Patent Grant
7262380
1. Field of the Invention
This invention relates to determination in first and second dimensions of characteristics of material, for example automatic inspection and sorting of discrete objects of differing compositions, e.g. waste objects, or automatic inspection of sheet material, which may be in the form of a strip, for surface layer composition, e.g. surface layer thickness.
2. Description of the Related Art Including Information Disclosed under 37CFR 1.97 and 1.98
With the recent focus on collection and recycling of waste, the cost effectiveness of waste sorting has become an essential economic parameter.
In the “Dual System” in Germany all recyclable “non-biological” packaging waste excluding glass containers and newsprint is collected and sorted in more than 300 sorting plants.
Objects can be sorted on the basis of:
To make a positive identification by automatic means is very difficult. Physical shape is normally quite distorted, making any camera-based recognition very complex unless the printing pattern is made in a specially recognisable way, or the carton is equipped with a recognisable marker or tracer.
Several sorting systems exist today that can sort a number of different plastics bottles/objects from each other when they arrive sequentially (i.e. one-by-one). The detection is based on reflected infrared spectrum analysis. To separate the various polymers a quite elaborate variance analysis has to be performed and thus detection systems become expensive. The objects being fed sequentially pass beneath the infrared spectral detector whereby infrared is shone onto the objects and the relative intensities of selected wavelengths of the infrared radiation reflected are used to determine the particular plastics compound of the plastics passing beneath the detection head. Downstream of the detection head are a number of air jets which blow the individual plastics objects into respective bins depending upon the plastics which constitutes the majority of the object.
A similar system is disclosed in U.S. Pat. No. 5,134,291 in which, although the objects to be sorted can be made of any material, e.g. metals, paper, plastics or any combination thereof, it is critical that at least some of the objects be made predominantly from PET (polyethylene terephthalate) and PS (polystyrene) as well as predominantly from at least two of PVC (polyvinyl chloride), PE (polyethylene) and PP (polypropylene), for example objects including: an object made predominantly from PET, an object made predominantly from PS, an object made predominantly from PVC and an object made predominantly from PE. A source of NIR (Near Infra Red), preferably a tungsten lamp, radiates NIR onto a conveyor sequentially advancing the objects, which reflect the NIR into a detector in the form of a scanning grating NIR spectrometer or a diode array NIR spectrometer. The detector is connected to a digital computer connected to a series of solenoid valves controlling a row of air-actuated pushers arranged along the conveyor opposite a row of transverse conveyors. The diffuse reflectance of the irradiated objects in the NIR region is measured to identify the particular plastics of each object and the appropriate solenoid valve and thus pusher are operated to direct that object laterally from the conveyor onto the appropriate transverse conveyor. The computer can manipulate data in the form of discrete wavelength measurements and in the form of spectra. A measurement at one wavelength can be ratioed to a measurement at another wavelength. Preferably, however, the data is manipulated in the form of spectra and the spectra manipulated, by analogue signal processing and digital pattern recognition, to make the differences more apparent and the resulting identification more reliable.
DE-A-4312915 discloses the separation of plastics, particularly of plastics waste, into separate types, on the basis of the fact that some types of plastics have characteristic IR spectra. In the IR spectroscopic procedure, the intensity of diffusely reflected radiation from each sample is measured on a discrete number of NIR wavelengths simultaneously and the intensities measured are compared. Measurements are taken on wavelengths at which the respective types of plastics produce the minimum intensities of reflected radiation. If, for example, three different plastics are to be separated, each sample is measured on three-wavelengths simultaneously, whereby one type of plastics is identified in a first comparison of the intensity of the reflected radiation on the lowest wavelength with that of the second-lowest wavelength and the other two types of plastic are determined in a second comparison of the greater intensity on one wavelength in the first comparison with the intensity on the third wavelength. To measure the light on particular wavelengths, respective detectors can have narrow band pass filters for the respective requisite wavelengths, and respective constituent cables of a split optical fibre cable are allocated to the respective detectors, the cable entry lying in the beam path of a lens for detecting the light reflected from the sample. Alternatively, a light dispersing element, e.g. a prism or grid, is placed in the beam path after the lens and several detectors are arranged to detect the NIR of the requisite wavelengths. Sorting facilities are controlled by utilising the detection data obtained by the comparisons. As a further example, five differing plastics, namely PA (polyamide), PE, PS, PP and PETP, may be separated, utilising measurement points at five differing wavelengths between 1500 nm. and 1800 nm.
EP-A-557738 discloses an automatic sorting method with substance-specific separation of differing plastics components, particularly from domestic and industrial waste. In the method, light is radiated onto the plastics components, or the plastics components are heated to above room temperature, light emitted by the plastics components and/or light allowed through them (in an embodiment in which light transmitted through the components and through a belt conveying them is measured) is received on selected IR wavelengths, and the material of the respective plastics components is identified from differences in intensity (contrast) between the light emitted and/or absorbed, measured on at least two differing wavelengths. The light emitted or allowed through is received by a camera which reproduces it on a detector through a lens. A one-dimensional line detector is usable, although a two-dimensional matrix detector or a one-element detector with a scanning facility can be employed. In order that the camera may receive the light on selected IR wavelengths, interference filters may be mounted either in front of the light source or in front of the lens or the detector. In an example in which the material of the plastics components is identified from the differences in intensity of emitted light at two differing wavelengths, the wavelengths are chosen to produce maximum contrast. This means that one wavelength is selected so that maximum intensity of the emitted light is obtained at a specified viewing angle, whereas the other wavelength is selected so that minimum intensity is obtained at that viewing angle. Changing of wavelengths may be achieved by mounting the filters on a rotating disc, with the frequency of rotation being synchronised with the imaging frequency of the detector. Alternatively, an electrically triggered, turnable, optical filter may be employed. The electrical signals generated by the detector are fed to an electronic signal processor, digitised, and subsequently evaluated by image processing software. It is ensured that the plastics components are at approximately the same temperature at the time of imaging, as differences in contrast can also be caused by temperature differences. The belt should consist of a material which guarantees constant contrast on individual wavelengths.
There is also previously known a system in which infrared spectral detection is performed from below the objects, with the objects passing sequentially over a hole up through which the IR is directed. Again, the infrared reflected is used to sort the objects according to the various plastics within the respective objects.
U.S. Pat. No. 5,260,576 and EP-A-484,221 disclose a method and apparatus for distinguishing and separating material items having different levels of absorption of penetrating electromagnetic radiation by utilising a source of radiation for irradiating an irradiation zone extending transversely of a feed path over which the material items are fed or passed. The irradiation zone includes a plurality of transversely spaced radiation detectors for receiving the radiation beams from the radiation source. The material items pass through the irradiation zone between the radiation source and the detectors and the detectors measure one or more of the transmitted beams in each item passing through the irradiation zone to produce processing signals which are analyzed by signal analyzers to produce signals for actuating a separator device in order to discharge the irradiated items toward different locations depending upon the level of radiation absorption in each of the items. The disclosure states that mixtures containing metals, plastic, textiles, paper and/or other such waste materials can be separated since penetrating electromagnetic radiation typically passes through the items of different materials to differing degrees, examples given being the separation of aluminum beverage cans from mixtures containing such cans and plastic containers and the separation of chlorinated plastics from a municipal solid waste mixture. The source of penetrating radiation may be an X-ray source, a microwave source, a radioactive substance which emits gamma rays, or a source of UV energy, IR energy or visible light. One example of material items which are disclosed as having been successfully separated are recyclable plastic containers, such as polyester containers and polyvinyl chloride (PVC) containers, which were separated using X-rays.
In an eddy current system for ejecting metal from a stream of waste, the discharge end roller of a belt conveyor normally contains a strong alternating magnetic field generated by permanent magnets contained within and distributed along the roller and counter-rotating relative to the sense of rotation of the roller. This field ejects metallic objects to varying degrees depending upon the amount and the conductivity of the metal of the object. Since metallic objects in which the metal content is small, for example post-consumer packaging cartons of a laminate consisting of polymer-coated paperboard and aluminium foil, are only weakly affected by the magnetic field, such cartons, if in a greatly deformed condition, tend not to be separated-out by the eddy-current ejection system.
Another known system uses an electromagnetic field for eddy current detection through induction of eddy currents in the metal in metallic objects and the detection output is used to control an air jet ejection arrangement but this time the objects are caused to queue up one after another in single lines.
U.S. Pat. No. 4,718,559 discloses selective non-magnetic detection of non-ferrous metallic particles in a mixture of the same with ferrous metallic particles and non-metallic particles and non-metallic particles derived from homogenised and magnetically treated municipal or like waste by a plurality of electronic detectors and separation of a non-ferrous metallic concentrate from the mixture. In the process, the waste particles, agglomerates or vicinity of detector coils in association with an electronic activation system which activates a particle remover, preferably pneumatic. The remover may be made up of an air supply line which conducts air to an air valve and jet-type spray unit which causes most of the non-ferrous metallic particles to fall into or onto a non-metallic residue conveyor, which is separated from a metallic concentrate conveyor by a partition.
Various systems are known for automatic inspection of a continuous strip of sheet material. One system includes a mechanical scanner reciprocated across the width of the strip as the latter advances past the scanner. Light containing IR is shone onto a transverse section of the strip and the scanner includes a transducer which detects the reflected IR at a plurality of locations across the section and emits electrical signals representing, for instance, the polymer layer thickness of a polymer layer/paperboard layer laminate. This is employed in a laminating machine to control the thickness of polymer deposited onto the paperboard.
U.S. Pat. No. 4,718,558 and U.S. Pat. No. 4,057,146 incorporated therein by reference disclose apparatus for optically sorting small lightweight objects such as beans and/or grains on the basis of size and colour. The small objects pass through the apparatus in a plurality of separate streams, each stream being fed from its own hopper to its own control gate to its own vibrating try and thence, through its own vertically positioned channel, to arrive at its own analysis head. Each analysis head is in the form of an annulus with the central opening directly beneath the outlet end of the corresponding channel and the small objects in the corresponding stream fall down through its central opening one after another with vertical separation therebetween. Illumination is supplied by a plurality of illuminating lamps. For each analysis head, the light reflected from it particular stream is conveyed to a plurality of photodetectors of that head. The reflected light is conveyed to that plurality of photodetectors by a plurality of optical fibres of the analysis head. A solenoid-operated compressed air valve is opened when an object in the stream is to be rejected into a rejection hopper; otherwise, the valve remains closed and the objects fall directly into an acceptance hopper. It appears that analysis circuits for the respective streams are housed in a common control unit having a control panel which displays information and allows an operator to control the apparatus, including the setting of parameters.
U.S. Pat. No. 4,996,440 discloses a system for measuring one or a plurality of regions of an object to be able to determine one or a plurality of dimensions of the object. In one example, the system utilises a mirror arrangement for transmitting pulsed laser light so that the light impinges downwards upon the object and for receiving the upwardly reflected light. The system includes a laser, a rotating planar mirror and a concave frusto-conical mirror encircling the planar mirror, which serve for directing the light beam towards the object. The frusto-conical mirror, the planar mirror and a light receiver serve for receiving light beams which are reflected from the object. Electronic circuitry connected to the light receiver serves for calculating the travel time of the beam to and from the object, with a modulator causing the light beam to be modulated with a fixed frequency and the rotating planar mirror and the frusto-conical mirror causing the light beam to sweep across the object at a defined angle/defined angles relative to a fixed plane of reference during the entire sweeping operation.
U.S. Pat. No. 6,068,106 discloses a unit for conveying products and having a main conveying device in the form of a belt conveyor; two secondary conveying deices for feeding respective streams of products to the main conveying device via respective inputs; and a distributing device for so controlling the two streams that the products in a first of the two streams, on reaching an output of the main conveying device, are offset with respect to the products in a second of the two streams, so as to form a single succession of products through the output. The two inputs are separated by a vertical partition extending towards the location where the two streams are combined.
According to a first aspect of the present invention, there is provided a method of automatically inspecting matter for varying composition, comprising advancing a stream of said matter through a detection station, emitting a detection medium to be active at a transverse section of said stream at said detection station, wherein said medium is varied by variations in the composition of said matter at said transverse section, detecting the varied medium at detecting means and generating detection data in dependence upon the variations in said medium, characterised by receiving the varied medium over substantially the width of the stream at receiving means which physically extends across substantially the width of said stream and which transmits the varied medium towards said detecting means, and also characterized in that the varied medium converges upon itself during its travel from said receiving means to said detecting means.
According to a second aspect of the present invention, there is provided apparatus for automatically inspecting matter for varying composition, comprising advancing means for advancing a stream of said matter, a detection station through which said advancing means advances said stream, emitting means serving to emit a detection medium to be active at a transverse section of said stream at said station, detecting means serving to generate detection data in dependence upon the variations in said medium, and data-obtaining means connected to said detecting means and serving to obtain said detection data therefrom, characterised by receiving means at said station arranged to extend physically across substantially the width of said stream and serving to receive detection medium varied by variations in the composition of said matter at said section, and to transmit the varied medium to said detecting means such that the varied medium converges upon itself during its travel from said receiving means to said detecting means.
Owing to these aspects of the present invention, it is possible for the stream to be relatively wide, so that the inspection rate can be increased, and yet the capital cost of the detecting means need not increase in the same proportion.
The detection medium can be electromagnetic radiation, for example IR or visible light to detect variations in constituency or colour, or an electromagnetic field to detect metal portions of the stream, e.g. in sorting of materials. A wide variety of materials may be sorted from each other, but particularly plastics-surfaced objects sorted from other objects. For the present automatic sorting, the objects must be distributed in substantially a single layer.
Preferably, for sorting of objects, the objects are advanced through the detection station on an endless conveyor belt. If the objects to be separated-out are plastics objects which are substantially transparent to the electromagnetic radiation, e.g. IR, then the conveying surface of the belt should be diffusely reflective of the electromagnetic radiation.
For a polymer, two or more detection wavelength bands in the NIR region of 1.5 microns to 1.85 microns can be employed. For a laminate comprised of polyethylene on paperboard, a first wavelength band centred on substantially 1.73 microns is employed, as well as a second wavelength band centred less than 0.1 microns from the first band, for example at about 1.66 microns.
The matter may comprise laminate comprised of a first layer and a second layer underneath said first layer and of a material having a spectrum of reflected substantially invisible electromagnetic radiation significantly different from that of the material of the first layer. As a result, the spectrum of substantially invisible electromagnetic radiation, particularly IR, reflected from such laminate can be readily distinguishably different from the spectrum of the radiation reflected from a single layer of the material of either of its layers.
Using substantially invisible electromagnetic radiation, particularly IR, has the advantage of permitting more effective determination of the composition of the first layer.
In cases where the first layer is a polymer, e.g. polyethylene, for the diffusely reflected IR from the substrate to be sufficient for detection purposes, the first layer should be no more than 1 mm. thick. Its thickness is advantageously less than 100 microns, preferably less than 50 microns, e.g. 20 microns.
If the stream is a continuous strip of laminate advancing on a laminating machine, for example a polymer coating machine coating a polymer layer onto a substrate, it is possible to detect any variation in composition of the advancing polymer layer and to correct the coating process accordingly.
Alternatively, it is possible to separate-out objects, e.g. waste objects, of a predetermined composition from a stream of matter, e.g. waste matter, which can be relatively wide compared with a sequential stream, so that a relatively high rate of separation can be achieved.
According to a third aspect of the invention, there is provided a method of automatically inspecting matter for varying composition, comprising advancing a stream of said matter through a detection station, emitting a detection medium to be active at a transverse section of said stream at said detection station, wherein said medium is varied by variations in the composition of said matter at said transverse section, receiving the varied medium over substantially the width of the stream at receiving means which physically extends across substantially the width of said stream, and generating detection data in dependence upon the variations in said medium, characterised in that said transverse section comprises a multiplicity of individual detection zones distributed across substantially the width of said stream, and the detection data from said individual detection zones is used to construct a two-dimensional simulation of said matter passing through said detection station.
Typically, there could be a transverse row of some 25 to 50 detection points for a stream 1 m. wide. A central detection system can be applied to “serve” all 25 to 50 detection points if there is sufficient IR intensity across the width of the stream from a single or multiple IR source or even if there is an infrared source at each detection point. Optical fibres may lead the reflected IR from the detection points to this central detection system. However, a system of IR reflectors is preferred to optical fibres, since a reflector system is less expensive, allows operation at higher IR intensity levels (since it involves lower IR signal losses) and is less demanding of well-defined focal depths. If the stream moves at some 2.5 m/sec. and the system is capable of 100 to 160 scans across the stream each second, then detections can be made at a spacing of some 2.5 to 1.5 cm along the stream. When each scan is divided into 25 to 50 detection points, detections can be made in a grid of from 1.5×2.0 cm. to 2.5×4.0 cm. The transverse scanning of the moving stream makes it possible to construct a two-dimensional simulation which can be analyzed using image processing. In this way it is possible to detect:
The detection data processing system will determine wanted/unwanted composition at each point.
For thickness measurement of a surface polymer coating of a packaging web comprised of a paperboard substrate and the polymer coating on the substrate, the apparatus scans the moving web and measures the thickness of the polymer coating by monitoring two lines in the IR spectrum. The IR passes through the polymer and is partially absorbed on the way. When past the polymer layer it meets the paperboard substrate, which diffusely reflects the IR. The diffusely reflected IR travels back through the polymer and is again partially absorbed. The diffusely reflected IR leaving the polymer surface passes to a detector which reads the incoming IR. The absorption will be a measure of “absorption length”, viz. the thickness of the polymer layer. The two IR lines are chosen so that one is largely absorbed in the polymer and the other not, so functioning as a reference. Both IR lines are chosen to have low absorption in fibre.
The rough fibre surface largely gives diffuse reflection, while the polymer mainly gives direct reflection, which is not measured.
For food quality control, the apparatus measures the quality of foodstuff by monitoring the absorption spectrum in the IR range. Fat content and maturing of fish, and the maturing of meat is today measured by single detectors only capable of single point measurements. Only the low range of the IR spectrum (<1 micron) is currently used, restricting the available information. The present apparatus enables much wider analysis in the IR spectrum, and also enables an almost continuous total quality control.
In separating beverage cartons from a stream of waste, the signals from each of the wavelength bands are combined using signal processing for each detection. The two-dimensional simulation which is built up as the stream passes the detection station can be processed using robust statistical data analysis. For example, a logical rule may be applied where a minimum cluster of positive detections, for instance 3×3, is required before the system recognises a possible beverage carton. In high speed system (e.g., 2.5 m./sec. belt speed) only slight air pulses (an air cushion) are required to alter the carton exit trajectory from the belt sufficiently that they can land in a bin separate from other objects dropping freely. Normally, some 15-30 positive detections are made on a 1 liter carton. The peripheral detection points in the clusters can thus advantageously be disregarded, only initiating the air pulses according to the interior detection points, so securing more lift than tilt.
In slower speed systems (e.g., 0.2-0.5 m/sec belt speed) more positive air ejection pulses may be required to expel the cartons from the remaining stream. This requires air pulses hitting the cartons near their centres of gravity to avoid uncontrolled ejection trajectories.
Although an advantage of arranging the detection of objects from underneath (rather than above) the waste stream is that it gives as uniform a distance from detection point to object as possible, it has disadvantages which more than outweigh that advantage. By irradiating the waste objects on a conveyor belt with radiation from above and by utilising a reflector system to select that portion of the reflected radiation which propagates roughly vertically, the system can be made very focusing insensitive.
According to a fourth aspect of the present invention, there is provided apparatus for automatically inspecting matter for varying composition, comprising advancing means for advancing a stream of said matter, a detection station through which said advancing means advances said stream, emitting means serving to emit a detection medium to be active at a transverse section of said stream at said station, receiving means at said station arranged to extend physically across substantially the width of said stream serving to receive detection medium varied by variations in the composition of said matter at said section, detecting means serving to generate detection data in dependence upon the variations in said medium, and data-obtaining means connected to said detecting means and serving to obtain said detection data therefrom, characterised in that said station is a metal-detection station, said emitting means serves to emit an electromagnetic field, and said receiving means comprises a multiplicity of electromagnetic field sensing devices arranged to be distributed across said stream.
Owing to this aspect of the invention, particularly effective detection of metal is obtainable.
Thus, in addition to or instead of spectral sensing devices, electromagnetic sensing devices may be employed at a metal-detection station. By means of an antenna extending across the advancing means, an alternating electromagnetic field can be set up across the advancing means. By providing as many eddy current detection points (in the form of individual detection coils) across the advancing means as there are spectral detection points a simultaneous metal detection can be performed at very low additional cost.
Thereby, with a waste stream including polymer-coated beverage cartons, and with several air jet arrays arranged one after another it becomes possible to sort out:
With a more elaborate spectral analysis it also becomes possible to identify and sort out the type of polymer in a plastics object. The system could hence be applied to sorting into separate fractions the various plastics types occurring.
An important cost factor in the spectral analysis system, whether mirror systems or fibre optic systems are used, is the method chosen to “serve” the detection points.
According to a fifth aspect of the present invention, there is provided a method of automatically inspecting matter for varying composition, comprising advancing a stream of said matter through a detection station, irradiating with electromagnetic radiation comprising substantially invisible electromagnetic radiation a section of said stream at said station, scanning said section and determining the intensity of substantially invisible electromagnetic radiation of selected wavelength(s) reflected from portions of said stream, and obtaining detection data from said detection station, characterised in that said scanning is performed in respect of a plurality of discrete detection zones distributed across said stream and in that said determining is performed for each detection zone in respect of a plurality of said wavelengths simultaneously.
Owing to this aspect of the present invention, it is possible to increase the rate of reliable detection.
One device scanning all of the detection points should be the simplest and least expensive. A high-quality, high-speed device is required, but one optical separation unit with the required number of separation filters and detectors can then serve all detection points.
Frequency multiplexing IR pulses to all detection points is another alternative but this system would be more sensitive to interference and more costly than the first alternative.
Time multiplexing, whether of IR pulses to all detection points or of analysis of the diffusely reflected IR, can be somewhat simpler than frequency multiplexing, but implies that spectral identifications in the various wavelengths should be done sequentially, which could pose practical problems and limitations.
Determination that post-consumer beverage cartons contain polyethylene-coated paperboard can advantageously be done with only a few IR wavelengths analysed. Only NIR wavelengths seem to be required to be analysed, for example:
Wavelength no. 5, 2.028 microns, is quite moisture-sensitive and may advantageously be omitted. This will leave a very low number of wavelengths to be analysed and compared, thus increasing the maximum computational speed of the system considerably compared to existing systems designed for elaborate polymer absorption characteristic comparison.
According to a sixth aspect of the present invention, there is provided a method of separating polymer-coated paperboard objects from a stream of waste, comprising advancing said stream through a detection station and separating the polymer-coated paperboard objects from the stream, characterised in that at said station a determination is made, using substantially invisible electromagnetic radiation, solely as to whether a portion of said waste is or is not a polymer-coated paperboard object.
Owing to this aspect of the invention, it is possible to minimize the number of radiation wavelengths required to be analyzed.
Of the hereinbefore mentioned group of wavelengths Nos. 1 to 5, at least Nos. 2 and 3 are advantageously employed where IR radiation is utilized for separating-out of polyethylene-coated board, since, of common objects in a waste stream, paper and polymer-coated paperboard are the most difficult to distinguish between with IR detection and those two wavelengths give good discrimination between paper and polymer-coated paper.
According to a seventh aspect of the present invention, there is provided a method of automatically inspecting matter for varying composition, comprising advancing through a detection station a first stream of matter, emitting detection medium to be active at a transverse section of said stream at said detection station, wherein said medium is varied by variations in the composition of said matter at said transverse section, obtaining from said detection station first detection data as to a constituent of said first stream, characterised by advancing a second stream of matter through said detection station simultaneously with said first stream, emitting detection medium to be active at a transverse section of said second stream at said detection station, wherein the latter medium is varied by variations in the composition of matter of said second stream at the latter transverse section, and obtaining from said detection station second detection data as to a constituent of said second stream, and also characterised in that the varied medium from both of the first and second streams is received by a receiving device common to both streams.
According to an eighth aspect of the present invention, there is provided apparatus for automatically inspecting matter for varying composition, comprising a detection station, first advancing means serving to advance through said station a first stream of matter, first emitting means serving to emit detection medium to be active at a transverse section of said stream at said detection station, a receiving device serving to receive detection medium varied by variations in the composition of said matter at said section, detecting means serving to produce first detection data as to a constituent of said first stream at said station, characterised in that second advancing means serves to advance a second stream of matter through said station simultaneously with said first stream, and second emitting means serves to emit detection medium to be active at a transverse section of said second stream at said detection station, in that said receiving device serves also to receive detection medium varied by variations in the composition of the matter at the latter section and is thus common to both of the first and second advancing means, and in that said detecting means serves to produce second detection data as to a constituent of said second stream.
Owing to these aspects of the invention, whereby one-and-the-same detection station is employed for at least two streams simultaneously, the capital and running costs of inspection can be reduced compared with a case where the streams have respective detection stations.
The first and second streams can pass through the detection station in respective opposite directions or in a common direction. In the latter case, the streams can be conveyed on an upper run of an endless belt, with a partition along the upper run to keep the streams apart. The streams can be inspected for respective constituents of differing compositions or of the same composition, in which latter case the second stream can be a separated-out fraction of the first stream, to produce a final separated-out fraction of increased homogeneity.
In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:
Referring to
In an alternative form of scanner, the 24 optical fibres terminate at a single fixed disc, mounted opposite to which is a rotating disc carrying 6 (or 12) IR filters passing six wavelengths. Beyond the rotating disc is a ring of 24 detectors. The rotating disc is opaque to IR and the IR passes through that disc only at the locations of the filters. However, since all 6 filters must pass the terminal of one of the optical fibres before a small carton can pass the corresponding detection point, the opaque disc must rotate at a very high speed, at something like 30,000 rpm. Moreover 24 detectors are required compared to the above-mentioned 6.
In an alternative embodiment, a single source of IR illuminates a chopper wheel which effectively emits six streams of IR radiation of a pulsed form, each stream being of a different pulse frequency. These IR streams are then fed by optical fibres to the detection points and the reflections at those detection points are then electrically detected and fed to a single electric processor. However, a disadvantage of this embodiment is that the conversion of the IR into pulsed IR means that the light intensity at the detection points is relatively much reduced and as a consequence the focal depth is relatively critical. It also requires a relatively very fast digital processing system to separate all of the frequencies and produce control outputs where required.
Referring to
An IR transmission system 107, 108 is based on metallic mirrors. By using a reflector 107 in the form of roughly a conical segment, with roughly a vertical cone axis, it is possible to select that portion of the reflected IR from the objects on the conveyor belt which propagates in roughly a vertical direction, thereby making the system very focusing insensitive. This is because, if the only IR which is detected is roughly vertical, then variations in the heights of objects does not produce false readings caused by hiding of short objects by tall ones or by misrepresentation of the actual positions of objects. Height variations of the objects of up to 20 cm can be tolerated, provided that the objects are sufficiently well irradiated.
By using a reflector 107 in the form of a doubly-curved surface of the shape of part of a torus an extra focussing effect of the IR reflected from a given detection point towards an optical separation/detection unit 120 can be obtained. This will allow more of the reflected IR from a given detection point to be focussed onto the unit 120 than that which propagates in a strictly vertical direction. Thereby, a significant intensity increase can be obtained compared to use of planar or conical reflectors.
By using a rotating polygonal (in this case hexagonal) mirror 108 in front of the optical separation/detection unit 120, it becomes possible to scan an almost arbitrarily chosen number of detection points per scan. The arbitrary choice is possible because the unit 120 is adjustable to sample at chosen, regular intervals. Six times per revolution of the mirror 108, a scan of the width of the conveyor belt is made. With the reflector 107, the “scan line” 121 on the conveyor belt is a circular arc. With a differently shaped reflector, the scan line can be straight. For example, instead of the reflector 107 of roughly conical segment form, it is possible to use a series of individual planar or doubly-curved mirrors appropriately angled to converge the IR towards the mirror 108. This reduces the data processing capacity required compared with the version shown in the Figure, because the distances from the detection points to the air jets 116 at the end of the belt 104 are then equal to each other. Using a hexagonal mirror reduces the necessary rotational speed of the mirror to one-third of a “front and back” 2-mirror configuration. The reflector system 107,108 has low losses and it is possible to operate at high intensity and signal levels. This makes the material/object identification less susceptible to noise in the form of, for instance, stray light and internally generated noise in the opto-electronic systems.
As shown in
By applying a beam splitter and optical filter combination for each wavelength to be analysed, all selected wavelengths can be analysed simultaneously referring to the same spot on the object surface.
As an alternative to the beam splitter and filter combination 122 and 113, “negative” optical filters in the form of selectively reflecting surfaces can be employed. Such a negative filter mounted at an oblique angle will transmit nearly all light outside a particular wavelength, and the latter would be reflected to the appropriate detector. All detectors can then operate at much higher signal levels than when a beam splitter and “positive” filters are used.
In slowly operating sorting installations, it is conceivable that the IR wavelengths can be scanned sequentially, so that there is no need to split the reflected IR beam. An error source will occur in that the various wavelengths are not referred to exactly the same spot, but this may be acceptable when the conveyor belt is moving at low speed. By chopping the reflected IR 25 to 50 times per scan by utilising the motion of the polygonal mirror 108, a series of filters can be scanned for each detection location, and by an internal reflector in the optical detection unit all signals can be led to the same detector. This can also be achieved by having the filters mounted in a rotating wheel in front of the detector. The advantage of these solutions is that all detections are made with the same detector, avoiding sensitivity and response differences developing over time in a set of several detectors. Cost savings may also be realised.
The air jet ejection system for the selected waste objects may be a solenoid-operated nozzle array, indicated as 116 in
In high-speed conveying systems, the belt 104 may have a speed in excess of 2 m/sec. The objects will then have a sufficient speed in leaving the belt at the end that only a weak air impulse, which might even be an air cushion, is required to change the trajectory. Possibly all detection points can be made to trigger such a weak air impulse allowing a very simple logic for the nozzle control, because there would be no need to calculate the centre of gravity of the object.
The analogue signals from the detector 120 are fed to an analogue-to-digital converter and data processor 135 the output from which is supplied to a controller 136 for solenoid valves (not shown) which control the supply of compressed air to the respective nozzles of the array 116.
Instead of or in addition to the IR-detection arrangement 105, 107, 108, 120, there may be employed, at the same detection station 131 or a second detection station 131, a metal-detection arrangement also illustrated in
Referring to
Referring to
The two lanes 161 and 166 or the two conveyors 104A and 104B could advance respective streams from which respective differing types of material (for example laminated material and purely plastics material, or, as another example, laminated material and wood-fibre material or metallic material) are to be separated-out. In that case, the conveyor 164 would be omitted, the hopper 162 would discharge into a bin a stream fraction comprised of the material separated-out into the hopper 162 and the remainder of the stream advanced by the lane 161 or conveyor 104A would be forwarded by the conveyor 163A to the slide 165 to constitute the stream on the lane 166 or conveyor 104B, and the hopper 167 would discharge into a bin a second stream fraction comprised of the other material to be separated-out.
The various embodiments utilising detection by radiation and described with reference to
Referring to
Advantages of this version are that it separates waste into three fractions in a single-stage operation and that an IR detection system can be fitted to an already installed eddy current ejection system, without any need to alter either system significantly.
Referring to
| Number | Date | Country | Kind |
|---|---|---|---|
| 9416787.1 | Aug 1994 | GB | national |
| 9503472.4 | Feb 1995 | GB | national |
This Application is a Divisional of our U.S. patent application Ser. No. 08/776,689 filed as International Patent Application Serial No. PCT/1B95/00672 on Aug. 2, 1995 and issued on 9 May 2000 as U.S. Pat. No. 6,060,677.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4718558 | Castaneda | Jan 1988 | A |
| 4909930 | Cole | Mar 1990 | A |
| 5555984 | Sommer, Jr. et al. | Sep 1996 | A |
| 6060677 | Ulrichsen et al. | May 2000 | A |
| 6068106 | Brizzi et al. | May 2000 | A |
| Number | Date | Country |
|---|---|---|
| 484221 | May 1992 | EP |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 08776689 | US | |
| Child | 09541718 | US |
