Abstract:
An apparatus in spinning preparation for detecting foreign objects of plastics material, such as polypropylene bands, fabric and films and the like, in or among fibre flocks, for example, of cotton, that are being removed (opened) from bales of textile fibre, comprises a foreign object detector, which detector and the fibre flocks are movable relative to one another. The foreign object detector comprises a transmitter and a receiver for electromagnetic waves or rays and an evaluating device for distinguishing the foreign objects from the fibre flock. To produce an improved apparatus, a source of polarised light that cooperates with at least one detector device (camera) acts on the fibre material (fibre flocks, fibre flock web), the fibre material being irradiated, with light passing through light-coloured and/or transparent sheet-form foreign objects of plastics material, and the detector device is capable of distinguishing sheet-form from fibrous foreign objects on the basis of its resolution.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority from German Application No. 103 47 240.1 filed Oct. 10, 2003, the entire disclosure of which is incorporated herein by reference  
       BACKGROUND OF THE INVENTION  
       [0002]     The invention relates to an apparatus for use in spinning preparation for detecting foreign objects of plastics material, such as polypropylene bands, fabric and films and the like, in or among fibre material, especially fibre flocks, for example, of cotton. The fibre material may in particular, but not exclusively, be fibre flocks being removed (opened) from bales of textile fibre, during which process a foreign object detector and the fibre flocks are movable relative to one another, the foreign object detector comprising a transmitter and a receiver for electromagnetic waves or rays and an evaluating device for distinguishing the foreign objects from the fibre flocks.  
         [0003]     In a known apparatus (DE 36 44 535 A1), the fibre flocks are arranged in a loose pile on a moving conveyor belt. A transmitter for the electromagnetic waves or rays is arranged above the conveyor belt with the pile of fibre flocks. A receiver is located between the upper and lower belt regions. The material of the conveyor belt is a material that is permeable to electromagnetic waves or rays. The loose pile of flocks is then irradiated. The foreign objects are often polypropylene bands. The apparatus enables the form (shape) colour, size or brightness of foreign objects to be determined. The recognised outwardly differing features of the foreign objects are used to differentiate them, by a comparison process, from the good fibres of the fibre flocks.  
         [0004]     It is an aim of the invention further to improve the apparatus for detecting foreign objects of plastics materials, such as polypropylene bands, fabric and films, and the like.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention provides a detection apparatus for detecting foreign objects of plastics material in or amongst fibre material, comprising 
        a source of polarised light;     a transport arrangement for so transporting the fibre material that it is irradiated by the source; and     a detector device arranged to receive light from the fibre material.        
 
         [0009]     The measures according to the invention enable a reliable detection of light-coloured or transparent plastics foreign objects that are responsive to polarised light to be achieved. It is advantageous therein that in particular those foreign objects having only a slight optical contrast with the good fibres (textile fibres) can be detected. The plastics materials occur in many cases in the form of packaging films or packaging fabrics. According to the invention, not only relatively large parts but also foreign fibres are recognised and detected.  
         [0010]     The foreign objects of plastics material may be able to rotate the polarisation vector of the polarised light. The light may be linearly polarised, circularly polarised, or elliptically polarised. The light source and the detector device may be arranged on different sides of the fibre flocks (transmitted light arrangement). The light source and the detector device may be arranged on the same side of the fibre flocks (incident light arrangement). Depolarisation may be effected for detection. Reflection-suppression may be effected for detection. Foreign objects of plastics material may change the polarised light by anisotropies (such as double refraction) such that the light is rendered visible by the analyser of the detector device. The fibre material may be arranged in a channel of glass or the like. The fibre material may be conveyed through a channel pneumatically. The fibre material may be arranged on a conveyor belt. The fibre material may be arranged with a roller, e.g. detaching roller.  
         [0011]     The roller may rotate rapidly. There may be provided a background that is diffuse; reflecting, for example, mirror-like; or luminous. The detector device may be a line-scan camera. The detector device may be a matrix camera. The detector device may comprise light sensors. Detection may take place in colour. Detection may take place in black and white. A polariser may be arranged between light source and fibre material. A light source that emits polarised light may be present. A polariser may be integrated on or within the light source. An analyser may be arranged between the fibre material and the detector device. A detector that also acts as analyser may be present. The analyser may be integrated on or within the detector. Light-refracting elements, for example prisms, may be arranged in the ray path. In addition or instead, lenses may be arranged in the ray path.  
         [0012]     A device for removing foreign objects may be arranged downstream of the evaluating device. The evaluating device and the removal device may be electrically connected with one another by a control or switching device. The device may be arranged downstream of a bale opener. The device may be arranged in or downstream of a cleaning device. The device may be arranged in or downstream of a carding machine. The device may be arranged in or downstream of a foreign fibre separator. The device may be arranged in or downstream of a foreign object separator.  
         [0013]     Anisotropies such as the double refractive effect of the foreign objects may be used for detection. Selectively absorbing behaviour (dichroism) of the foreign objects may be used for detection. Optically active behaviour (rotary dispersion) of the foreign objects may be used for detection. The detector device is advantageously able to distinguish sheet-form from fibre-form foreign objects on the basis of its resolution.  
         [0014]     The invention also provides an apparatus in spinning preparation for detecting foreign objects of plastics material, such as polypropylene bands, fabric and films and the like, in or among fibre flocks, for example, of cotton, that are being removed (opened) from bales of textile fibre, during which process a foreign object detector and the fibre flocks are movable relative to one another, the foreign object detector comprising a transmitter and a receiver for electromagnetic waves or rays and an evaluating device for distinguishing the foreign objects from the fibre flocks, characterised in that a source of polarised light that cooperates with at least one detector device (camera) acts on the fibre material (fibre flocks, fibre flock web), the fibre material being irradiated, with light passing through light-coloured and/or transparent sheet-form foreign objects of plastics material, and the detector device being capable of distinguishing sheet-form foreign objects from fibrous plastics items (synthetic fibres). 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic side view of a carding machine with a first embodiment of apparatus according to the invention;  
         [0016]      FIG. 2  shows the first embodiment on the carding machine according to  FIG. 1  with the fibre web to be examined;  
         [0017]      FIG. 3  is a schematic side view of a second embodiment of apparatus according to the invention on a cleaner, associated with the removed fibre material;  
         [0018]      FIG. 4  is a schematic side view of a further embodiment of the invention associated with a high-speed roller of a cleaner with a pneumatic foreign object separation device;  
         [0019]      FIG. 5  is a schematic side view of a further embodiment on a foreign object recognition and separation device with a high-speed roller;  
         [0020]      FIG. 6  is a front view of an embodiment of the invention associated with a transport channel and having a transmitted light arrangement;  
         [0021]      FIG. 7  is a side view of an embodiment of the invention associated with a transport channel and having an incident light arrangement;  
         [0022]      FIG. 8  is a side view of a variant of the apparatus of  FIG. 7  in which the polariser and the analyser are combined in one component;  
         [0023]      FIG. 9  shows a further variant of the embodiment of  FIG. 7  with two cameras; and  
         [0024]      FIG. 10  shows a further embodiment with two cameras. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]      FIG. 1  shows a carding machine, for example, a TC 03 Card made by Trutzschler GmbH &amp; Co. KG of Mönchengladbach, Germany, with feed roller  1 , feed table  2 , licker-ins  3   a,    3   b,    3   c,  cylinder  4 , doffer  5 , stripping roller  6 , squeezing rollers  7 ,  8 , web-guide element  9 , web funnel  10 , take-off rollers  11 ,  12 , revolving card top  13  with guide rollers  13   a,    13   b  and card flat bars  14 , can 15  and can coiler  16 . The directions of rotation of the rollers are shown by curved arrows. The letter M denotes the midpoint (axis) of the cylinder  4 .  4   a  denotes the clothing and  4   b  the direction of rotation of the cylinder  4 . The letter C denotes the direction of rotation of the revolving card top  13  in the carding position and the letter D denotes the return transport direction of the card flat bars  14 . Beneath the stripping roller  6  there is arranged a stationary supporting and guiding member  17 ; the upper squeezing roller is arranged in close proximity to the stripping roller  6 . The directions of rotation of the cylinder  4  and the rollers are represented by respective curved arrows. The supporting and guiding member serves to receive the apparatus  18  according to the invention. The letter A denotes the working direction.  
         [0026]     In  FIG. 2 , the reference number  21  denotes the region in which the removed fibre web  19  passes from the stripping roller  6  to the squeezing rollers  7 ,  8 . The supporting and guiding member  17  has essentially a four-cornered cross-section. The upper surface is slightly concavely curved. The radius of curvature of the curve of the upper surface is greater than the radius of curvature of the stripping roller  6 . The arrow A indicates the running direction of the fibre web  19 . The element  17  is in the form of a housing, a transparent window  20  being provided in the sliding contact region. The fibre web  19  is located initially on the clothing of the doffer  5 , is guided in the roller nip between doffer  5  and stripping roller  6  around and over the clothing  6 a of the stripping roller  6 , is detached from the stripping roller  6  a little way after the region of the perpendicular diameter, is guided in the region of the window  20  in direction A, following the end region runs completely freely and finally enters the roller nip between the squeezing rollers  7 ,  8  and passes between these. The upper surface of the element  17  faces towards the clothing  6   a  of the stripping roller  6 . With its one end region, the element  17  is associated with the roller nip between doffer  5  and stripping roller  6 . The other end region is arranged in the region between stripping roller  6  and squeezing rollers  7 ,  8 , the edge thereof being aligned in the direction towards the roller nip between the squeezing rollers  7 ,  8 . The element  17  is an extruded profile, for example, of aluminium, with an inner cavity  17   a.  Fixed cameras  21   a  to  21   1 , for example, diode matrix cameras, an illuminating device  22  arranged to generate polarised light, (for example, comprising several light-emitting diodes), and a reflecting mirror  23  are arranged in the inner cavity  17   a  of the housing  17 . The reflecting mirror  23  is arranged at an angle between the objective of the cameras  21   a  to  21   1  and the illuminating device  22  on the one hand and the inside of the window  20  on the other hand. The fibre web  19  runs over the outside of the window  20  in direction A. The window  20 , for example of glass, is kept clean by contact with the moving fibre material. The cameras  21   a  to  21   1  (only camera  21   a  is shown in  FIG. 2 ) are arranged on a common support  24 , which is secured to the element  17 . The reference numeral  25  denotes an electrical lead. The reference numeral  26  denotes an electronic evaluating unit to which the display device  27  and/or a separating device  28  (see  FIGS. 4 and 5 ) are connected. The reference numeral  52  denotes the machine control for the card (see  FIG. 1 ).  
         [0027]     In the arrangement of  FIG. 3 , an apparatus  18  according to the invention is mounted on a cleaning machine  30 , e.g. a CLEANOMAT VCT 3 cleaning machine made by Trüitzschler GmbH &amp; Co. KG. The apparatus  18  is associated with the fibre tuft material  33 , e.g. cotton, removed by the last roller  31   c —viewed in the working direction B—of the multiple roller cleaner  30  and discharged through a pipeline  32 . The apparatus  18  is connected to the machine control system and allows unwanted polypropylene foreign objects in the cotton fibre material to be detected.  
         [0028]     Referring to  FIG. 4 , an apparatus  18  according to the invention and a pneumatic foreign object separation device  34  are associated with the middle roller  31 b of the cleaner  30 , viewed in the direction of rotation  31 ′ of the roller  31   b.    
         [0029]     In the arrangement of  FIG. 5 , the apparatus  18  according to the invention is associated with the high-speed roller  36  of a foreign object recognition and separation device  37 , e.g. a SECUROMAT SCFO device made by Trützschler GmbH &amp; Co. KG. Viewed in the direction of rotation of the roller  30 , downstream of the device  37  there is arranged a pneumatic foreign object separating device  34 , which comprises a plurality of blast nozzles  38  across the width of the machine  37 . The machine control system ( 52 , see  FIG. 2 .) to which the apparatus  18  according to the invention and the device  34  are connected, always functions in response only to one nozzle  38   a  to  38   n  or to two adjacent nozzles  38   a  to  38   n,  in the operative region of which the foreign object  35  has been detected. As a consequence, only a few fibre tufts (only 1-2 g) of cotton per separation process are removed. This permits a selective, sensitive adjustment of the system to enable even small portions to be separated out without allowing an unduly high loss of fibre material. The foreign objects  30  and the fibre material are located on the roller  36 , which has a saw-tooth or needle clothing.  
         [0030]      FIG. 6  shows an arrangement in which an apparatus of the invention is associated with a glass channel  40 , the apparatus being operable as a transmitted light arrangement: the light radiating from a light source  4  is converted by means of a polariser  42  into linearly, circularly or even elliptically polarised light. This shines through the material to be inspected that is being transported through the transparent channel  40  through the optical arrangement. Whereas with cotton  43  and other natural constituents of the cotton  43  there is no change in the light, the plastics foreign object  44  produces a change in the plane of polarisation of the light. This change can be rendered visible by means of the analyser  45 . Contrast differences and colour shifts occur relative to the other good material. These are picked up by one or more detectors  46  (a camera in  FIG. 6 ) and processed by an associated evaluating unit  47 , so that an automatic separation (not shown) of the detected plastics items  44  can be carried out.  
         [0031]      FIG. 7  shows an arrangement which is the same, in principle, as  FIG. 6 , except that an incident light arrangement is used. The essential difference is that both illuminating means  41  and detector  46  (a camera in  FIG. 7 ) are situated on the same side of the material. The material is also separated here from the measuring arrangement by a window. The background  48  can be provided both by conveyor belts or rollers, which simultaneously serve to transport the material, and by fixed surfaces with lamps or surfaces with diffuse and shiny to mirror-like reflecting properties. Depending on the background used, the evaluation has to be effected differently, the important factor being that there is always an assessable change in light intensity or colour between cotton material  43  and the plastics items  44 . Depending on the evaluating method used, a contrast between background  48  and the material can be present/desirable or not.  
         [0032]     A further modification of the arrangement of  FIG. 7  is illustrated in  FIG. 8 . Here, the elements polariser  42  and analyser  45  are combined in one component  51 . Here too, surfaces of diffuse or shiny to reflective construction come into consideration as the background.  
         [0033]     Yet other embodiments comprise working with one or more pairs of cameras/detectors, the cameras of the or each pair being directed directly onto the same spot in the flow of material, as illustrated in  FIG. 9 . One camera  46  is equipped with an analyser  45 , which is arranged so that the analyser  45  suppresses reflection. The other camera  49  of the pair does not need this analyser  45  and is spatially arranged so that a maximum light reflection occurs with plastics films. Both cameras  46  and  49  are aligned with respect to one another so that they both take exactly the same image section. Even if the cameras are not aligned, however, this can be created by a calibration in the evaluating unit. In the evaluation, both images of the spatially identical scene (one with and one without light reflection) are now assessed by comparison after a previously possible signal conditioning. One option for this would be, for example, to compute the two image signals to a third image, for example, by means of a difference or quotient process.  
         [0034]     The advantage of using two cameras is that the slight differences between image with light reflection and image without light reflection can easily be brought out, so that reliable detection is possible.  
         [0035]     In order to simplify the mechanical construction, it is also possible to house both cameras/detectors in a common housing  50 , optionally with a common objective, the interior construction of which is designed in such a way, for example, by using beam splitters, prisms etc. or by the exact alignment of the two sensors relative to one another, that both image signals are received exactly from the same point or a spatial calculation or calibration in the evaluating unit  47  is easily possible.  
         [0036]     If the material is being conveyed by a conveyor belt or a needle roller, in which case the spatial arrangement of the individual fibres or fibre bundles relative to one another does not change, that is, the transport is merely linear, then both cameras  46  and  49 , as shown in  FIG. 10 , can scan the surface also at different points. The evaluation is then effected in the manner described for  FIG. 9 .  
         [0037]     The described arrangements shown in FIGS.  6  to  10  can basically be used with linearly or circularly polarised light. In instances of the arrangements shown in FIGS.  6  to  8  it is advantageous, however, to use circularly polarised light, because this enables independence from the effect of the rotated position of the plastics items  44  to be achieved.  
         [0038]     Although the foregoing invention has been described in detail by way of illustration and example for purposes of understanding, it will be obvious that changes and modifications may be practised within the scope of the appended claims.