  14 , which each preferably comprise a laser but may also comprise another bright light source, for example an arrangement of bright light-emitting diodes. The emitted light is therefore monochromatic and coherent or monochromatic and non-coherent or non-monochromatic and non-coherent. The light sources  13 ,  14  are either turned on permanently, or, alternatively, may be operated in a pulsed fashion, so that they generate short flashes of light. 
     The light beams  15 ,  16  issuing from the light sources  13 ,  14  each pass to an optical arrangement or to a lens-diaphragm system  17 ,  18  or to a hologram, which convert the light beams  15 ,  16  in each case in three light bands  19 ,  20 ,  21  and  22 ,  23 ,  24 . These light bands  19  to  24  fall onto cigarette heads  25  of the cigarettes  12 , where the light bands  19  to  24  have the configuration of strip-like portions  26  to  31 , as illustrated in FIG.  2 . FIG. 2 shows the end areas of the cigarette heads  25  from FIG.  1 . The cigarette formation  11  comprises three layers, the outer two layers comprising seven cigarettes and the middle layer comprising six cigarettes. For each layer, two strip-like portions  26  and  27 , and  28  and  29 , and  30  and  31  impinge on the end areas. The respective upper strip-like portions  26 ,  28 ,  30  originate from the light source  13  illustrated at the top of FIG.  1 . The lower strip-like portions  27 ,  29 ,  31  correspondingly originate from the lower light source  14 . 
     Each strip-like portion  26  to  31  covers a wide region of the end area of the respective cigarette heads  25 , to be precise in each case somewhat less than half of the end area of a cigarette head. Therefore, essentially total coverage of the cigarette end area is obtained by two strip-like portions. This has the advantage that it is thereby possible to evaluate virtually the entire end area. 
     FIG. 1 shows a detector  32 , which receives light  33  reflected from the end areas. The detector  32  has an optical arrangement  34 , which serves for focusing the reflected light  33  onto a sensor. This sensor contained in the detector  32  as a CCD chip having a multiplicity of two-dimensionally arranged CCD elements. As a result, it is possible to generate the images of the strip-shaped portions  26  to  31  on the end areas of the cigarette heads on the CCD chip. The individual CCD elements each output a signal which flows to an evaluation device. 
     The inspection apparatus  10  that is described is preferably situated on the cigarette turret of a cigarette packaging machine. However, it may also be arranged in a similar form on the cigarette magazine and there perform presorting or ejection of individual cigarettes by means of an ejector arranged on the magazine, as is described in the published German Patent Application DE 36 20 735 A1. In the case of an inspection apparatus arranged on the cigarette turret, the identification of a defective cigarette leads to the entire cigarette formation  11  being ejected. For this purpose, the inspection apparatus generates an error signal which causes the ejector to perform ejection. 
     FIG. 3 shows a section along the Line III—III from FIG. 2, that is to say a longitudinal section through a cigarette head  25 . This cigarette head  25  has a filter piece  35  set back relative to the end of the tip sleeve  36 . The incident light bands  20 ,  23  irradiate the strip-shaped portions  28 ,  30  at the end of the filter piece  35 . In addition, the light bands  20 ,  23  also irradiate the end of the tip sleeve  36  at end portions  37 ,  38 . These portions  28 ,  29 ,  37 ,  38  illustrate the illuminated portions in the case of a recessed filter cigarette. A similar picture would be produced for a Papyrossi cigarette, the filter piece  35  in that case being replaced by tobacco, however. 
     The broken lines illustrated in FIG. 3 show the conditions for an excessively long cigarette  12 . In the case of such a defective cigarette, the end area  39  of the filter piece  35  would end offset to the right, as would the end edge of the tip sleeve  40 . 
     In the case of a properly formed cigarette, the portions  28  and  29  are at a specific distance from one another, as are the portions  37 ,  38  or the distances between the portions  28  and  37  or  38  and also  29  and  38  or  37 . Defects of the cigarette heads can be inferred from these distances. Specifically, as shown in FIG. 3, these portions  28 ,  29 ,  37 ,  38  are displaced away from the formation if a cigarette is too long. Thus, the portion  28  is displaced to the broken line  28 ′ shown, and  29  is displaced to the broken line  29 ′ shown, and the end portions  37  and  38  are also displaced to broken lines  37 ′ and  38 ′, respectively. 
     FIG. 4 a  shows a longitudinal section through a cigarette head  41  of a tobaccoless cigarette with an end area  42 . FIG. 4 b  shows the image produced on the detector  32  when the end area  42  is illuminated by two light bands which impinge as strip-like portions on the end area  42 . 
     Two images  43 ,  44  of strip-like portions, which illuminate a multiplicity of pixels  45  illustrated as dots, impinge on the end area  42 . The doubly traced circular line  6  is an imaginary representation of the cigarette paper  47  surrounding the cigarette head  41 . The images  43 ,  44  have a central portion  48  and  49 , respectively, which corresponds to the tobacco-side end area regions illuminated by the respective strip-like portions. These central portions  48 ,  49  are bounded by in each case two point-like end portions  50  to  53 . These point-like end portions  50  to  53  correspond to bright light spots at the locations at which the strips of light impinge on the filter paper. 
     FIG. 4 c  shows the image generated or calculated by an evaluation device. This image need not necessarily be displayed. It is sufficient for the data on which this image is based to be calculated in order to implement the invention. A respective centroid line  54 ,  55  is determined from the central portions  48 ,  49 . The centroid lines  54 ,  55  are advantageously calculated in such a way that they lie parallel to one another. In addition, the end portions  50  to  53  are each combined to form a centroid  56  to  59 . 
     FIG. 5 a  shows a cigarette which is too short by comparison with the cigarette illustrated in FIG. 4 a . The cigarette illustrated in FIG. 5 a  is shorter by the distance A than the cigarette illustrated in FIG. 4 a . As a result of this, the central portions  48 ,  49  illustrated in FIG. 5 b  are closer together than those illustrated in FIG. 4 b . The same applies to the end portions  50  to  53 . This is a consequence of the light bands which run toward one another with increasing distance and lead to the portions being moved closer together. 
     The same applies correspondingly to the centroid lines  54 ,  55  and centroids  56  to  59  illustrated in FIG. 5 c . This displacement results in a shorter distance C in FIG. 5 c  than a corresponding larger portion B in FIG. 4 c.    
     FIG. 6 a  again shows the cigarette head  41  of a filterless cigarette, in which, however, some of the tobacco filling is missing. This leads to a hole  60 . Therefore, in the image  43  of an upper strip of light on the detector, which image encompasses an upper portion of the end of the cigarette head  41 , an irregularity is discernible in the upper central portion  48  in FIG. 6 b . This is because the central section  48  of the image  43  is not oriented essentially horizontally but rather slopes away to the side. FIG. 6 c  shows the centroid lines  54 ,  55  calculated from this. The centroid line  54  illustrated in FIG. 6 c  is displaced toward the center of the cigarette by comparison with the centroid line  54  illustrated in FIG. 4 c . This is a consequence of the hole  60 . Since the lower image  44  in FIG. 6 b  corresponds to that illustrated in FIG. 4 b , the centroid line  55  in FIG. 6 c  is at the same position as in FIG. 4 c . The distance between the centroid lines  54 ,  55  now no longer corresponds to the desired distance B in accordance with FIG. 4 c , but rather is smaller than said desired distance. A defective cigarette can be inferred from this. A further special feature of the illustrations in accordance with FIGS. 6 b  and  6   c  emerges from the fact that the intrinsically slanted portion  48  is converted into a straight centroid line  54 . This orientation—compelled computationally—of the centroid lines serves for determining the distance between the centroid lines  54  and  55  more simply. 
     FIG. 7 a  shows the cigarette head  61  of a recessed filter cigarette with a filter piece  62  and a hollow tip  63 . The strips of light which impinge as strip-like portions on the cigarette head  61  are represented as images  64 ,  65  on the detector  32  in accordance with FIG. 7 b . In the case of such a correctly formed cigarette, central portions  66 ,  67  are situated in a manner displaced toward the cigarette axis. The end portions  50  to  53 , by contrast, are located at the same position as in FIG. 5 b  for a completely filled cigarette. 
     FIG. 7 c  shows calculated centroid lines  68 ,  69 , which, in the case of a proper recessed filter cigarette, are at a distance which is less than the distance C illustrated in FIG. 4 c . In addition, the centroids  56  to  59  in FIG. 7c are situated at a horizontal position that differs from that of the centroid lines  68 ,  69 . This is due to the fact that the light bands or strip-shaped portions which impinge on the cigarette head  61  are displaced toward the cigarette axis, since these portions are set back in the axial direction, that is to say are at a greater distance from the inspection apparatus. 
     FIG. 8 a  once again shows a cigarette head  61  of a recessed filter cigarette, in which case, however, the filter  62  is formed defectively since it has been obliquely clipped. As a result, the central portions  66 ,  67  of the images  64 ,  65  are situated at a different position in FIG. 8 b  compared with FIG. 7 b . However, the end portions  50  to  53  of the images  64 ,  65  are situated at the same position as in FIG. 7 b . FIG. 8c shows the centroid lines  68 ,  69  produced from the images in accordance with FIG. 8b, and also the centroids  56  to  59 . The centroids  56  to  59  are not displaced relative to FIG. 7 c , whereas the centroid lines  68  and  69  in FIG. 8 b  are displaced upward compared with FIG. 7 c . In addition, they are at a smaller distance from one another. 
     The differentiation between centroid lines  54 ,  55  to  68 ,  69  and centroids  56  to  59  makes it possible to ascertain one or four reference points on the edge of the cigarette casing or tip sleeve. As a result, it is possible to make statements about set-back filters or holes in the tobacco even in a quantitative manner, that is to say that statements can be made about distances between the end edge of a cigarette and possible holes or the depth of a tip sleeve in the case of recessed filter cigarettes or Papyrossi cigarettes. By way of example, it is possible to verify by measurement whether a tip sleeve having a setpoint depth of 5 mm lies within tolerance limits of ±1 mm. 
     The inspection method described and also the inspection apparatus described allow a very high measurement accuracy. Furthermore, a snapshot of a cigarette head or of the cigarette heads of a cigarette formation suffices for inspecting the length of a cigarette, the depth of a tip sleeve, the form of a cigarette head and also the filling with tobacco or filter. As a result, a cigarette head can be measured in one motion. As a result—unlike in other known inspection methods in which, by way of example, a plunger is pressed onto a cigarette head—this contactless method enables a cigarette packaging or production machine to be operated at high speed. The invention therefore opens up a host of possibilities for the inspection of cigarette heads.

Technology Category: 1