EP0426893A1 - Method and device for sorting - Google Patents

Abstract

The invention relates to a method and a device for sorting material, in particular glass granules or glass containers. A piece of the sorting material is irradiated from one side by light, in particular by white light. It is detected on the opposite side where the light emerges. According to the result of the detection, a fraction of the sorting material is led off separately. It is provided that the light intensity emerging from a piece of sorting material is measured separately for the range of one wavelength, in particularly separately for the ranges of two wavelengths. If two intensities are measured, and their difference is very small, colourless glass is present. Particularly suitable wavelengths are 450 nm and 550 nm. If the difference in the intensities is measurable, coloured glass is present. If, in this case, the intensity can be measured at 450 nm, the glass is green. If, however, the intensity cannot be measured at 450 nm, brown glass is present. A suitable device for carrying out the method provides a light source (4) on an accelerating trough (3) for pieces of sorting material. Arranged opposite the light source (4) is a beam splitter (25) downstream of which are connected a detector (5) for 450 nm and a detector (6) for 550 nm. <IMAGE>

Description

The invention relates to a method for sorting items to be sorted, in particular glass granules or glass containers, wherein a piece of the items to be sorted is irradiated from one side with light, in particular with white light, it being detected on the opposite side whether light emerges, and wherein a fraction of the goods to be sorted is separated and discharged according to the result of the detection. The invention also relates to a device for performing this method.

A sorting system. which is suitable for sorting sorted goods according to their permeability to light of different colors is known from DE-OS 34 45 428. To sort glass, it is fed to a separating belt to which a colored glass sorting device is assigned. The sorting device has a light barrier that shines through glass pieces. The associated light source emits white light. The light barrier has several detectors. At least three detectors are available, which are sensitive to white, brown or green light. All detectors are connected to wipers via a downstream control, which sheds the supplied material classified according to color.

The known device provides for the sorting of glass for each type of glass, colorless, brown or green, a special light converter or detector.

Since all of the glasses present in the goods to be sorted represent a mixture in terms of their color, the glass color cannot be clearly determined with a short exposure. Even colorless glass contains green and brown parts. The green glass contains brown parts and the brown glass contains Green parts. In order to ensure the most reliable sorting possible with the known device, each piece of glass must be irradiated over a relatively long time. The light detected over this period is integrated. It is only this integral that can be used to determine with certainty which type of glass is present. However, the required integration process makes it necessary for the glass pieces to be passed between the light source and detectors as slowly as possible. This limits the throughput of the sorting device.

The invention was based on the object of specifying a method for sorting sorted goods, in particular glass granules or glass containers, which requires only a few detectors and can be operated at high throughput. Only two detectors should be necessary to sort the sorted goods into four components, opaque pieces of waste, colorless glass, brown glass and green glass. In addition, it should not be necessary to integrate the detected light for each piece of waste, so that a high throughput during sorting is ensured.

A facility for carrying out the method is also to be specified.

The first-mentioned object is achieved according to the invention in that the intensity of the light emerging from the item to be sorted is measured for the region of one wavelength, in particular separately for the regions of two wavelengths.

Whole wavelength sections, such as green, are therefore not registered in a detector, but only light of a specific wavelength, which can be specified in nanometers, or a narrow range around this wavelength is registered.

This has the advantage that, with a suitable selection of the wavelengths, a piece from the material to be sorted can be classified quickly and reliably with only one or with a maximum of two short measurements. Without complex integration of the received light, the method according to the invention can be used to determine whether a piece is an opaque material, colorless glass which is transparent to white light, brown glass or green glass. Since no integration has to be carried out, the advantage is achieved that reliable sorting with a high sorting speed is possible.

For example, in order to evaluate light intensity values measured for two wavelengths, their difference is first formed.

A fraction of the sorted goods is formed from those pieces of the sorted goods for which the difference is smaller and the two values are larger than predefined threshold values, which fraction is discharged separately. This fraction includes colorless glass.

With a few wavelength pairs for light intensity measurement, it is possible to mix up colorless and green glass. Therefore, these wavelength pairs are not to be used. This risk of confusion is due to the fact that the light intensity behind green glass fluctuates periodically in the range of visible light as a function of the wavelength. The light intensity behind colorless glass, however, is almost constant over the wavelength. Since an intensity difference below the threshold value is a criterion for colorless glass in the method according to the invention, the two wavelengths must be selected such that different intensities can be expected for green glass.

For example, light intensities are measured at a first wavelength below 500 nm and at a second wavelength above 500 nm. It then becomes, for example, a sorting fraction good pieces, in which the difference in light intensity values is greater and the light intensity value at the first wavelength is less than a threshold value. This fraction then only includes brown glass. This ensures that brown glass is reliably sorted out. This is due to the fact that brown glass almost does not transmit light with a wavelength below 500 nm, while light with a wavelength above 500 nm is transmitted.

For example, a fraction of items to be sorted is separated and removed in which the difference in the light intensity values and also the value of the light intensity at the first wavelength are greater than the threshold values. This fraction contains green glass.

With this procedure, colorless glass or brown glass or green glass can be reliably separated.

If there is no glass of a different color in the items to be sorted, as a colorless, brown and green glass, one fraction can be the remainder remaining after separation of two fractions.

For example, two light intensities are measured at a first wavelength of 450 nm and at a second wavelength of 550 nm. At 450 nm, the light intensity for green glass is a minimum, while for 550 nm it is significantly higher. For brown glass, the light intensity for 450 nm is almost zero, while for 550 nm there is a clear intensity.

For colorless and slightly dirty colorless glass, the light intensities for 450 nm and for 550 nm are almost the same.

With the selected two wavelengths for the light intensity measurement behind items to be sorted irradiated with white light, the method according to the invention achieves a certain degree of reliability casual and quick separation of a fraction from the sorted goods. This fraction can include either colorless or brown or green glass.

Sorting is also possible if the light intensity is only measured for one wavelength. Then the measured intensity value gives information about the type of glass.

For further sorting of the material to be sorted, it is irradiated with infrared light from one side, for example before or after irradiation with white light, and the intensity of the infrared light is measured on the opposite side. Another fraction is removed if the intensity is less than a threshold. This fraction then consists of all components that are not made of glass, such as. B. ceramics. The sorting goods that do not belong to this fraction and are not recognized as transparent (colorless), green or brown in the main sorting process then consist exclusively of glass of a different color or of glass that is either heavily soiled or has paper labels. This currently opaque glass can be cleaned for further sorting. It is also a good idea to mix the unsorted glass with the green glass, since a small addition of colorless and differently colored glass is harmless for further processing. With the additional sorting with infrared light, the advantage is achieved that the glass of different colors and the soiled or labeled glass can also be specifically fed for further processing, since it is separated from other material.

Metal parts can be removed from the goods to be sorted using suitable means, for example a magnet, even before the sorting described. The rest, which no longer contains glass, can also be sorted further.

For example, for the method according to the invention Sorted goods are irradiated with only one light source and the light that may have emerged from the sorted goods is divided and distributed to at least two detectors. On the one hand, this has the advantage that only one light source is required. On the other hand, there is a particular advantage in that fluctuations in the intensity of the emitted light can have no influence on the method. If two light sources were used, different and even opposite fluctuations in the emitted light intensities would be detrimental to the process.

To sort the items to be sorted, the detectors are connected to a control unit in which the intensity difference is also formed. A compressed air flow is controlled by this control unit, for example, which separates a certain fraction from the sorted material and conveys it to a certain container. The recognized pieces can also be separated in another suitable manner, for example with a controllable mechanical deflection device. Such a device is particularly suitable for glass containers. Several separating devices for different types of glass can also be arranged one behind the other.

A device for carrying out the method according to the invention has a conveying means for items to be sorted, on which a light source for illuminating the items to be sorted is arranged. At least one light detector is arranged opposite the light source and is connected to a sorting device via a control unit. The device for performing the method according to the invention is characterized in that each detector is sensitive to a certain wavelength of light.

This has the advantage that sorting with simple devices can be carried out quickly and reliably.

The sorting device comprises, for example, a compressed air valve which is arranged at the end of the conveying means and to which a container is assigned. After it has been recognized that a certain piece of the sorted material is to be assigned to the fraction to be separated, the compressed air valve is activated, whereby the piece falls into the container assigned to the fraction. The compressed air valve is e.g. B. connected to a compressed air tank or to a compressor. Any other sorting device can also be combined with the device for sorting according to the invention.

For example, only one light source is available for irradiating the sorted material and a beam splitter is arranged opposite the light source, the output beams of which are assigned to the detectors. This means that it is not necessary to compare different light sources.

The detectors are, for example, photodiodes, which can be preceded by interference filters. Good results are achieved with such an arrangement.

For further sorting, an infrared light source can be arranged on the conveyor in the conveying direction in front of or behind the light source, to which an opposite infrared detector is assigned. This detector is also connected to a sorting device via a control unit or evaluation unit. Through the further sorting, all items to be sorted apart from the glass pieces are separated. Thereafter, it can be assumed that the sorting material that is opaque to visible light consists of dirty glass pieces or pieces of glass stuck with paper labels. After separating the fraction that does not contain glass and colorless, brown and green glass, opaque glass and glass of a different color than brown or green currently remain.

With the method for sorting according to the invention and with the device for carrying out this method, the advantage achieved that with only a maximum of two detectors for visible light of certain wavelengths it is possible to separate a fraction from the sorted material, which can consist of colorless glass, brown glass or green glass. The sorting can take place at high speed since only one wavelength is measured at a time. The device for carrying out the method only requires a maximum of two detectors for optionally recognizing three types of glass.

Additional pre-sorting with infrared light can be used to separate non-glass items. After the later separation of colorless, brown and green glass, the only thing that remains is glass or glass of a different color, which is opaque due to dirt or labels. This glass can be mixed into the green glass without damage for further processing. All glass waste is therefore available for suitable further processing and reuse.

• FIG 1 zeigt eine Einrichtung zum Sortieren von Sortiergut;
• FIG 2 zeigt eine Lichtquelle und zwei Detektoren, die über einen Strahlenteiler in Verbindung stehen;
• FIG 3 zeigt die Lichtintensität hinter einem Glasstück als Transmission in Prozent für verschiedene Glassorten abhängig von der Lichtwellenlänge.

The method and the device according to the invention are explained in more detail with reference to the drawing:

• 1 shows a device for sorting sorted goods;
• 2 shows a light source and two detectors, which are connected via a beam splitter;
• 3 shows the light intensity behind a piece of glass as a transmission in percent for different types of glass depending on the light wavelength.

A device for sorting solid items according to FIG. 1 has a storage bunker 1, which is followed by a separating belt and an acceleration trough 3. The items to be sorted are located in the storage bunker 1. You reach the inclined acceleration channel 3 via the separation belt 2 and leave the pieces the separation band 2 individually and one after the other. To ensure this, the separating belt 2 is, for example, tapered and provided with a narrow outlet. There follows the acceleration trough 3, which is inclined to the horizontal. This speeds up the individual pieces. A light source 4 is arranged on the acceleration trough 3 and irradiates the individual pieces with white light. Detectors 5 and 6 are arranged on the acceleration channel 3 opposite the light source 4. These register the light intensities behind each piece that is irradiated by the light source 4. The first detector 5 measures the light intensity at the wavelength 450 nm. The second detector 6 measures the light intensity at the wavelength 550 nm. The two detectors 5 and 6 are connected to an evaluation unit 7, which can be a process computer. A compressed air valve 8 in a line 10 starting from compressed air tanks 9 is controlled by the evaluation unit 7. The line 10 ends at a compressed air nozzle 11. The outlet for the compressed air jet of the compressed air nozzle 11 is aligned with the end of the acceleration trough 3. When the compressed air valve 8 is open, the pieces brought in via the acceleration trough 3 are thrown into a first container 12 by the air flow. When the compressed air valve 2 is closed, the pieces enter a second container 13 which is arranged directly below the end of the acceleration channel 3. If the detectors 5 and 6 recognize components of a fraction of the material to be separated, for example colorless glass, brown glass or green glass, the compressed air valve 8 is opened and the components enter the first container 12. The rest reaches the second container 13.

With appropriate dimensions, the device according to FIG. 1 can also be used for sorting entire glass containers, for example bottles.

Instead of a separation with compressed air, a separation with as such known mechanical separation devices.

Openings in the containers 12 and 13 are downstream of conveyor belts 14 and 15. The first conveyor belt 14 for the separated fraction can lead to a glass melting furnace. The second conveyor belt 15 for the rest then leads to the separation of a further fraction to a storage or storage bunker 1 or directly to another sorting device for another type of glass.

For further sorting, the goods to be sorted can be fed to a similar, similar device in which the light source is an infrared light source 16. The detector is an infrared detector 17. Since the permeability to infrared light with glass, even if it is dirty or provided with paper labels, is greater than with other material, the material to be sorted can be separated into glass and other material by means of infrared light. The glass also includes the glass that is opaque to white light. Detection with infrared light can be connected downstream or upstream of detection with white light. The infrared detector 17 is connected to the evaluation unit 7, which is connected to a compressed air valve 18 in a line 19 extending from the compressed air tanks 9. The line 19 ends at a compressed air nozzle 20. The outlet for the compressed air jet of the compressed air nozzle 20 is directed towards the end of the upper part 3a of a two-part acceleration channel 3. If the infrared detector 17 does not respond, the compressed air valve 18 is open. The pieces which are brought up via the acceleration trough 3 and which are not made of glass are then thrown into an additional container or into a discharge line 21 by the air flow.

When the compressed air valve 18 is closed, the pieces, which consist of glass, flow onto the second part 3b of the acceleration channel 3, which is arranged downstream of the first part 3a.

If all sorting goods that are not made of glass have been sorted out with the infrared detector 17, the goods that cannot be separated out with the detectors 5 and 6 can be mixed into the green glass. This good then consists of dirty glass or glass that is neither colorless nor green or brown. Such glass does not interfere with the expected quantities in the production of green glass.

FIG. 2 shows the beam path from the light source 4 to the two detectors 5 and 6 in detail. Only one light source 4 is used so that the light intensity to be introduced into the sorting pieces is the same for both detectors 5 and 6. According to FIG. 2, the light source 4 is assigned a condenser lens 22 in front of the acceleration channel 3. A collecting lens 23 and an aperture 24 are located behind the acceleration trough 3. A beam splitter 25 is then arranged. From this beam splitter 25, a first partial beam goes to the first detector 5 via an interference filter 26 and a second partial beam goes to the second detector 6 via another interference filter 27.

The method carried out with the device according to FIGS. 1 and 2 is explained with FIG. The transmission, that is the light intensity behind a body as a percentage of the light intensity in front of the body, is dependent on the type of glass but also on the wavelength of the light for glass. For colored glass in particular, the transmission changes greatly depending on the wavelength of the light.

FIG. 3 shows the transmission τ as a function of the wavelength λ of the light for five different types of glass that can occur in the waste glass. The light wavelength in nm is plotted on the abscissa and the transmission in percent is plotted on the ordinate. The transmission for colorless, clean glass 28 is almost for all wavelengths of visible light constant between 80% and 100%. Even for colorless, lightly soiled glass 29 and for colorless, heavily soiled glass 30, the transmission hardly changes with the wavelength. Due to the degree of soiling, the transmission is for colorless; lightly soiled glass 29 approximately 50% and for colorless, heavily soiled glass 30 approximately 20%. Brown and green glass do not show a constant transmission curve at a changed wavelength. Brown glass 31 has no transmission at a wavelength below 500 nm, ie it is opaque for these wavelengths. Above 500 nm to approx. 600 nm wavelength, the transmission increases up to approximately 30% and drops slightly again at higher wavelengths. Green glass 32 shows a transmission curve that rises and falls several times with increasing wavelength. There is no transmission below 350 nm. In the 400 nm range, two consecutive maxima are reached at 60%. This is followed by a minimum at 450 nm and approximately 30% transmission. Then a maximum is reached again at approx. 530 nm and approx. 65%. This is followed by another minimum at 650 nm and approximately 30% transmission. As the wavelength increases, the transmission also increases. The transmissions shown for brown glass 31 and for green glass 32 each apply to clean glass. When dirty, the curves for brown glass 31 and for green glass 32 are shifted downwards on the ordinate, but retain their shape.

In order to obtain four fractions, opaque material, colorless glass, brown glass and green glass from the sorted material, two transmission measurements for two specific light wavelengths are sufficient according to the method of the invention. A first measurement at 450 nm light wavelength and a second measurement at 550 nm light wavelength are suitable. Small deviations don't hurt. The two measured transmission values and the difference between the two transmission values to be calculated are used to clearly identify the type of glass. All calculations and comparisons take place in the evaluation unit 7 according to FIG. 1.

Colorless glass that is transparent is recognized and can be separated if the transmission values are greater than a threshold value and the difference between the two transmission values is less than a threshold value. Then there is a piece in which there is a constant, measurable transmission for the two wavelengths under consideration. According to FIG. 3, this is the case for colorless glass, irrespective of whether it is clean, slightly soiled or heavily soiled.

If the difference between the transmission values for 450 nm and for 550 nm wavelength is greater than a threshold value, brown or green glass is present.

A distinction is made between colored glass and brown and green glass by looking at the transmission value at the wavelength of 450 nm. If the transmission there is below a threshold value and at the same time the difference between the transmission values is greater than a threshold value, brown glass is present. However, if the transmission at 450 nm is above a threshold value and at the same time the difference between the two transmission values at 450 nm and 550 nm is greater than a threshold value, green glass is present.

After the colorless, brown and green glass has been separated off, the fourth fraction is a residue which contains opaque material and can also contain glass of a color other than brown and green.

With the device shown, pieces of waste can be sorted quickly and reliably using simple means. It is noted that different types of glass, such as colorless, brown and green glass, have different transmission profiles depending on the wavelength of the incident light. The old household glass consists of colorless, brown and green glass, which is separated quickly and reliably using the method and the device according to the invention. This results in larger quantities of single-grade glass of higher quality than before and even more waste glass can be used in the manufacture of colorless and also brown glass. This is the only way to make new containers out of the old glass, which are either colorless brown or green.

As a result, less glass has to be made from raw materials, which leads to a saving in energy use.

With infrared light, material that is not glass can be sorted out of the material to be sorted. In the further sorting already described, after the colorless, brown and green glass has been separated off, a remnant remains which consists of glass of a different color and of glass which is opaque because it is heavily soiled or has labels attached to it. This small remainder can be added to the green waste glass. This does not falsify the green color.

The material to be sorted can be made of granules, e.g. B. from fragments, or from containers, for. B. consist of bottles.

Claims (15)

1. A method for sorting goods to be sorted, in particular glass granules or glass containers, wherein a piece of the goods to be sorted is irradiated from one side with light, in particular with white light, it being detected on the opposite side whether light emerges and with a fraction the sorted goods are separated and removed according to the result of the detection,
characterized in that the intensity of the light emerging from the item to be sorted is measured for the region of one wavelength, in particular separately for the regions of two wavelengths. 2. The method according to claim 1,
characterized in that the difference is formed from two measured intensities and that a fraction is separated in which the difference is smaller and the two intensities are greater than a respective threshold value (colorless glass). 3. The method according to any one of claims 1 or 2,
characterized in that a first light intensity is measured at a wavelength that is less than 500 nm and that a second light intensity is measured at a wavelength that is greater than 500 nm. 4. The method according to claim 3,
characterized in that the first light intensity is measured at 450 nm wavelength and the second light intensity at 550 nm wavelength. 5. The method according to any one of claims 2 to 4,
characterized in that a fraction is separated in which the difference is greater than a threshold value and the light intensity in a Wavelength less than 500 nm, especially at the wavelength 450 nm, is less than a threshold value (brown glass). 6. The method according to any one of claims 2 to 5,
characterized in that a fraction is separated in which the difference is greater than a threshold value and the light intensity at a wavelength less than 500 nm, in particular at the wavelength 450 nm, is greater than a threshold value (green glass). 7. Method according to one of claims 1 to 6,
characterized in that the material to be sorted is irradiated with infrared light from one side before or after the irradiation with white light, in that the intensity of emerging infrared light is detected on the opposite side, and in that a fraction is separated in which the infrared intensity is less than a threshold value is (ceramics, stones, etc.). 8. Method according to one of claims 1 to 7,
characterized in that the material to be sorted is irradiated with only one light source (4) for visible, in particular for white light, and in that light emerging from the material to be sorted is divided into at least two detectors (5, 6). 9. The method according to any one of claims 1 to 8,
characterized in that the fraction to be separated is conveyed with a stream of compressed air into a container (12) or into a discharge line (21). 10. Device for carrying out the method according to one of claims 1 to 9, wherein on a conveying means for sorted material, in particular on an acceleration trough (3), the sorted material is arranged to illuminate a light source (4), and at least opposite the light source (4) a detector (5, 6) arranged for light, which is connected to a sorting device via an evaluation unit (7),
characterized in that each detector (5, 6) is sensitive to a certain wavelength of light. 11. The device according to claim 10,
characterized in that only one light source (4) is present and in that a beam splitter (25) is arranged opposite the light source (4), the output beams of which are assigned to the detectors (5, 6). 12. Device according to one of claims 10 or 11,
characterized in that detectors (5, 6) are photodiodes. 13. Device according to one of claims 10 to 12,
characterized in that detectors (5, 6) are connected upstream of interference filters (26, 27). 14. Device according to one of claims 10 to 13,
characterized in that an infrared light source (16) is arranged on the conveying means, in particular on the acceleration channel (3) in the conveying direction in front of or behind the light source (4), to which an infrared detector (17) opposite it is assigned, which is connected to an assigned sorting device stands. 15. Device according to one of claims 10 to 14,
characterized in that the sorting device comprises a compressed air nozzle (11, 20) which is arranged at the end of the conveying means, in particular the acceleration trough (3) or the upper part (3a) of the acceleration trough (3) and which has a container (12) or a discharge line ( 21) is assigned.

Images