EP0734789B1 - Device and method for sorting bulk material - Google Patents

Abstract

Bulk materials are sorted into two fractions according to colour and/or shape. An arrangement of a conveyor for the material and opto-electronic scanners detect particles over the width of the material stream at the end of a chute (12). An electronic image processor forms a two-dimensional image of the stream from successive line signals from the scanners so that a particle can be recognised. Air blast nozzles (10) divert particles from a normal channel (32) to a separate channel (26) according to the evaluation of each particle. An air suction fan (28) is provided in the diversion channel t maintain uniform air conditions.

Description

The invention relates to a method and a device for sorting bulk goods in two fractions Color and / or shape according to the preamble of the main claim, corresponding to that known from EP-A-0 396 290 State of the art.

Methods and devices for sorting out have become more recent increasingly for sorting out certain stones Particle size or color from a bulk material flow for Sorting ergot from bulk grain, for Sorting out glass of different colors and for sorting out of impurities from glass, for sorting from plastic to color or transparency and to Sort food and pharmaceuticals by Color, e.g. B. with French fries and corn flakes, or by shape, e.g. B. in case of tablet breakage and according to minimum sizes, e.g. B. of fruit, related.

Another device of the generic type is known from EP 0 550 944 known in the non-transparent particles of transparent Particles are separated.

The device described there has the task set to sort particles of different sizes. The different trajectory is problematic here objects of different sizes. This is through a with grooves provided conveyor belt released. After the particles have separated from the conveyor belt, they go through a Flight route, being observed by a CCD camera whose signal to control blow-out nozzles, which correspond to the individual pixels of the CCD camera assigned, is used.

The problem here is that even when a first section of a larger particle Blow nozzle is triggered by the fact that it on the front edge of the particle blows this particle in an uncontrolled wobble that moves under Circumstances can cause the particle not to blown in a different direction as intended is, but only set in rotation.

Due to the lack of adaptation to large or small particles depending on the setting of the preselected one Time delay poor sorting characteristics for different sized particles. Next will be different heavy particles, for example sorting out of aluminum from glass, the bad adjustment to the different flight or fall curves and Speeds cause different levels of gravity Particles can be blown out poorly. Because the construction its geometry is fixed, it cannot be relegated calibrate different materials to be sorted out. Neither can, for example, by moving slower of the bulk material, an adaptation to another Bulk goods. Sorting by different Color characteristics are not possible.

Due to the longer drop distance in which the particles settle turn or stagger (at least not straight), it is with the device according to the cited document possible particles on the driven nozzles fall by. A user controlling the device does not have the ability to change by individual System parameters targeted to the current sorting characteristics act. To certain sorting characteristics to adapt to the bulk material, it must be lengthy Sorting tests with evaluation of the results achieved in each case carry out. This makes sorting by itself changing bulk material compositions practically impossible.

Finally, the device is from the cited document unable to bulk different Shapes or sizes according to these characteristics sort by.

Another document, EP 0 426 893, relates to one similar device in which by scanning at two Wavelengths are a color differentiation from green and brown glass should be made. A more universal Adaptation to other colors is not without further possible, and the image processing speed conceptually too slow to work efficiently to be able to.

So it is suggested there that only one light Use light source and beam splitter in front of a variety of photodiodes to use, in front of which then interference filters should be used. Control through however, the signals from the photodiodes will not continue executed.

The invention is therefore based on the object of a method or a method To create device with which a sorting of various Bulk goods is possible and improved Sorting with the least possible wrong sorting at high throughput. Give the subclaims further advantageous embodiments of the invention again, individually or in combination for special Purposes can be realized.

In particular, instead of one in the bulk material flow Backlit camera also uses cameras be working under reflected light, or there may be one Combination of two cameras facing each other are used, each under reflected or transmitted light conditions work. Preferred is one under incident light conditions working camera with two fluorescent tube elements on both sides of the observation beam path are arranged. This can be used for Most applications have achieved low-cost lighting become.

The use is particularly advantageous according to the invention a bulk chute attached to the trajectory of the free If approximated, but still slightly horizontal, so that all particles are still sliding on the bulk chute move, is to be provided, which serves a to produce a similar trajectory for all particles and further ensures that the particles between the time of observation and blowing out rotate and in their relative spatial relationship with the others neighboring particles remain the same as possible. This enables an aluminum chip, that flies differently on longer free fall routes than for example broken glass on the chute from the broken glass is taken away so that it is the same Speed reached.

Furthermore, the bulk material slide makes it possible to individual bulk particles on a conveyor belt to isolate a vibrating device. The vibrating device without bulk chute would leave upon leaving otherwise uneven output speeds produce. Through the bulk chute the output speeds have evened out.

In a further preferred embodiment, the advantageously easily replaceable bulk chute can also be provided with guide grooves with trapezoidal Cross section in the direction of the extension of the Bulk chute ensure that transverse movements of individual Bulk particles largely in straight motion is transferred. It is also advantageous that Bulk goods chute for different materials to produce different materials. Except for one Plastic version used in some applications due to electrostatic charges from a Bulk slide made of glass can also be replaced conceivable for food technology applications (e.g. Sort rice or cereals) a bulk chute made of metal with profiled guide grooves.

In particular, however, is electronic image processing advantageous according to the invention, the successive Line signals a two-dimensional, for a brief picture of the bulk material flow generated.

Two-dimensional images are usually in the Television technology by scanning a two-dimensional Image area reached. However, it is also possible to use one to scan one-dimensional line if that Bulk goods, as in the present case, moved on uniformly.

This two-dimensional image can be produced on a Screen are displayed, being particularly advantageous is when the ones to be blown out after image signal processing Particles are displayed in a different color. This allows the user to put him on the conveyor apparent sorting ratio with that of the device to visually compare the rejected sorting ratio. Furthermore, the correct detection of the objects clearly presented to the user at all times become. For example, objects should be essential other shape or number on the screen Image signal processing than actually for example Seeing on the conveyor is a parameter the device, e.g. B. readjust the speed. Of course, this readjustment can also be automatic according to the blow-out statistics recorded and the user to carry out this readjustment appropriate signals, for example to a control center or alarm signals are announced.

The use of a is particularly advantageous here recursive filter, which is to be sorted out with homogeneously distributed Bulk particles, for example ergot and rye grain, with changing sorting statistics notify the user in good time can.

If, for example, the color of the not to be sorted out Bulk, non-ergot, itself changed significantly, and now, for example Tripled the proportion of bulk material recognized as ergot, can sort out the rejection characteristics using the recursive filter be changed accordingly so that again only a selected part of the grain is sorted out becomes. Since this presupposes that the to be sorted out, for example the ergot, actually is homogeneously distributed, should suit the user Notification be made so that this is the case can control the acceptance again.

Due to the individual adaptability of the electronic Image signal processing on different particle sizes or conditions that the form must meet, it is possible to sort different bulk goods without a major hardware conversion is required. Through the Using color cameras is real time color viewing possible, being used by the electronic Image signal processing each captured object assigned a specific color by averaging or the like can be. If necessary, an object can also viewed from different directions through two cameras be so that, for example, when tablets break all possible positions of damaged tablets are recorded can be checked and checked in all these positions may be full or half tablets.

Likewise, the color is on both sides of an object can be checked independently of one another, so that if necessary both transmitted light and incident light information through combination in electronic image signal processing can be determined for a single object and this can be sorted accordingly.

Due to the possibility of the bulk material flow and the sorting statistics and even the latest image information forward about the objects to be sorted out, it is possible to control centers for under certain circumstances a plurality of these devices with image information both of the bulk material itself, for example by Viewing on the conveyor belt and detailed information about the quantity and type of the sorted out particles and possibly a second class of objects, the comes closest to the sorted out particles, as well as with an indication of when the sorting characteristics change to remove sorted particles.

This makes it considerably easier for the user to decide whether by changing certain sorting characteristics also sorting these out Class wishes.

Next is by using the bulk material slide achieved that flat particles along the Align extension of the chute and also in this direction their compared to the state of the art Technique start much shorter flight movement so that it the air outlet nozzles possible much more reliably is to pressurize them with air. An acceleration, for separating the bulk particles in the bulk material flow is desired, nevertheless takes place in at least the same degree instead. Due to the possibility of Object formation in a two-dimensional image can Centers of gravity of the particles are blown, so it can Avoid having a leading edge of the particle is pressurized with compressed air, which is an undesirable Wobble of the particle.

Fig. 1

eine Schnittdarstellung der erfindungsgemäßen Vorrichtung von der Seite, und

Fig. 2

ein Blockdiagramm für den Fall der Echtfarb-Echtzeit-Verarbeitung.

Further features and advantages of the invention arise from the following description of preferred exemplary embodiments of the invention. It shows:

Fig. 1

a sectional view of the device according to the invention from the side, and

Fig. 2

a block diagram in the case of real color real-time processing.

In Fig. 1 they are both in the lateral directions up and down in guides 22 movable like pivotable blow-out nozzles 10 by a compressed air control 24 are controlled, shown.

The guides 22, 36, etc., for adjusting the Angular and spatial relations of the individual parts to each other serve, are each laterally on the side walls of the Ball bearing guides arranged by machine.

A conveyor belt equipped with a vibrating device (not shown) is in the upper area from the right the bulk material comes onto the bulk material chute 12 convey on which it is sliding down to the desired one Speed is accelerated, the bulk flow "pulled apart" and thus the particles isolated become. With an essentially straight-line continuation of their flight movement they become, as by the solid line and the one particle indicated, fall. The arranged essentially vertically to this Blow-out nozzles 10 cause certain air to be blown out Bulk particles in a sorting bulk channel 26.

In this bulk material channel 26, in which the air for blowing out being blown in are steadier to form Air conditions, to avoid air eddy formation a suction fan 28 and on the blown side wall of the shaft 26 provided air intake nozzles 30 intended.

Between the chute for blown bulk and a shaft 32 for not blown out, proper A bulkhead 16 is provided in bulk material with a pivoting device 18 via a continuous straight rod or plate connection coupled is to the exact location of the top edge of the partition 16 desired to place. Below shafts 26 and 32 are interchangeable drawers to catch the sorted good shown in the figure. Of course can larger containers or more here Processing plants follow.

Except for the blow nozzles 10, which are dotted in the direction of the blow arrow shown, lighting means 14th provided that each consist of two parallel to Extension of the bulk material slide, i.e. perpendicular to the Fluorescent tubes parallel to the drawing exist between which there is a distance. By this distance, which is also a slit a radiation allowed from outside the device, the Line cameras used according to the invention the bulk material flow observe. Here it is both possible under On and transmitted light conditions with at least one Camera (not shown) on the right and / or top left from the part of the device shown in the drawing placed to watch. Bulk particles either on the transparent bulk chute or preferably due to the lower optical interference observed just behind the bulk chute. Short behind the bulk chute the particles still have in the same direction as on the slide, so in one plane and at the same speed. Various Bulk particle properties can Do not change the trajectory there yet. Close to that The gap between two fluorescent tubes is approx. One to two centimeters of white stripe is provided, the each opposite camera as well illuminated Background serves.

With reference numeral 34 is a device for pivoting the bulk chute 12 shown with reference numerals 36 the side guides to the Height adjustment of the bulk material slide. This is also also adjustable sideways, like this too for the blow-out nozzles through the guides 22 and for the Light elements 14 by provided in their attachment Guided tours are provided.

The two-dimensional generated with this device Image is displayed on a color monitor, in particular it is advantageous that an image to build his many lines a certain time, for example one half a second needed while the rest of the picture stands still. During this half a second, a captured Bulk particles are stationary on the screen be recognizable so that its scope, color and size as well the amount of such particles is easily read by the user can be. Only after the line scan camera is sufficient Lines in the same place, but with moving bulk material flow recorded to fill an entire image, the display is replaced by a new one Image replaced.

A user can use this for a comparatively long time Viewing time of a pixel can tell whether the summarizing object-indicating pixels to two-dimensional Image objects that should correspond to the bulk particles, is dealt with correctly by the electronics, or whether objects that are too large or too small are recognized. Possibly can be adjusted.

However, it is also particularly advantageous that this Representation also shows object inclusions in a different color can be. This is especially for applications beneficial in ore or rock for inclusions to be examined.

In addition to black and white information, color information can also be used for an object. Here you can also the color information on the front as well also the back by arithmetic means to one Total color information can be summarized that For example, sorting according to different types of waste glass Colors much easier.

By classifying the picture objects formed into a It is a plurality of gray value and / or color value classes possible statistics about the sorted out and possibly to refine rejectable quantities significantly. Further can, for example, display with another Color is given advance information on the screen what is sorted out when changing the parameters could be without lengthy attempts of the User needs to determine if he is changing certain parameters the desired sorting result reached. At the same time it can be checked whether the contents of the collection container 20 during operation matches the statistics of the particles to be blown out, or the blow-out geometry has to be adapted.

Since inclusions can also be recorded, it is possible to use the system also for bulk particles after a relation between own size and Sort out the size of an inclusion. This can be both sorting out those bulk particles, where the bulk goods parts with larger inclusions make processing worthwhile, as well as the reverse Case sorting out those bulk goods parts that have such large inclusions that post-processing or use does not appear to make sense.

By using recursive image processing filters, it is possible, based on homogeneously distributed image material assuming that this homogeneous distribution stops, whenever the sorting statistics changed, also the sorting characteristics accordingly to change, so that again the same proportion of missing material is sorted out.

This is changing, especially for base material Color, for example cereals, of interest where it can be assumed that the ergot always has one constant admixture factor, but the basic grain can vary greatly in color.

A color line sensor is used for color information acquisition, which has a FZKINT color line camera interface is suggested. As shown in FIG. 2 the incoming pixel data streams using a multi-stage pipeline processed. As input data serve the three color channels red, green and blue. You need to are available in digitized, 8-bit wide form, like some color line cameras or the FZKSAIM module used for simulation purposes. At the output of the processing stands for each pixel 8-bit wide color class information available on one line, which are fed to an SBIP / L module can. The desired color space coding of the individual Classes are created by the content of several lookup tables (LUT's) determined. The following will focus on the individual Processing levels of the pipeline were discussed in more detail.

The first step is a line delay (Color Divergence). Their function is narrow with the geometric conditions of the camera used linked and was therefore physically the color line camera interface assigned.

The FZKINT especially does justice to the fact that at some color line cameras the individual colors (red, Green and blue) are assigned to separate CCD sensors are. This creates significant problems in color identification of edges that are parallel to the CCD camera run because the individual sensors first successively receive the new color value. During the Transitional wrong color values are therefore read out. The problem can be solved, however, that the individual color channels depending on their spatial separation be delayed accordingly. requirement for this procedure is the constant speed of movement of objects that are also software controlled the corresponding delay time is coupled.

With the help of the color divergence value, a variable one Line offset for the individual color components program and thus movement-related color divergence eliminate. As the maximum line offset between two spatially adjacent color channels (red: green, green: blue) 8 lines can be set.

It should be noted that the blue channel has no delay is provided. The objects must always be the first red, then the green and finally the blue color line happen.

Leaves after passing through the corresponding line delay the pixel data stream reaches the FZKINT and reaches the CCD lookup tables on a color line preprocessing facility. There is then a separate LUT for each color channel available (rccd-LUT, gccd-LUT, bccd-LUT). she serves linearization and offset correction of the CCD sensor. It can also be used for white balance.

The incoming color data are converted from the RGB space into the YUV color space. Y corresponds to the intensity and U, V to the color components using the following formula: Y = 0.299 R + 0.587 G + 0.114 B U = B - Y V = R - Y.

In order to use the maximum data width of 8 bits, the sizes U and V are scaled so that they lie in the value range -127 to +127.
u = 0.5649 U
v = 0.7138 V.

The advantage of the YUV color space is that you get a "color" which is independent of brightness. Differences in thickness or differences in lighting will therefore not be Color differences do more.

After subsequent normalization and scaling based on Tables are programmed into the colors 8-bit value assigned, so that for example from a Only 16 million colors in the YUV area 1000 can be selected. Subsequently, several such Colors can be combined into a class.

As a result of uneven illumination, the brightness value Y fall off at the edge of the line. The transformation in the YUV color space carries this "shading" error Bill.

Just like in the black and white process, the Color process the use of a recursive filter possible. The recursive filter works just like that shading correction on the brightness signal. In contrast to the latter, which the brightness differences within compensate for one line, this works recursively Filters as brightness correction across several lines.

The color signals in the YUV space are also called chrominance referred to, which is advantageously independent of the Are luminance.

In Fig. 2 is finally within dashed lines The optional online statistics are shown, which are guided over the objects recorded in each case. The optional morphology processor is used for recursion.

With changing mechanical properties, for example, more moist grain, the angular relationships, especially the bulk material slide the exhaust nozzles and the relative position of these to each other along the intended guides and angle adjustment devices if necessary, be changed automatically. Suitable sensors for e.g. humidity, temperature or similar environmental factors if necessary be provided additionally.

Before making such adjustments to the angular relationships or recursive filters, the sorting characteristics greatly change, it can be provided that Alert the user of this beforehand.

Claims (11)

1. Method for sorting bulk material into at least two fractions on the basis of colour and/or shape with the steps of:

   conveying the bulk material particles in a bulk material flow of predetermined width,

   detecting the bulk material particles over the bulk material flow width using optoelectronic scanning means in the vicinity of the end of a chute,

   deflecting individual bulk material particles by the selective operation of blowout nozzles, which are provided along the width extension of the bulk material flow in a fall area, on the basis of the scanning results of the scanning means in a further, branched off bulk material flow,

   characterized by

   producing a two-dimensional image of a partial area of the bulk material flow from the successive line signals of the optoelectronic scanning means,

   detection of the objects in said image of the partial area of the bulk material flow,

   determining the gravity centres and use of the predetermined parameters on each object for which a plurality of scanning information exists,

   blowing out a bulk material particle by operating a nozzle at the time when it acts on the gravity centre of the particle to be blown out.
2. Method according to claim 1, characterized by the combination of object-displaying pixels to at least two-dimensional image objects, which correspond to the bulk material particles and in each case association of a grey and/or colour value information with each image object.
3. Method according to claim 2, characterized in that acquisition takes place with colour line cameras with spatially separated CCD sensors and part of the colour channels are individually delayed up to a line displacement of 8 lines in accordance with their spatial association.
4. Method according to claim 2 or 3, characterized by the conversion of the colour data from the RGB into the YUV colour space for compensating varying object thicknesses, edge shading and fluctuations in the illumination intensity.
5. Method according to one of the preceding claims, characterized by the classification of the image objects into one of a plurality of grey and/or colour value classes, display and/or logging of the objects to be blown out, together with the total number of objects detected and determination of a second classification class, which comes closest to the class of the objects to be blown out and the logging thereof for the optional elimination of also these objects.
6. Method according to one of the preceding claims, characterized by filtering with a recursive image signal processing filter for automatic adaptation to bulk material discolorations in the case of faulty material homogeneously distributed in the bulk material.
7. Method according to one of the preceding claims, characterized by a modification of the angle of the bulk material chute as a function of changes in the mechanical bulk material characteristics.
8. Apparatus for sorting bulk material using a method according to one of the preceding claims, characterized by an air suction device in the branched off bulk material channel for the blown out particles.
9. Apparatus according to one of the preceding claims, characterized by a moisture sensor.
10. Apparatus according to one of the preceding claims, characterized by a device for adjusting the bulk material chute angle.
11. Apparatus according to one of the preceding claims, characterized by a colour monitor for the display, fixed for half a second, of the object-displaying pixel of the detected two-dimensional image objects.

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