Abstract:
A wrapped-product quality control method and a wrapped-product packing method include providing a wrapped product including a product in a wrapper; supplying the wrapped product on a measuring background in a capture range of an infrared-sensitive imaging device, the product having a product temperature different from a measuring background temperature of the measuring background, and the wrapper having a wrapper temperature; capturing with the infrared-sensitive imaging device infrared radiation from the wrapped product and the measuring background; providing an image of the product or of the wrapped product from the infrared radiation captured with the infrared-sensitive imaging device; and analyzing the image for quality control of the wrapped product. A corresponding wrapped-product quality control device and a corresponding wrapped-product.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to wrapped-product quality control and packing methods, and wrapped-product quality control and packing devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    Generally products, like ice creams, can be packed in a wrapper, such as a plastic or paper-like sheet or box. One or a multiple of such wrapped products may be packed in a packing container, like a cardboard box or a flexible bag. When producing the product, or during its wrapping or transport the product may become damaged or otherwise not satisfy certain quality standards with respect to its appearance or integrity. A wrapper may even not contain a product. One therefore likes to do a quality check of the wrapped product, which can be done just before packing the wrapped product into a packing container, or can be combined with packing into the packing container. When the product concerns an ice cream, for instance, it might be cracked or broken into parts. In case of an ice cream on one or more sticks, such stick may not be inserted properly into the ice cream, it may be broken, or stick out of the wrapper. One likes to prevent such wrapped products of insufficient quality from being packed in a packing container and shipped for sale. However, such an integrity check for quality control purposes is not readily available. 
       SUMMARY OF THE INVENTION 
       [0003]    It is therefore an aim of the invention to provide a quality control method that can be easily integrated in the handling process of wrapped products by providing a wrapped-product control method comprising providing a wrapped product comprising a product in a wrapper; supplying said wrapped product on a measuring background in a capture range of an infrared-sensitive imaging device, said product having a product temperature different from a measuring background temperature of said measuring background, and said wrapper having a wrapper temperature; capturing with said infrared-sensitive imaging device infrared radiation from said wrapped product and said measuring background; providing an image of said product and/or of said wrapped product from said infrared radiation captured with said infrared-sensitive imaging device; and analysing said image for quality control of said wrapped product. 
         [0004]    Part of the wrapper not in contact with the product will generally have a temperature not equal to the product, which causes such part of the wrapper to radiate infrared radiation having certain spectral distribution that is different from a spectral distribution of infrared radiation radiated by the product and part of the wrapper in contact with the product. The method allows discriminating the product from its wrapper and therefore a view on an image of the product so that the product can be quality checked. 
         [0005]    On the other hand the spectral distribution of infrared radiation radiated from said product and its wrapper can both be different from the measuring background, which allows discriminating product and wrapper from the background and therefore a view on a combined image of product and wrapper for a further quality check of the wrapped product. 
         [0006]    In an advantageous embodiment of the wrapped-product control method said wrapped product is supplied on a conveyer, said conveyer providing said measuring background. The wrapper will be in contact with the conveyer and the surroundings thereof, and the part of the wrapper not in contact with the product will take the temperature of the conveyer to provide a temperature difference between such part of the wrapper and the product for a good discrimination of product from wrapper. 
         [0007]    In another advantageous embodiment said wrapped product is supplied by a conveyer with an open structure over a measuring surface having a temperature different from said product temperature and different from a temperature of said conveyer, said measuring surface providing said measuring background through said open structure of said conveyer. When provided onto the measuring surface from the conveyer, part of the wrapper not in contact with the product will still have or be close to the temperature of the conveyer. Measuring surface, part of the wrapper not in contact with the product, and the product will have different temperatures and will thus radiate infrared radiation with different spectral distributions. They can therefore be easily discriminated from one another. 
         [0008]    In yet another advantageous embodiment said step of supplying said wrapped product is performed shortly after said product has been wrapped in said wrapper such that said wrapper temperature is different from said product temperature. This allows an straightforward discrimination of product and wrapper due to their temperature difference. Having a short time period between wrapping and measuring results in the wrapper end the product having different temperatures, which makes the discrimination easier. 
         [0009]    In a preferred embodiment of the wrapped-product control method said step of providing said image comprises dividing an area captured by said infrared-sensitive imaging device into a two-dimensional matrix of pixels; assigning a pixel temperature to each pixel based on a measured distribution of infrared radiation associated with said pixel; selecting a threshold temperature in between said product temperature and said wrapper temperature or in between said wrapper temperature and said measuring background temperature, said product temperature being in a product temperature range that at one end is delimited by said threshold temperature; selecting pixels having an associated pixel temperature being in said product temperature range; and building said image from said selected pixels. Such embodiment provides an efficient and reliable manner or providing images of the product or the wrapped product for quality control purposes. 
         [0010]    In yet another preferred embodiment said step of analysing comprises comparing said image with a reference image. Such embodiment provides an efficient and reliable manner of analysing the image for the intended quality control purposes. 
         [0011]    In another aspect the invention provides a wrapped-product packing method for packing a wrapped product into a packing container, said method comprising the wrapped product quality control method according to the invention; packing said wrapped product into said packing container when said wrapped product has passed said quality control; and rejecting said wrapped product when said wrapped product has failed said quality control. Performing the wrapped-product quality control method as part of a wrapped-product packing method guarantees that the packed wrapped products have passed the quality control test. 
         [0012]    In an advantageous embodiment said step of rejecting said wrapped product comprises removing said wrapped product. 
         [0013]    In another advantageous embodiment said step of packing said wrapped product comprises using a handling device to provide said wrapped product into said packing container, for instance, a gripping device for picking up said wrapped product. 
         [0014]    In yet another advantageous embodiment said step of packing said wrapped product comprises localizing said wrapped product using said infrared-sensitive imaging device. Such embodiment efficiently employs the infrared-sensitive imaging device both for quality control and for localizing purposes. 
         [0015]    In yet another aspect the invention provides a wrapped-product quality control device for quality control of a wrapped product, said wrapped product comprising a product in a wrapper, said device comprising an infrared-sensitive imaging device configured and arranged for capturing infrared radiation from a wrapped product on a measuring background, said product having a product temperature different from a measuring background temperature of said measuring background, and said wrapper having a wrapper temperature; and a computer configured and arranged for providing an image of said product or of said wrapped product from said infrared radiation captured with said infrared-sensitive imaging device, and for analysing said image for quality control of said wrapped product. Such device is capable to perform the wrapped-product quality control method according to the invention. 
         [0016]    In an embodiment providing an image of said product comprises dividing an area captured by said infrared-sensitive imaging device into a two-dimensional matrix of pixels; assigning a pixel temperature to each pixel based on a measured distribution of infrared radiation associated with said pixel; selecting a threshold temperature in between said product temperature and said wrapper temperature or in between said wrapper temperature and said measuring background temperature, said product temperature being in a product temperature range that at one end is delimited by said threshold temperature; selecting pixels having an associated pixel temperature being in said product temperature range; and building said image from said selected pixels. 
         [0017]    In a further embodiment analysing said image comprises comparing said image with a reference image. 
         [0018]    In an advantageous embodiment the wrapped-product quality control device comprises a conveyer for conveying said wrapped product, said conveyer providing said measuring background. 
         [0019]    In another advantageous embodiment the device comprises a conveyer with an open structure for conveying said wrapped product, said conveyer providing said wrapped product over a measuring surface having a temperature different from said product temperature and different from a temperature of said conveyer, said measuring surface providing said measuring background through said open structure of said conveyer. 
         [0020]    In yet another aspect the invention provides a wrapped-product packing device for packing wrapped products into a packing container, said device comprising the wrapped product quality control device according to the invention; a packing station for packing wrapped products that have passed said quality control of said wrapped product quality control device into said packing container. Such device is capable to perform the wrapped-product packing method according to the invention. 
         [0021]    In an advantageous embodiment the wrapped-product packing device comprises a removing mechanism for removing a wrapped product that has not passed said quality control of said wrapped product quality control device. 
         [0022]    In another advantageous embodiment said packing station and/or said removing mechanism comprises a handling device for handling said wrapped product, for instance, a gripping device constructed and arranged for picking said wrapped product. 
         [0023]    In yet another embodiment said wrapped-product packing device is configured and arranged such that said handling device comprises a gripping device configured and arranged for picking up said wrapped product based on a position of said wrapped product determined using said infrared-sensitive imaging device. 
         [0024]    In embodiments of the methods and devices according to the invention, said product is a frozen product. 
         [0025]    In other embodiments of the methods and devices according to the invention, said frozen product is an ice cream. 
         [0026]    In yet other embodiments of the methods and devices according to the invention, said wrapper is a non-metallic wrapper. A non-metallic wrapper generally has a low heat conduction and therefore will not easily take the temperature of the product, which allows a more straightforward discrimination of wrapper and product. 
         [0027]    In yet other embodiments of the invention said wrapper is a metallic wrapper, which may have advantageous properties for containment purposes of the product within the wrapper. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Further features and advantages of the invention will become apparent by a description of the invention by way of non-limiting and non-exclusive embodiments. Embodiments of the invention will be described with reference to the accompanying drawings, in which same reference symbols indicate like or same parts, and in which 
           [0029]      FIG. 1   a  shows an ice cream on a stick within a wrapper, the ice cream not presenting any integrity or other quality defects; 
           [0030]      FIG. 1   b  shows an image of the ice cream and its stick shown in  FIG. 1   a  as determined using infrared radiation measured with an infrared imaging device; 
           [0031]      FIG. 1   c  shows an image of the wrapped ice cream of  FIG. 1   a  as determined using infrared radiation measured with an infrared imaging device; 
           [0032]      FIGS. 2   a ,  2   b  and  2   c  correspond to  FIGS. 1   a,    1   b  and  1   c,  respectively, but present a defective ice cream in two pieces; 
           [0033]      FIGS. 3   a ,  3   b  and  3   c  correspond to  FIGS. 1   a,    1   b  and  1   c,  respectively, but present a defective ice cream having a stick that is connected to the ice cream at a wrong angle; 
           [0034]      FIGS. 4   a ,  4   b  and  4   c  correspond to  FIGS. 1   a,    1   b  and  1   c,  respectively, but present a defective ice cream missing a part;  FIGS. 5   a ,  5   b  and  5   c  correspond to  FIG. 1   a,    1   b  and  1   c,  respectively, but present a defective ice cream having a broken stick; 
           [0035]      FIGS. 6   a ,  6   b  and  6   c  correspond to  FIGS. 1   a,    1   b  and  1   c,  respectively, but present a defective wrapped ice cream having the stick sticking out of the wrapper; 
           [0036]      FIG. 7  shows a wrapped-product packing device having a wrapped product quality control device, both according to the invention; 
           [0037]      FIGS. 8   a  and  8   b  show diagrams of product, wrapper, measuring background and threshold temperatures, and a product temperature range; and 
           [0038]      FIG. 9  shows an image of an ice cream in a wrapper with the threshold temperature set close to the temperature of the ice cream. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0039]    A product in the form of an ice cream  11  on a stick  12  is shown in  FIG. 1   a.  The figure shows the ice cream to have one stick, but it may also be an ice cream on a double stick or an ice cream without a stick. The ice cream  11  is wrapped in a wrapper  13 . In the embodiment shown the wrapper is a non-metallic plastic wrapper in the form of a bag. However, the wrapper may also take the form of a box, such as a carton or plastic box. The ice cream in its wrapper provides a wrapped ice cream  10 . In general, it provides a wrapped product  10 . In the embodiment shown, the ice cream  11  has a length LI and a width WI, and its stick  12  has a length LS. The wrapper  13  has a length LW and a width WW. In the remainder of the description the product or ice cream is referred to by reference symbol  11 . However, the ice cream product  11  may also include the stick  12 , which should be apparent from its context.  FIGS. 2   a ,  3   a ,  4   a ,  5   a  and  6   a  show defective wrapped ice creams  10 . In  FIG. 2   a  the ice cream is cracked or broken into two parts, and shows a crack  11   a.  The ice cream of  FIG. 3   a  has its stick  12  connected at a wrong angle. In  FIG. 4   a  the ice cream shows missing part  11   b.  The stick  12  of the ice cream of  FIG. 5   a  is broken into two parts, having a broken off part  12   a.  In  FIG. 6   a  the ice cream is erroneously wrapped and has its stick  12  sticking out off its wrapper  13 . One likes to recognize such defective wrapped products and prevent them from shipping for sale. 
         [0040]      FIG. 7  shows a wrapped-product packing apparatus or device  101  having a wrapped-product quality control apparatus or device  100  and a packing station  200 . Without packing station  200  the figure would only show a wrapped-product quality control apparatus or device  100 . Quite a few, but not all wrapped ice creams (wrapped products) are identified by reference symbol  10  in  FIG. 7 . 
         [0041]    The wrapped-product quality control device  100  of the wrapped-product packing device  101  comprises infrared-sensitive imaging devices or cameras  110 ,  111 . Such imaging devices  110 ,  111  are capable of location-resolved detecting infrared radiation radiated by wrapped products  10  and their surroundings. The embodiment is shown to have two infrared-sensitive imaging devices  110 ,  111  mainly for illustrative purposes, although it may have two such imaging devices in practice. A practical embodiment can also have only one such imaging device or even more than two of such imaging devices. A signal generated by the imaging devices  110 ,  111  is passed over connecting lines  110   a,    111   a  to a computer  115  for further processing and handling. 
         [0042]    Wrapped ice creams  10  are transported by a conveyer  120  and are passed underneath the imaging devices  110 ,  111  in a conveying direction  120   a.  In the embodiment shown, the conveyer comprises a conveying belt  122  with an open structure in the form of a web or plurality of strings made of rubber or plastic (or any other applicable material) and presenting openings in the web or in between the plurality of strings. The conveying web or plurality of strings  122  are passed over rollers (not shown) for guidance and exerting a driving force. The wrapped ice creams are supported by the conveying web or plurality of strings. 
         [0043]    In an alternative embodiment the conveyer may comprise a conveyer belt with a closed surface. Preferably such belt with a closed surface has a low thermal conductivity to provide a good measuring background having a temperature that differs from the wrapped ice cream, or any other wrapped hot or cold product. A belt of a silicone material can be employed for this purpose. 
         [0044]    The ice creams  11  are frozen and will therefore be colder than the packing device  101  and the surroundings thereof. The part of the wrapper  13  not in direct contact with the ice cream will generally be warmer than the ice cream since it will have been heated due to contact with the conveyer  120  and the surrounding air. Infrared radiation radiated by the wrapped ice cream  10  will be detected by infrared-sensitive imaging device  110  when the wrapped ice cream comes into the capturing range  110   b  of imaging device  110 . The imaging device detects infrared radiation within its capturing range in a location-resolved manner and can therefore separately detect such radiation radiated by the ice cream, its wrapper and the background of the ice cream, which represents a measuring background. For imaging device  110  the measuring background is given by the conveying web or plurality of strings and a plate  121  as part of the conveyer  120  below the conveying web or strings  122 . The web or strings and the plate  121  are at a surrounding temperature, which thus represents a measuring background temperature of the measuring background. 
         [0045]    The imaging devices  110 ,  111  divide their capturing ranges  110   b,    111   b  into a two-dimensional grid or matrix of pixels. Such array of pixels  17  is partly and schematically shown in  FIG. 1   b.  For each pixel  17  the imaging devices measure a distribution of infrared radiation radiated by an area associated with that pixel. An area having a certain temperature radiates infrared radiation according to a specific wavelength distribution of that radiation. The area radiates infrared radiation at a specific relative intensity at an associated wavelength interval in relation to intensities in other wavelength intervals, the intensity distribution being associated with the temperature of that area. 
         [0046]    Having measured the wavelength distribution of infrared radiation, one can therefore assign a temperature to the measured area and associated pixel  17 . A temperature can thus be assigned for each pixel in the capturing range of the imaging device. Such analysis and assignment of a temperature to each pixel is done by computer  115  to which signals corresponding to the measurements of the imaging device are passed over connecting lines  110   a,    111   a.    
         [0047]    Part of the wrapper will be positioned in between an imaging device and the ice cream during imaging. In case that part of the wrapper is in contact with the ice cream it will take the temperature of the ice cream. There be also be an isolating layer of air or another gas in between the ice cream and that part of the wrapper, which may cause that part of the wrapper to have a higher temperature than the ice cream. Especially in case of a non-metallic wrapper the infrared radiation of the ice cream will pass the wrapper and will be sensed by the imaging device. Since the ice cream will have a larger mass and volume than the part of the wrapper in between ice cream and imaging device, the infrared spectrum sensed will generally be dominated by the infrared radiation from the ice cream, so that it can be discriminated by the imaging device. 
         [0048]    In the analysis a threshold temperature TT is selected. Such a threshold temperature can be selected in between a temperature TP of the ice cream or product and a temperature TW of part of the wrapper not in between ice cream and imaging device and thus not in direct contact with the ice cream, or in between a temperature TW of part of the wrapper not in between imaging device and ice cream (and thus not in direct contact with the ice cream), which will be shortly referred to as the wrapper temperature TW, and a measuring background temperature TM of the measuring background. A product temperature range PTR can be defined such that it comprises the temperature of the ice cream TP and that the range at one end is delimited by the threshold temperature TT.  FIG. 8   a  shows a product temperature range PTR for a threshold temperature TT in between product or ice cream temperature TP and wrapper temperature TW.  FIG. 8   b  shows a product temperature range PTR for a threshold temperature TT in between wrapper temperature TW and measuring background temperature TM. For best results the wrapper  13  is a non-metallic wrapper, which does not screen the electromagnetic infrared radiation from the inside of the wrapper and does not easily take the temperature of the product  11 . 
         [0049]    In the analysis of the signal from imaging device  110  the threshold temperature TT is selected in between wrapper temperature TW and ice cream temperature TP. For the situation in capturing range  110   b  of imaging device  110  the wrapper temperature TW will be equal or almost equal to measuring background temperature TM. Pixels having an associated pixel temperature in the product temperature range PTR are selected by computer  115  and an image is build from such pixels. Such image will be representative of the ice cream.  FIGS. 1   b ,  2   b,    3   b,    4   b,    5   b  and  6   b  show such images and the various defects in the ice creams corresponding to  FIGS. 2   b ,  3   b ,  4   b  and  5   b  become nicely visible. Crack  11   a  may show in the image of  FIG. 2   b  when the separation between both parts of the ice cream is large enough. 
         [0050]    In distinguishing images of defective ice creams the computer can compare the image with a reference image  15   a  as represented by the image of a non-defective ice cream in  FIG. 1   a.  Such comparison and distinguishing methods by computer analysis are generally known and will not be further explained. The computer may also check on certain parameters of the images, such as the length LI of the ice cream  11 , the width WI of the ice cream and the length LS of the stick  12 .  FIG. 2   b  shows that the width WI 2  of the corresponding defective ice cream is larger than the width WI of the reference image  15   a,  and  FIG. 5   b  shows that the length LS 5  of the stick of the corresponding ice cream is shorter than stick length LS of the reference image  15   a.    
         [0051]    Having passed underneath imaging device  110  the wrapped products or ice creams  10  come into the capturing range  111   b  of imaging device  111 . In the area of capturing range  11  lb a measuring plate  130  is provided underneath the conveyer web or plurality of strings. The temperature of measuring plate  130  is set a temperature that is elevated with respect to the temperature of the conveyer. The measuring plate  130  provides the measuring background having a measuring background temperature of the measuring plate. Since the wrapped product  10  will only spend a relatively short time above measuring plate  130 , the wrapper  13  will not heat to the temperature of the measuring plate but substantially remain at the temperature of the conveyer before arriving above the measuring plate  130 . 
         [0052]    A same measurement and analysis as described for imaging device  110  can be done. However, since the ice cream temperature TP, wrapper temperature TW and measuring background temperature TM are different, a threshold temperature TT can now be selected in between TP and TW or in between TW and TM, as represented by both  FIGS. 8   a  and  8   b , respectively. The images of  FIGS. 1   b,    2   b,    3   b,    4   b,    5   b  and  6   b  can be derived by setting the threshold temperature TT in between TP and TW. Further, the images of  FIGS. 1   c,    2   c,    3   c,    4   c,    5   c  and  6   c  can be derived by setting the threshold temperature TT in between TW and TM. Since the threshold temperature for imaging device  111  can be set in between TP and TW and in between TW and TM, the imaging device  110  can be dispensed with in the embodiment shown in  FIG. 7 . 
         [0053]    The images of  FIGS. 1   c,    2   c,    3   c,    4   c,    5   c  and  6   c  correspond to the wrapped product or ice cream  10 . The images of  FIGS. 2   c ,  3   c ,  4   c  and  5   c  all are identical to the reference image  16   a  of the non-defective wrapped product in  FIG. 1   c.  The image in  FIG. 6   c  deviates from the reference image  16   a  in  FIG. 1   c  because the stick of the corresponding ice cream sticks out of the wrapper, which can be distinguished using computer  115  by comparing these images. 
         [0054]    Based on the analysis of computer  115  the wrapped ice creams corresponding to  FIGS. 2   a ,  3   a ,  4   a ,  5   a  and  6   a  fail the quality control and can be rejected in a next step so they will not be shipped for sale. The rejection step may comprise removing the wrapped product. 
         [0055]    Having passed imaging device  111  and its corresponding capture range  111   b  the wrapped ice creams  10  arrive at packing station  200 . The packing station comprises a handling device that is embodied as a gripper  210  for picking up wrapped ice creams from the conveyer  120  which have passed quality control. The gripper can locate the individual ice creams based on the location of the ice cream on the conveyer as determined using one or both imaging devices  110 ,  111  and the speed of the conveyer, all under the control of computer  115 . Gripper  210  is therefore connected to computer  115  by connecting line  210   a.    
         [0056]    Gripper  210  can pick up individual wrapped ice creams  10  for packing them into a packing container  20 , such as a cardboard box, that can hold a plurality of wrapped ice creams. After having picked up a wrapped ice cream the gripper is moved in direction  211  towards packing container  20 . Wrapped ice creams can be packed in the packing container in any known fashion, which will not be further described. 
         [0057]    Based on the location information of individual wrapped ice creams  10  and quality information on whether they have passed quality control or not, individual wrapped ice creams can be rejected at the packing station by not packing such wrapped ice creams into the packing container  20 . The gripper can pick up such rejected wrapped ice creams and move in direction  212  to provide them in a separate storage location or waste bin  220 . Gripper  210  may also ignore such rejected wrapped ice creams and have them moved further by conveyer  120  to a waste location or any other location for handling. Such rejected ice creams may be provided into a waste bin by dropping of the conveyer at the conveyer end, which is not shown in the drawings. 
         [0058]    In another embodiment the ice cream is wrapped in a metallic wrapper that may not pass (enough) radiation from the ice cream within the wrapper, so that the ice cream cannot be imaged as such. However, the wrapper of the wrapped ice cream will have a lower temperature when an ice cream is inside as compared to a situation in which no ice cream is contained within the wrapper. The wrapper will be cooled through direct contact with the ice cream or through radiation or convection. This allows identifying wrappers defective wrapped products in which no wrapper is contained within the wrapper form wrapped products having an ice cream within the wrapper. When no ice cream is contained within the wrapper, the wrapper will take the temperature of the surroundings and the measuring background TM. A threshold temperature TT is set in between the wrapper temperature TW of a wrapped ice cream and the measuring background temperature. Non-defective products are then identified and handled in a similar fashion as described above. 
         [0059]      FIG. 9  shows an image  16  of a wrapper in which an ice cream is contained. The threshold temperature is set close to a temperature of the ice cream so that an image of part of the wrapper closest to the ice cream is created. The wrapper temperature will generally increase in a direction moving away from the ice cream.  FIG. 9  also shows in dashed lines the contour of the ice cream  11  within the wrapper and of the wrapper  13 . No image will be created in case no ice cream is contained inside the wrapper. Such defective products can therefore not be localized by the infrared imaging devices. Conveyers with belts having either open or closed structures can be employed, as has been described earlier. 
         [0060]    When the threshold temperature is set at a higher temperature, an image filling the whole contour of the wrapper will be provided. Such image will comparable to the ones shown in  FIGS. 1   c,    2   c,    3   c,    4   c  and  5   c.  However, at setting a higher threshold temperature there is also a larger chance of labelling a defective product as a non-defective product. 
         [0061]    The invention has been described for wrapped ice creams, but can be employed as well for any other wrapped cold product or even any wrapped product of which the temperature differs from a temperature of the surrounding environment.