EP0734789A2 - 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 device and a method for sorting bulk material in two fractions by color and / or shape according to the preamble of the main claim.

Devices for sorting out have recently become increasingly used for sorting out certain stones according to particle size or color from a bulk material flow, for sorting out ergot from bulk grain material, for sorting out glass of different colors and for sorting out impurities from glass, for sorting plastic by color or transparency and Sorting food and pharmaceuticals by color, e.g. B. for French fries and corn flakes, or by shape, e.g. B. at tablet breakage, and according to minimum sizes, eg. B. of fruit, related.

A generic device is known from EP 0 550 944, in which non-transparent particles are separated from transparent particles.

The device described there has set itself the task of sorting particles of different sizes. The problem here is the different trajectory of objects of different sizes. This is solved by a conveyor belt with grooves. After the particles have separated from the conveyor belt, they pass through a flight path, where they are observed by a CCD camera, the signal of which is used to control blow-out nozzles that are assigned to the individual pixels of the CCD camera.

The problem here is that when a first section of a larger particle is detected, a blow-out nozzle is triggered which, by blowing onto the front edge of the particle, sets this particle in an uncontrolled wobble movement, which under certain circumstances can cause the particle to be level not blown out in another direction as intended, but only rotated.

The lack of adaptation to large or small particles results in a poor sorting characteristic for particles of different sizes, depending on the setting of the preselected time delay. For particles of different weights, for example the sorting out of aluminum from glass, there is also poor adaptation of the different flight or fall curves and speeds cause particles of different weights to be blown out poorly. Since the structure is fixed in its geometry, it cannot be calibrated to different materials to be sorted out. It is also not possible to adapt to other bulk material, for example by moving the bulk material more slowly. Sorting according to different color characteristics is not possible.

Due to the longer fall distance in which the particles rotate or tumble (at least not straight), it is possible in the device according to the cited document that particles fall past the actuated nozzles. A user controlling the device does not have the option of specifically influencing the current sorting characteristic by changing individual system parameters. In order to adapt certain sorting characteristics to the bulk material, he has to carry out lengthy sorting tests with evaluation of the results achieved in each case. This makes sorting changing bulk material compositions practically impossible.

Finally, the device from the cited document is not able to sort bulk goods of different shapes or sizes according to these characteristics.

Another document, EP 0 426 893, relates to a similar device, in which a color distinction between green and brown glass is to be made by scanning at two wavelengths. However, a universal adaptation to other colors is not easily possible, and the image processing speed is conceptually too slow to be able to work efficiently.

So it is proposed to use the light from only one light source and to use beam splitters in front of a large number of photodiodes, in front of which interference filters are then to be used. However, the control by the signals from the photodiodes is no longer carried out.

The invention is therefore based on the object of providing a device which is capable of sorting a wide variety of bulk goods and which provides improved sorting with the least possible incorrect sorting at a high pressure set. The subclaims represent further advantageous embodiments of the invention, which can be implemented individually or in combination for special purposes.

In particular, instead of a camera which is viewed under backlighting in the bulk material flow, cameras can also be used which work under incident light, or a combination of two cameras directed in opposite directions can be used, each of which operates under incident or transmitted light conditions. A camera operating under incident light conditions is preferred, in which two fluorescent tube elements are arranged on both sides of the observation beam path. This enables lighting that is favorable for most applications to be achieved.

According to the invention, it is particularly advantageous to use a bulk chute that approximates the trajectory of free fall, but is still slightly horizontal, so that all particles still slide on the bulk chute move, is to be provided, which serves to create a similar trajectory for all particles and further ensures that the particles do not rotate between the time of observation and the blowing and remain in their relative positional relationship with the other neighboring particles as possible. This enables an aluminum chip that flies differently on longer free-fall distances than, for example, broken glass, to be carried along by the broken glass on the chute, so that it reaches the same speed.

Furthermore, the bulk material chute makes it possible to separate the individual bulk material particles on a conveyor belt by means of an oscillating device. The vibrating device without bulk chute would otherwise produce uneven exit speeds when leaving the conveyor belt. The exit speeds have become more even due to the bulk material slide.

In a further preferred embodiment, the advantageously easily replaceable bulk material chute can also be provided with guide grooves which, with a trapezoidal cross section in the direction of the extent of the bulk material chute, ensure that transverse movements of individual bulk material particles are largely converted into straight travel. It is also advantageous to manufacture the bulk material slide for different materials from different materials. In addition to a plastic version, which in some applications can be replaced by a bulk material slide made of glass due to electrostatic charges, a bulk material slide is also conceivable for food technology applications (e.g. sorting rice or grain) made of metal with profiled guide grooves.

In particular, however, the electronic image processing according to the invention is advantageous, which generates a two-dimensional image of the bulk material flow, which stands for a brief moment, from successive line signals.

Two-dimensional images are usually achieved in television technology by scanning a two-dimensional image area. However, it is also possible to scan a one-dimensional line if the bulk material continues to move uniformly, as in the present case.

This generated two-dimensional image can be displayed on a screen, it being particularly advantageous if the particles to be blown out are displayed in a different color after image signal processing. This enables the user to visually compare the sorting ratio visible to him on the conveyor belt with the sorting ratio recognized by the device. Furthermore, the correct detection of the objects can be clearly presented to the user at any time. If, for example, objects appear in a significantly different form or number on the screen after image signal processing than can actually be seen, for example, on the conveyor belt, one parameter of the device, e.g. B. readjust the speed. Of course, this readjustment can also take place automatically based on the recorded blow-out statistics and the user can be notified of this readjustment by appropriate signals, for example to a control center or alarm signals.

The advantage here is in particular the use of a recursive filter which, in the case of homogeneously distributed bulk material particles to be sorted out, for example ergot and rye grain, can inform the user in good time of changing sorting statistics.

If, for example, the color of the bulk material that is not to be sorted out, the non-ergot grain, changes significantly and, for example, the proportion of bulk material recognized as ergot has now tripled, the recursive filter can change the sorting characteristics accordingly, so that again only a preselected component of the Grain is sorted out. Since this presupposes that the material to be sorted out, for example the ergot, is actually homogeneously distributed, the user should be informed accordingly so that he can check the existence of the acceptance again.

Due to the individual adaptability of the electronic image signal processing to different particle sizes or conditions that the shape has to meet, it is possible to sort a wide variety of bulk materials without the need for major hardware modifications. The use of color cameras enables real-time color viewing, with the electronic image signal processing used being able to assign a specific color tone to each detected object by averaging or the like. If necessary, an object can also be viewed from different directions by two cameras, so that, for example, all possible positions of damaged tablets are recorded in the event of a tablet break can be and in all these positions can be checked whether whole or only half tablets are available.

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

The possibility of forwarding the bulk material flow and the sorting statistics and even the current image information about the objects to be sorted out makes it possible to control centers for a plurality of these devices with image information of both the bulk material itself, for example by viewing on the conveyor belt and detailed information about the To provide the quantity and type of the sorted out particles and possibly a second object class that comes closest to the sorted out particles, as well as an indication of the sorted out particles when the sorting characteristics change.

This makes it considerably easier for the user to decide whether he also wants this further class to be sorted out by changing certain sorting characteristics.

Furthermore, the use of the bulk material chute ensures that flat particles align themselves along the extent of the chute and that their flight movement, which is considerably shorter than that of the prior art mentioned, also begins in this direction, so that the air outlet nozzles are much more reliably capable of flushing them with air to act upon. An acceleration, which is desired for separating the bulk material particles in the bulk material flow, nevertheless takes place to at least the same extent. Due to the possibility of object formation in a two-dimensional image, the center of gravity of the particles can be blown on, so that it can be avoided that compressed air is applied to a front edge of the particle, which would result in an undesired wobbling movement 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.

1 shows the blow-out nozzles 10 which can be moved and swiveled in guides 22 both in the lateral directions upwards and downwards and which are controlled by a compressed air control 24.

The guides 22, 36, etc., which are used to adjust the angular and spatial relationships of the individual parts to one another, are each ball-bearing guides arranged laterally on the side walls of the machine.

A conveyor belt (not shown) provided with a vibrating device will convey the bulk material coming from the right to the bulk material chute 12, on which it will slide down to the desired speed, whereby the bulk material flow "pulled apart" and thus the particles are separated. Continuing their flight movement essentially in a straight line, they will fall, as indicated by the solid line and the one particle. The blow-out nozzles 10 arranged essentially vertically to this effect blow out certain bulk material particles into a sorting-out bulk material channel 26.

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

A partition 16 is provided between the shaft for blown-out bulk material and a shaft 32 for non-blown-out, proper bulk material, which is coupled to a pivoting device 18 via a continuous straight rod or plate connection in order to place the upper edge of the partition wall 16 exactly as desired. Interchangeable drawers for collecting the sorted goods are shown below the shafts 26 and 32 in the figure. Of course, larger containers or other processing systems can follow here.

In addition to the blow-out nozzles 10, which blow in the direction of the arrow shown in dotted lines, lighting means 14 are provided, each consisting of two fluorescent tubes running parallel to the extension of the bulk material slide, that is to say perpendicular to the plane of the drawing, between which a distance remains. This distance, which also allows a radiation from outside the device as a gap, the Line cameras used according to the invention observe the bulk material flow. It is possible to observe under reflected and transmitted light conditions with at least one camera (not shown) placed on the right and / or top left of the part of the device shown in the drawing. Bulk particles are observed either on the transparent bulk chute or, preferably due to the lower optical disturbances, just behind the bulk chute. Shortly behind the bulk material slide, the particles continue to fly in the same direction as on the slide, i.e. in one plane and at the same speed. Different bulk particle properties cannot change the trajectory there yet. Close to the gap between two fluorescent tubes there is an approximately one to two centimeter white stripe that serves as a well-lit background for the camera opposite.

With reference numeral 34, a device for pivoting the bulk material chute 12 is shown, with reference number 36, the laterally attached guides for height adjustment of the bulk material chute. This is also adjustable in the lateral direction, as is also provided for the blow-out nozzles by the guides 22 and for the lighting elements 14 by guides provided in their attachment.

The two-dimensional image generated with this device is displayed on a color monitor, it being particularly advantageous that an image takes a certain time, for example half a second, to build up its many lines, while the rest of the image is stationary. During this half a second, a detected bulk particle is stationary on the screen be recognizable so that its size, color and size, and the amount of such particles can be easily read by the user. Only after the line camera has recorded enough lines at the same location, but with a moving bulk material flow, to fill an entire image, is the display on the screen replaced with a new image.

Through this comparatively long viewing time of a pixel, a user can recognize whether the combination of object-indicating pixels into two-dimensional image objects, which are supposed to correspond to the bulk material particles, is handled correctly by the electronics, or whether objects that are too large or too small are recognized. If necessary, readjustments can be made.

However, it is also particularly advantageous that this representation can also be used to display object inclusions in a different color. This is particularly advantageous for applications in which ore or rock is to be examined for inclusions.

In addition to black and white information, color information about an object can also be acquired. In this case, the color information on both the front and the back can be combined by arithmetic means to form a total color information, which, for example in the case of waste glass, makes sorting by different colors considerably easier.

By classifying the image objects formed into a plurality of grayscale and / or color value classes, it is possible to significantly refine statistics on the sorted out and possibly sorted out quantities. Further, for example, representation with another Color information is given on the screen in advance, which could be sorted out if the parameters were changed without the user having to make lengthy attempts to determine whether he achieved the desired sorting result by changing certain parameters. At the same time, it can be checked whether the contents of the collecting containers 20 match the statistics of the particles to be blown out during operation, or whether the blow-out geometry has to be adapted.

Since inclusions can also be detected, it is also possible to use the system to sort bulk particles according to a relationship between their own size and the size of an inclusion. This can be both a sorting out of those bulk material particles in which the bulk material parts with larger inclusions make processing worthwhile, and in the opposite case a sorting out of those bulk material 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 to change the sorting characteristics of homogeneously distributed image material based on the assumption that this homogeneous distribution continues, whenever the sorting statistics change, so that the same proportion of missing material is again sorted out.

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

A color line sensor, which is provided with a color line camera interface FZKINT, is proposed for color information acquisition. As shown in FIG. 2, the incoming pixel data streams are processed using a multi-stage pipeline. The three color channels red, green and blue serve as input data. They must be available in digitized, 8-bit wide form, such as that supplied by some color line cameras or the FZKSAIM module used for simulation purposes. At the output of the processing, 8 bit wide color class information is available for each pixel of a line, which can be supplied to an SBIP / L module. The desired color space coding of the individual classes is determined by the content of several lookup tables (LUTs). The individual processing stages of the pipeline are discussed in more detail below.

In a first step, a line delay (color divergence) is carried out. Their function is closely linked to the geometric conditions of the camera used and was therefore physically assigned to the color line camera interface.

The FZKINT especially does justice to the fact that with some color line cameras, the individual colors (red, green and blue) are assigned to spatially separate CCD sensors. This results in considerable problems with the color identification of edges that run parallel to the CCD camera, since the individual sensors only get the new color value one after the other. Wrong color values are therefore read out during the transition. The problem can, however, be remedied by delaying the individual color channels depending on their spatial separation. A constant movement speed is a prerequisite for this procedure of the objects, which is also software-controlled and coupled to the corresponding delay time.

With the help of the color divergence value, a variable line offset for the individual color components can be programmed and thus color divergence due to movement can be eliminated. 8 lines can be set as the maximum line offset between two spatially adjacent color channels (red: green, green: blue).

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

After passing through the corresponding line delay, the pixel data stream leaves the FZKINT and arrives at the CCD lookup tables on a color line preprocessing device. A separate LUT is then available for each color channel (rccd-LUT, gccd-LUT, bccd-LUT). It is used for 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: $$\begin{array}{c}\begin{array}{c}\text{Y = 0.299 R + 0.587 G + 0.114 B}\\ \text{U = B - Y}\\ \text{V = R - Y.}\end{array}\end{array}$$

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. $$\begin{array}{c}\begin{array}{c}\text{u = 0.5649 U}\\ \text{v = 0.7138 V.}\end{array}\end{array}$$

The advantage of the YUV color space is that you get a "color" that is independent of brightness. Differences in thickness or differences in lighting will therefore no longer cause color differences.

After subsequent standardization and scaling using permanently programmed tables, the colors are assigned an 8-bit value, so that, for example, only 1000, for example, are selected from a set of 16 million colors in the YUV space. Then several such colors can be combined into one class.

As a result of uneven illumination, the brightness value Y can drop in the edges of the line. The conversion into the YUV color space takes this "shading" error into account.

As in the black and white processes, the use of a recursive filter is also possible in the color process. Like the shading correction, the recursive filter acts on the brightness signal. In contrast to the latter, which compensate for the differences in brightness within one line, the recursive filter acts as a brightness correction over several lines.

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

Finally, FIG. 2 shows the optional online statistics within dashed boxes, which are carried out over the objects detected in each case. The optional morphology processor is used for recursion.

In the event of changing mechanical properties, for example more moist grain, the angular relationships, in particular the bulk material chute but also the blow-out nozzles, and the relative position of these relative to one another along the provided guides and angle adjustment devices can be changed automatically, if necessary. Suitable sensors for, for example, humidity, temperature or similar environmental factors can optionally also be provided.

Before such adjustments of the angular relationships are carried out or recursive filters which change the rejection characteristics significantly, it can be provided that alarm means inform the user of this beforehand.

Claims (10)

Device for sorting bulk goods in at least two fractions by color and / or shape with: bulk material conveying means which move the bulk material particles in a bulk material flow of a predetermined width, - Optoelectronic scanning means which detect the bulk material particles across the width of the bulk material flow, and Blow-out nozzles which deflect individual bulk material particles into a further, branched-off bulk material flow along the width of the bulk material flow in a drop area by selective actuation on the basis of the scanning results of the scanning means, marked by a bulk material slide in the region of the end of which bulk material particles are detected by the optoelectronic scanning means, and electronic image processing means, which generate a two-dimensional image of the bulk material flow from the successive line signals of the optoelectronic scanning means, for detecting the objects and applying the predetermined parameters to each object for which a large amount of scanning information is available. Apparatus according to claim 1, characterized in that the scanning information filtered with methods of image signal processing is used to display and / or actuate associated nozzles at a point in time at which they act on the center of gravity of the particle to be inflated. Apparatus according to claim 1 or 2, characterized in that the bulk material chute is a guide chute for the bulk material, which essentially corresponds to the direction of flight of the particles in free fall. Apparatus according to claim 3, characterized by straight guide grooves which are profiled on the bulk material chute and run in the direction of the desired fall direction. Device according to one of the preceding claims, characterized by an air suction device in the branched pouring channel for the blown out particles. Device according to one of the preceding claims, characterized by a device for adjusting the angle of the bulk material chute. Method for sorting bulk material in two fractions by color and / or shape with a device according to one of the preceding claims, characterized by - Combining object-displaying pixels into at least two-dimensional image objects that correspond to the bulk material particles and assigning gray value information to the image objects of the two-dimensional image. Method according to one of the preceding method claims, characterized by Classification of the image objects formed into one of a plurality of gray value and / or color value classes, - Display and / or logging of the objects classified as blow-out in addition to the total number of objects detected, - Determination of a second classification class that comes closest to the class of the objects to be blown out, and their logging for optional sorting out of such objects as well. Method according to one of the preceding method claims, characterized by - Use of a recursive image signal processing filter in the case of homogeneously distributed defective material in the bulk material for automatic adaptation to bulk material discoloration. Method according to one of the preceding method claims, characterized by - Change in the mechanical angular relationships, in particular of the bulk material chute, as a function of changes in the mechanical bulk material characteristics.

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