Abstract:
The invention relates to a device and method for separating bulk materials with the aid of a blow-out device provided with blow-out nozzles arranged on a fall section which is disposed downstream from a conveyor belt. The blow-out nozzles are controllable by computer-controlled evaluation means according to sensor results of radiation, which penetrates the flow of bulk material on the conveyor belt, and emitted from an x-ray source and captured in the sensor means. The x-ray radiation, which passes through the particles of the bulk material, is filtered into at least two spectra of differing energy ranges before the radiation is captured by local resolution with the aid of at least one sensor means integrated within an energy range.

Description:
PRIOR APPLICATIONS  
       [0001]     This application is a U.S. continuation-in-part basing priority on international application S.N. PCT/DE2004/002615, filed on Nov. 25, 2004, which in turn bases priority on German application S.N. 10 2004 001 790.5, filed on Jan. 12, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates to a device and a method for separating or sorting bulk materials according to the preamble of the main claim.  
         [0004]     2. Description of the Prior Art  
         [0005]     Devices for separating bulk materials require a large number of sensors, particularly optical and electromagnetic sensors, such as is described in the applicant&#39;s EP B1-1 253 981.  
         [0006]     Besides such sensors it is also advantageous to use X-radiation for the non-destructive testing of material characteristics of all possible objects, which are not readily detectable on the surface.  
         [0007]     In this connection, U.S. Pat. No. 6,122,343 only provides the information given in the introductory part of claim  1 , and only the reference that superimposed arrays can be used as sensor means indicate the possible appearance of the filters on the detectors. No further details are given of data processing and, instead, merely an increased contrast image constitutes the sought result.  
         [0008]     Particularly, through the observation of a high resolution image while observing two X-radiation energy levels and the mathematical evaluation of a resulting differential image, makes it possible to obtain information on the constituents of individual bulk material particles, but no teaching in this direction is provided by U.S. Pat. No. 6,122,343.  
         [0009]     This is, for instance, of interest when separating ores, where the decision as to whether a particle is or is not discarded decisively depends on whether and possibly which material is present in a specific bulk material particle. The method can also be used in the separation of waste particles.  
         [0010]     In known devices where X-ray sources were used, as a result of the not inconsiderable spatial dimensions of the X-ray sources and also the detectors, as well as the necessary screening or shielding, spatial demands have arisen making it impossible or only possible with considerable difficulty to bring about a place-precise evaluation, such as is required for the control of blow-out nozzles for blowing out smaller bulk material particles.  
         [0011]     The problem of the invention is to provide a safe-saving arrangement with which it is not only reliably possible to detect small metal parts such as screws and nuts, but permitting the reliable separation thereof from the remaining bulk material flow through blow-out nozzles directly following the observation location.  
       SUMMARY OF THE INVENTION  
       [0012]     According to the invention, this problem is solved by the features of the main claim and, using two X-ray filters for different energy levels which are, in each case, brought in front of the sensors, different information concerning the bulk material particles can be obtained. Alternatively, the filters can directly follow the X-ray source, or use can be made of X-ray sources with different emitted energies.  
         [0013]     The spatial arrangement of the filters can be fixed so that by moving the bulk material particles, it is possible to bring about a suitable filter-following reflection of the x-radiation, e.g., by crystals onto a detector line or row, in the case, of an association of two measured results recorded at different times for the bulk material particles advancing on the bulk material conveyor belt.  
         [0014]     However, in another variant of the device, it is also possible to work with two sensors, which follow one another transversely to the conveyor belt extension and are, e.g., located below the same. Through suitable mathematical delay loops, it is then possible to associate the successively obtained image information with individual bulk material particles and, following mathematical evaluation, use the same for controlling the blow-out nozzles.  
         [0015]     Through the upstream placing of filters, it is also possible to restrict the X-radiation to a specific energy level with respect to an X-ray source emitting in a broader spectrum prior to the same striking the bulk material particle. No further filter is then required between the bulk material particles and a downstream sensor.  
         [0016]     It is also proposed that the device be equipped with a shield which is, obviously, provided around the X-ray source and the irradiation location of the bulk material particles, and the actual sensors in a X-ray-tight manner, but which also extends on the bulk material conveyor belt surface up to a filling device filling the conveyor belt via a sloping chute. This ensures that operating personnel can remain around the sorting and separating device. Covers must be secured in such a way that on removal the device cannot be operated.  
         [0017]     The inventive method for separating bulk materials with the aid of a blow-out device operates with blow-out nozzles located on a fall section downstream of a conveyor belt, the blow-out nozzles being controlled by a computer-assisted evaluating means as a function of the sensor results of radiation penetrating the bulk material flow on the conveyor belt, which is emitted by an X-ray source and is captured in sensor means.  
         [0018]     Filtering of the X-radiation, which has traversed bulk material particles, takes place in at least two different spectra for the place-resolved capturing of the X-radiation, which has traversed the bulk material particles integrated in at least one line sensor over a predetermined energy range. This can take place when using a sensor means (a long line formed from numerous individual detectors) by passing through different filters and successive capturing of the transmitted radiation or, preferably, by two sensor lines with, in each case, a different filter, the filters permitting the passage of different spectra, which on the one hand tend to have a soft and on the other a hard character.  
         [0019]     A Z-classification and standardization of image areas takes place for determining the atomic density class on the basis of the sensor signals of the X-ray photons of different energy spectra captured in the at least two sensor lines.  
         [0020]     Finally, the objective can advantageously be achieved by a segmentation of the characteristic class formation for controlling the blow-out nozzles on the basis of both the detected average transmission of the bulk material particles in the different X-ray energy spectra captured by the at least two sensor lines, and also the density information obtained by Z-standardization. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The detailed description of the invention, contained herein below, may be better understood when accompanied by a brief description of the drawings, wherein:  
         [0022]      FIG. 1  illustrates a cut-away side view of  FIG. 2  of the device for separating bulk materials of the present invention;  
         [0023]      FIG. 2  illustrates a perspective view of the device of the present invention, shown with removed radiation protection above the conveyor belt;  
         [0024]      FIG. 3  illustrates a diagrammatic view of the method of the X-ray sensor means structure of the present invention;  
         [0025]      FIG. 3A  illustrates a diagrammatic view of the two-channel sensor means of  FIG. 3  of the present invention;  
         [0026]      FIG. 4  illustrates a diagrammatic view of the method of the X-ray signal processing structure of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIG. 1  shows a flat detector  10  positioned below a conveyor belt  20  and an X-ray source  12  positioned above a conveyor belt  20 , which by means of downstream blow-out nozzles  24  located in two different product chambers, it is possible to separate a rejection product from a pass-through product in the bulk material flow. A wedge-like separating element  26  between the two product flows can have its slope adjusted so that it is easily possible to adapt to products of different heaviness with different flight characteristics without the blow-out air pressure having to be subsequently adjusted.  
         [0028]      FIG. 1  also shows how, above the conveyor belt  20 , there is a cover  16  for preventing X-radiation reflected against the product delivery direction passing out to the separating device. On the filling side there is a seal  17  of the conveyor belt box  19  through a sloping material delivery chute  18  on conveyor belt  20 , so that radiation cannot pass out counter to the conveying direction parallel to the conveyor belt.  
         [0029]     The device for separating bulk materials with the aid of a blow-out device with blow-out nozzles  24  located on a fall section downstream of a conveyor belt  20  consequently largely comprises computer-assisted evaluating means which can be controlled as a function of sensor results of two captured X-ray transmitted light images penetrating the bulk material flow on the conveyor belt  20 , emitted by an X-ray source  12  and captured in sensor means  10 . There are also two filter devices (not shown) for passing on X-radiation in relation to mutually different energies placed upstream of the at least one sensor means  10 , said sensor means being line sensors with a plurality of individual pixels positioned transversely to the conveyor belt  20 . In particular, there can be one sensor line for each filter.  
         [0030]     A sensor line (not shown) corresponding to the conveyor belt width is formed by lined u4p photodiode arrays, whose active surface is covered with a fluorescent paper. The filters are preferably metal foils through which X-radiation of different energy levels is transmitted. However, the filters can also be formed by crystals, which reflect X-radiation to mutually differing energy levels, particularly X-radiation in different energy ranges in different solid angles.  
         [0031]     There can also be more than two filters for the use of more than two energy levels. Advantageously, the filters are located below the conveyor belt  20  upstream of the sensor means  10 , and above the conveyor belt  20  is located an X-ray tube  12  producing a brems spectrum.  
         [0032]     The device is equipped with a shielding box  14 , above the conveyor belt  20 , and surrounds the conveyor belt and the blow-out section  22 , whereby a cover  16  covers the conveyor belt  20  in a section upstream of the X-ray source  12 , and at the beginning of the belt there is a sloping chute  18  covering the entrance cross-section (shown respectively in  FIG. 2 ). In the device shown inter alias, glass ceramic is separated from bottle glass. However, the different glass types, as used in display screen tubes which in part have much higher melting points than “normal glass” and constitute a material difficult to separate in the recycling of broken glass, can now for the first time be separated using the device according to the present invention.  
         [0033]     For the better understanding of the separating procedure, a technical description will now be given of X-ray signal processing by means of two X-ray transmission spectra and segmentation into characteristic classes. A suitable coverage is to be ensured within the framework of X-ray sensor means (see  FIG. 3 ), and this is achieved by a filter technique having spectral resolution.  
         [0034]     Through a suitable filtering of the X-radiation upstream of the particular sensor of the two-channel system, there is firstly a spectral selectivity. The arrangement of the sensor lines then permits an independent filtering so that the optimum selectivity for a given separating function can be achieved.  
         [0035]     Generally, a higher energy spectrum and a lower energy spectrum are covered. For the higher energy spectrum, a high pass filter is used which greatly attenuates the lower frequencies with lower energy content. The high frequencies are transmitted with limited attenuation. For this purpose, it is possible to use a metal foil of a metal with a higher density class, such as a 0.45 mm thick copper foil. For the lower energy spectrum, the filter is used upstream of the given sensor as an absorption filter which suppresses a specific higher energy wave range. It is designed in such a way that the absorption is in close proximity to the higher density elements. For this purpose, it is possible to use a metal foil of a lower density class metal, such as a 0.45 mm thick aluminum foil.  
         [0036]     Each of the two sensor lines S 1 .i and S 2 .i (e.g., from n times 1 to n times 64 for all the lined up arrays over the conveying width) comprises a plurality of photodiode arrays equipped with a scintillator for converting X-radiation into visible light.  
         [0037]     A typical array has 64 pixels (in one row) with either 0.4 or 0.8 mm pixel raster. As diagrammatically shown in  FIG. 3 , by means of analog amplifiers and analog/digital converters  32 , the intensity is digitized with 14 bit dynamics and read out in line-synchronous manner using FIFO (First In/First Out) memories  34  and a serial interface  36 . The line first cut from the sorting product, as a result of the material conveying direction, is delayed until the data are quasi-simultaneously available with those of the subsequently cut line (with the other energy spectrum).  
         [0038]     The thus time-correlated data are converted by multiplexer  38  into a byte-serial data stream and transmitted via the standard interface Camera Link  40  over a distance of several meters to the evaluation electronics.  
         [0039]     By lining up electronic modules, which in each case cover a 300 mm conveying width, it is possible to build up in two-channel form maximum conveying widths of 1800 mm. For this purpose, on each module the necessary operating voltages are generated anew and the clock signals are prepared anew.  
         [0040]     The X-ray signal processing takes place on the data stream transmitted via Camera Link  40  (shown diagrammatically in  FIG. 4 ) and undergoes separation into two sensor channels, again using de-multiplexer  42 .  
         [0041]     For each channel, separately a black/white correction is carried out in an electronic unit  44 . On measuring this correction stage, for each pixel determination takes place of the black value in the absence of radiation and the white value for 100% radiation, and an adjustment or compensation table is used. In normal operation the untreated data are corrected with the aid of said table. For suppressing signal noise  46 , separately and for each channel by the buffer storage of a number of following lines, temporarily an image is built up and is smoothed by a mean value filter whose size in rows and columns can be adjusted. This significantly reduces noise.  
         [0042]     Z-transformation  50  produces from the intensities of two channels of different spectral imaging n classes of average atomic density (abbreviated to Z), whose association is largely independent of the X-ray transmission and, therefore, the material thickness.  
         [0043]     A standardization of the values to an average atomic density of one or more selected representative materials makes it possible to differently classify image areas on either side of the standard curve. A calibration, in which over the captured spectrum the context is produced in non-linear manner, enables the “fading out” of equipment effects.  
         [0044]     The atomic density class generated during the standardization to a specific Z (atomic number of an element or, more generally, average atomic density of the material) forms the typical density of the participating materials. In parallel to this, a further channel is calculated providing the resulting average transmission over the entire spectrum  48 .  
         [0045]     By computer-assisted combination of the atomic density class with a transmission interval (Tmin-, Tmax) to the pixels, can be allocated a characteristic class  52  which, following morphological filter  54 , can be used for material differentiation  56 .  
         [0046]     Here again in temporary manner, an image of a few lines height is built up in order to suppress interfering information with a bi-dimensional filter. It is, e.g., possible for undesired misinformation to be suppressed at the edge of particles by cut pixels.  
         [0047]     The data stream of characteristic classes  52  is treated as image material. The “machine idling” characteristic class describes the state when the X-ray source is switched on without sorting material in the measurement section. All characteristic pixels diverging from machine idling are processed as foreground and combined by segmentation to line segments, and finally to surfaces. The characteristic distributions over these surfaces are described by object data sets. In addition, said data sets also contain information regarding the position, shape and size of the linked characteristic surfaces.  
         [0048]     In the evaluation quantity relations of the characteristic pixels, as well as the shape and size per object, are compared with learned parameters per material. On this basis the object is associated with a specific material class.