Abstract:
An inspection device and an inspection method for detecting foreign bodies in a filled container, and having at least one inspection camera, a transport device for the at least section-by-section linear transport of the container and at least one vibration device for vibrating the container, where foreign bodies in the containers can be set in motion without complicated acceleration and retarding of the container and the movements can be registered and compared as single images by the inspection cameras even with a stationary camera position. The construction of the device is less space-consuming and less complicated than for machines of the rotary type and the detection of foreign bodies is more reliable than with conventional machines of the linear type.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of priority of German Application No. 102009035585.5, filed Jul. 31, 2009. The entire text of the priority application is incorporated herein by reference in its entirety. 
       FIELD OF THE DISCLOSURE 
       [0002]    The disclosure relates to an inspection device and an inspection method for detecting foreign bodies in a filled container, such as in beverage bottling operations. 
       BACKGROUND 
       [0003]    During beverage bottling in containers, such as for example glass or plastic bottles, it may be necessary to inspect the filled and sealed containers for the presence of foreign bodies. Here, it is particularly difficult to detect small particles such as transparent glass splinters. Since the containers often have scuff marks or scratches on the bottom, glass splinters can often not be clearly identified. 
         [0004]    With regard to this problem it is known from WO 2004/053471 A1 that the content in the bottle can be set into motion on a first carousel by rotation followed by rapid retardation of the bottle and a dark field image of the bottle bottom is obtained from below while the bottle content is still in motion. The foreign bodies, which appear brightly in the image, can be acquired by stationary cameras or cameras which rotate with the bottle. Although devices of this nature can also detect small particles reliably, they are however very complex and space-consuming. In addition, they are only suitable for rotationally symmetrical bottles. 
         [0005]    In order to avoid the outlay in terms of apparatus and time for the rotation and retardation of the bottles to be inspected, DE 10 2004 051 961 A1 suggests that the bottle content is set into motion by a vibration device. However, this device is also designed as a rotary machine with infeed and discharge stars. Additionally, a camera is needed for each bottle position on the carousel. 
         [0006]    WO 02/01207 A1 describes an inspection device conceived for a straight-line configuration which rotates the containers in a belt station and then guides them past a row of cameras positioned at the side. These cameras supply triggered single images which are compared in an evaluation unit. However, it is difficult to quickly accelerate the bottles and retard them again and to guide them precisely in the belt station, which means that foreign matter cannot be detected with sufficient reliability and accuracy. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    Therefore, an aspect of the disclosure is to provide a compact inspection device with a high detection accuracy and simple construction as well as an appropriate inspection method. 
         [0008]    This is achieved with a device with at least one inspection camera, one transport device for at least section-by-section linear transport of the container and at least one vibration device for vibrating the container. 
         [0009]    Due to the fact that the container can also in particular be vibrated sideways in a linear machine, foreign bodies in the container are set into motion without complicated accelerating and retarding of the container. These foreign bodies can be registered in single images by the inspection camera even with a stationary camera position and detected by comparison of the images. In this way the space-consuming and complicated constructions usual with machines of the rotary type are not needed. The proportion of incorrect negative examination results is in comparison to conventional inspection devices noticeably reduced with the linear type. 
         [0010]    Preferably, the vibration device comprises at least one vibrator for producing vibrations and a circumferentially running transmission belt for transferring the vibrations to the container. This facilitates an effective transfer of vibrations to the container side wall moving past the vibrator. 
         [0011]    Preferably the vibrator is a motor with an unbalance. In this way vibrations can be generated in a simple and economic manner and optionally a plurality of vibrators can be combined in one vibration device. 
         [0012]    With a particularly favorable embodiment the vibration device comprises a slide rail and/or a roller unit which is in contact with the vibrator and the transmission belt. In this way the vibrator can be arranged stationary, vibrations transferred to the passing belt and the frictional forces acting on the transmission belt can be minimized. 
         [0013]    Preferably at least two vibration devices are provided which act on the container side wall from essentially opposite directions. In this way the transfer of vibrations to the container is particularly effective. 
         [0014]    In a particularly favorable embodiment the transport device comprises an upper and a lower pair of guide belts which hold the container off the ground in each case and the vibration device is set up such that it transfers vibrations to the container between at least one upper and one lower guide belt. In this way the vibration device can be integrated in a simple and space-saving manner in an off-floor transport device of the linear type. 
         [0015]    Preferably the guide belts have a damping effect on the vibration at an oscillation frequency of the vibration device. This prevents an unwanted transfer of the vibrations to the base frame of the inspection device. 
         [0016]    Preferably the inspection camera is arranged such that it can take dark-field images of the container bottom from below. This facilitates a particularly high contrast display of foreign bodies and ensures a defined optical examination plane. 
         [0017]    In a particularly favorable embodiment at least two inspection cameras are arranged one behind the other with respect to the transport direction of the transport device, whereby the image regions of the inspection cameras overlap. In this way a contiguous sequence of individual images can be produced, whereby changes on the container bottom during the comparison of the single images indicate moving foreign bodies. 
         [0018]    A preferred embodiment also comprises at least one illumination device, which irradiates the container sidewards below the vibration device, in particular below the transport device. In this way foreign bodies can be particularly effectively irradiated and rendered visible through beam deflection on the foreign bodies. 
         [0019]    Preferably the illumination device is a continuous light source. In this case the camera can be triggered independently of the light source in order to optimize the image acquisition. 
         [0020]    Preferably at least two illumination devices are provided which form a light corridor illuminating the container on both sides. The container bottom can in this way be particularly evenly illuminated. 
         [0021]    A particularly favorable embodiment comprises furthermore an evaluation unit for detecting the foreign bodies through the comparison of image data from the inspection camera and a diversion device for diverting faulty containers. In this way it can be ensured that only fault-free containers are processed further. 
         [0022]    The problem is furthermore solved by an inspection method comprising the following steps: a) at least section-by-section linear transport of the container; b) sideways vibration of the container to set the foreign bodies located on the container bottom in motion; and c) image-generating acquisition of light which has been deflected by the foreign bodies. 
         [0023]    Due to the fact that the containers are vibrated sideways in a linear machine, foreign bodies on the container bottom can be moved without complicated acceleration and retarding of the container and they can also be registered as single images and compared by inspection cameras even in a stationary camera position. In this way the space-consuming and complicated constructions usual with machines of the rotary type are not needed. 
         [0024]    Preferably, in step c) triggered single shots of the container bottom are taken in the dark field and the method also comprises the following step: d) evaluation of the acquired image data, whereby an evaluation region is assigned to the container bottom in the single shots in each case and image data from the assigned evaluation regions are compared with one another to detect foreign bodies as differences in the compared image data; and e) rejection of the container if at least one foreign body has been found in it. 
         [0025]    In this way a high contrast display of the foreign bodies is facilitated. In addition, the time required for the evaluation of the image data is reduced and thus the number of single images possible per inspection can be increased in favor of an improved detection probability and accuracy. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    A preferred embodiment is illustrated in the drawings. The following are shown: 
           [0027]      FIG. 1  a schematic plan view of an inspection device according to the disclosure; 
           [0028]      FIG. 2  a schematic cross-section through the device from  FIG. 1  along the sectional line A-A. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    As can be seen from  FIGS. 1 and 2 , the inspection device  1  according to the disclosure is designed as a linear machine with a linear transport section  2  and comprises a transport device  3  with an upper and a lower pair of guide belts  4   a,b  and  5   a,b , whereby abutments for the guide belts  4   a,b  and  5   a,b  in the region of the transport section  2  have been omitted for the sake of clarity and the associated deflection rollers are only indicated in  FIG. 1 . An additional pair of transmission belts  6   a,b  is provided between the guide belts  4   a,b  and  5   a,b , arranged essentially parallel to them and running together with them (hidden in the plan view by the upper guide belts  4   a,b ). The additional belts are a constituent part of a vibration device  7  with stationary vibrators  8  and slide rails  9  and they provide the transfer of vibration to the filled containers  10 , such as for example glass or plastic bottles, which are to be inspected. 
         [0030]    The guide belts  4   a,b  and  5   a,b  each hold at least one container  10  off the floor and transport it through a light corridor  11  consisting of two oppositely situated, sideward illumination units  13 , past inspection cameras  15 , which take dark-field images of the container bottom  10   a  or of foreign bodies  17  optionally present on it, such as for example glass splinters. 
         [0031]    The containers  10  are passed to the inspection device  1  via a first conveyor belt  18  and carried away by a second conveyor belt  19  and transferred to a diversion device  21 , such as a conventional pusher, for diverting faulty containers  10 . The device also comprises a control and evaluation unit  23  for controlling the cameras  15 , for evaluating the image data produced by the cameras  15  and for controlling the diversion device  21  on the basis of the inspection results. However, separate units can also be provided for this. 
         [0032]    The vibration device  7  is in contact with the container  10  on both sides and transfers the oscillations through the container wall  10   b  and optionally to foreign bodies  17  located on the container bottom  10   a , by means of which they are set in motion. The vibration device  7 , double-sided with regard to the transport direction, facilitates a particularly effective transfer of vibrations to the container  10 . However, it would also be possible to provide the vibration device  7  only on one side of the transport section  2 . The inspection device  1  is also suitable for rotationally unsymmetrical containers  10 , particularly for those with sectionally flat lateral faces  10   b , on which the transmission belts  6   a,b  can contact over a large area, such as for example as with an essentially rectangular container cross-section. 
         [0033]    The vibration device  7  is preferably supported vibration-damped on the inspection device  1  so that vibrations are selectively transferred to the container  10 . 
         [0034]    The vibration device  7  comprises at least one vibrator  8 , for example in the form of a motor with an unbalance, as well as a slide strip  9  and/or a roller mechanism  9 ′ (not illustrated) via which each of the transmission belts  6   a,b  runs under low friction. The slide strip  9  can for example be produced in a plastic with a low coefficient of friction, such as PTFE. The slide strips  9  or roller mechanisms  9 ′ and/or the vibrators  8  could be tensioned by a spring force and press the transmission belts  6   a,b  against the container  10  in order to ensure a good transfer of the vibration. It is also conceivable that the vibration transfer is improved by a (not illustrated) moistening device at the contact point between the transmission belts  6   a,b  and the container  10 . 
         [0035]    The vibrator  8  preferably produces frequencies in the range between 10 and 50 kHz, in particular between 20 and 40 kHz, preferably at 30 kHz. Frequencies above the audible frequency range are particularly advantageous. If required, vibrators  8  could also be combined with different frequencies. The number of vibrators  8  can deviate from the illustrated example. 
         [0036]    The transmission belts  6   a,b  are preferably produced from a material which transfers vibrations in the frequency range of the vibrator  8  particularly well to the container  10 . 
         [0037]    In contrast the guide belts  4   a,b  and  5   a,b  preferably contain a material which damps oscillations particularly well in the frequency range of the produced vibrations. Expediently, a damping layer can be provided on the belts  4   a,b  and  5   a,b , for example a foam layer, in particular on the side facing the container  10 . 
         [0038]    The illumination units  13  comprise for example a plurality of light emitting diodes arranged one behind the other in the transport direction and are arranged on both sides of the transport section  2  with preferably the same distance to the container  10 , in particular in the immediate vicinity of the container bottom  10   a . In order to irradiate particles  17  in the vicinity of the bottom particularly effectively, the illumination units  13  are preferably arranged below the lower guide belts  5   a,b . A position between the lower guide belts  5   a,b  and the transmission belts  6   a,b  would also be possible. 
         [0039]    With the illumination units  13  directed light of different wavelengths, e.g. infrared, can be coupled into the inside of the filled containers  10  through the container side wall  10   b . In the illumination units  13  a mixed arrangement of light-emitting diodes is conceivable, whereby single light-emitting diodes can be operated selectively with a certain wavelength according to the type of container and/or type of filling material. The illumination units  13  preferably emit continuous light in order to be able to acquire the image at any point in time. However, synchronous pulsed illumination units  13  are also conceivable with the cameras  15 . 
         [0040]    The cameras  15  are positioned such that the images of the containers  10 , held above the ground, can be taken from underneath. The cameras  15  are expediently focused on the container bottom  10   a  or on a region slightly above the container bottom  10   a  in which the foreign bodies  17  may be present. In the imaging beam path deflection mirrors (not illustrated) could be provided for sideward beam deflection, for example by 90°, so that the cameras  15  are not arranged directly below the transport section  2 , but are aligned to the side in order to prevent soiling and/or damage to the cameras  15 . 
         [0041]    The image areas of the cameras  15 , the number of which is not restricted to the illustrated example, overlap so that a contiguous sequence of single images of the container bottom  10   a  can be produced. To achieve this the cameras  15  are triggered by the control and evaluation unit  23  in a suitable manner. The image data can be acquired, for example, by a 4-to-1 frame-grabber with which four cameras  15  are connected to a common computing processor of the control and evaluation unit  23 . However, also just one camera  15  can be provided. 
         [0042]    The control and evaluation unit  23  evaluates only a part of the image data of a single shot, namely an evaluation region ROI (Region Of Interest) (not illustrated) assigned to the bottle bottom  10   a , for example around-shaped image section. This means that the control and evaluation unit  23  only searches in the evaluation region ROI for moving structures or foreign bodies  17 . This reduces the time required for the evaluation of a single shot and increases the number of possible shots per container inspection. In this way the probability that a light reflection on a foreign body  17 , such as indicated in  FIG. 2  by the dashed line L, can be registered or detected increases and thus too the accuracy or the reliability of the foreign body detection. 
         [0043]    With the inspection device according to the disclosure the following method can be employed: 
         [0044]    The filled containers  10  to be inspected are continuously fed from the first conveyor belt  18 , pass continuously one after the other above the floor through the linear transport section  2  and are subjected to vibrations in the kilohertz range by the vibration device  7 . Particles  17  in the vicinity of the bottom are set into motion by the oscillations and jump around on the container bottom  10   a . In doing this they deflect the sidewards incident light to the cameras  15  which take triggered images of the container bottom  10   a  which are passed on to the control and evaluation unit  23 . Here, image sections, in particular the evaluation regions ROI corresponding to the container bottom  10   a  of the camera images of a container  10  are compared to one another. Image differences in the evaluation region ROI are detected as moving particles and the faulty container  10  is diverted so that only fault-free containers  10  are passed for further processing. 
         [0045]    In comparison to rotary machines the device  1  according to the disclosure is significantly more compact and more economical. Also rotationally unsymmetrically shaped bottles can be inspected in this way. The detection of foreign bodies  17  is more accurate and more reliable than with conventional inspection devices of the linear running type.