GB2486797A

GB2486797A - Detecting plastic foreign bodies in fibre material

Info

Publication number: GB2486797A
Application number: GB1121735.3A
Authority: GB
Inventors: Engels Guido
Original assignee: Truetzschler GmbH and Co KG
Current assignee: Truetzschler GmbH and Co KG
Priority date: 2010-12-22
Filing date: 2011-12-16
Publication date: 2012-06-27
Also published as: ITMI20112032A1; BRPI1105736B1; CN102534875A; DE102010055523A1; CN102534875B; CH704296B1; GB201121735D0; CH704296A2; BRPI1105736A2; BRPI1105736B8

Abstract

A device in spinning room preparation for detecting foreign bodies 5 made of plastics, such as polyÂpropylene tapes in or between fibre tufts, packaging materials and waste plastics, causes fibre material 4 to be illuminated with non-polarised light of one wavelength range 8 and at the same time illuminated with polarised light of a different wavelength range 11 in such a way that both kinds of light can be used together in a machine at closely adjacent inspection stations 2, 12. Cameras 6, 15, 16 observe light reflected from the fibre stream in the inspection channel 1. The wavelengths may be visible light and infrared light and the device is provided with polarisation filters 13, 17.

Description

Device in spinning room preparation for detecting foreign bodies made of plastics The invention relates to a device in spinning room preparation for detecting foreign bodies made of plastics, such as polypropylene tapes, fabrics and films and the like, in or between fibre tufts, for example of cotton.

A problem that arises during operation of optically operating foreign fibre or foreign body separators in spinning room preparation machines for cotton or synthetic fibres is that they are unable to detect, or can detect only inadeguately, light-coloured, colourless or trans-parent plastics (such as, for example, packaging films or packaging fabrics made of polyethylene or polypropylene) on account of the low degree of optical contrast.

DE 10 2008 031 199 A (corresponding to GB2461371A) discloses the use of polarised light (transmitted light) in combination with simultaneous irradiation with UV light (reflected light) DE 103 47 240 A has already described a method in which, with the aid of polarised incident light, the surface gloss of the foreign bodies is determined and evaluated for detection. It has been found, disadvantage-ously, that such an arrangement cannot be combined with classic colour detection or with the method using polarised transmitted light in one inspection station, on account of their influencing one another. The provision of a further inspection station in a machine is also subject to limitations, because it is necessary to maintain minimum distances between the individual inspection stations in order to exclude mutual interference and the machines would become too large or the distances between the detection and separation stations become too large, so that the bodies cannot be separated or too much good material is separated at the same time.

It is an aim of the invention to improve the known devices. In particular, it is an aim of the invention to make it possible also to detect in fibre materials those packaging materials and waste plastics which are not detectable using polarised light (non-transparent) or detectable using UV light (non-fluorescent) The present invention provides a device in spinning room preparation for detecting foreign bodies made of plastics in or between tufts of fibre material, comprising illumination means for illuminating the fibre tufts and the foreign bodies with non-polarised light of one wavelength range and with polarised light of a different wavelongth range in such a way that both kinds of light can be used together in a machine at closely adjacent positions.

By illuminating the fibre material on the one hand with non-polarised light of one wavelength range and at the same time with polarised light of a different wavelength range in such a way that both kinds of light can be used together in one machine at closely adjacent inspection stations, it is made possible inter aiLs also to detect in fibre materials those packaging materials and waste plastics which are detectable neither using polarised transmitted light (non-transparent) nor using UV light (non-fluorescent) Advantageously, said closely adjacent positions comprise first and second inspection stations, each permitting illumination of the fibre tufts.

Advantageously, the first inspection station is arranged to serve for illuminating the tufts with the non-polarised light and the second inspection station is arranged to serve for illuminating the tufts with the polarised light.

Preferably, but not necessarily, the first inspection station is upstream of the second inspection station in the direction of travel of the fibre material.

Advantageously, the two inspection stations are identical.

Advantageously, the illumination means comprises a source of non-polarised light of one wavelength range and a source of polarised light of a different wavelength range.

Advantageously, the illumination means comprises a source of non-polarised light of one wavelength range and a source of polarised light of a different wavelength range arranged in a common housing. Advantageously, the necessary detector devices for the non-polarised light of the one wavelength range are arranged in a housing together with the sensors for the polarised light of the other wavelength range.

Advantageously, for the non-polarised light, wavelengths from the visible part of the spectrum are used. Advantageously, for the polarised light, wavelengths from the infrared part of the spectrum are used.

Preferably, for the non-polarised light, wavelengths from the visible part of the spectrum are used and, for the polarised light, wavelengths from the infrared part of the spectrum are used. Advantageously, to cover a large working width a plurality of detection devices operate in sections in parallel one next to the other.

Advantageously, to reduce the overall space required the camera lines of sight are bendable by mirrors or prisms.

The invention also provides the use of the devices according to the invention, together with a device which operates with polarised transmitted light and/or UV light in a machine in order to maximise the reliability of detecting colourless foreign bodies.

Advantageously, in the device of the invention fibre tufts are distinguishable from foreign bodies by an evaluation unit. For example, the evaluation unit may distinguish foreign bodies made of plastics such as polypropylene tapes, fabrics and films or the like from the fibre tufts, for example tufts of cotton. The evaluation unit may, especially, be arranged to detect plastics foreign bodies even where the degree of optical contrast with the surrounding fibre tufts is low, for example, where the plastics materials are light-coloured, colourless or transparent.

The invention also provides a device in spinning room preparation for detecting foreign bodies made of plastics, such as polypropylene tapes, fabrics and films and the like, in or between fibre tufts, for example of cotton, wherein the fibre material (fibre tufts) and the foreign bodies are illuminated on the one hand with non-polarised light of one wavelength range and at the same time with polarised light of a different wavelength range in such a way that both kinds of light can be used together in a machine at closely adjacent inspection stations.

Moreover the invention provides a method for detecting foreign bodies of plastics materials from a stream of fibre material comprising iiluminating the fibre material with non-polarised light of one wavelength and at the same or a closely adjacent location illuminating the fibre material at the same time with polarised light of a different wavelength. The invention also provides for the separation of foreign bodies detected using the device of the invention, for example by means of ejection of the foreign bodies from the fibre material using a blast of air.

Certain embodiments of the invention are explained in greater detail below with reference to the accompanying drawings, in which: Fig. 1 shows an embodiment of the device according to the invention in which all detection methods are used in a device or in a machine; Fig. 2 shows an arrangement similar to Fig. 1 in which both sensors of the cameras are housed in one camera housing; Fig. 3 shows an embodiment with a combination of the channels of the colour camera with the two infrared channels of the polarisation camera in one housing; Fig. 4 shows an arrangement in which the camera lines of sight are bent by means of mirrors; Fig. 5 shows an embodiment having a plurality of detection devices one next to the other with an electronic evaluation device; Fig. 6 shows the installation of the detection devices according to Figures 1 to 5 in a machine having a continuous feed shaft with a subsequent separation device; Fig. 7 and 8 show the installation of the devices according to Fig. 1 to 5 downstream of an opening roll; Fig. 8 shows an arrangement in which the two inspection stations have been inter-changed; Fig. 9 shows the installation of a polar-isation camera at an opening roll with subsequent separation; and Fig. 10 shows the installation of both cameras downstream of the opening roll.

With reference to Fig. 1, an inspection channel 1 has transparent walls 3 in the inspection region 2, through which fibre tufts 4 and the foreign bodies 5 to be detected flow. Two cameras 6, one on each side, are directed into the channel and on the respective other side meet a background sheet 7 of the material colour. For illumination there are used, for example, luminescent tubes 8 which radiate white non-polarised light in the visible wavelength range. A further luminescent tube 9 illuminates the background sheet 7. The light reflected by the fibre tufts 4 or foreign bodies 5 is received by the cameras 6 and analysed in respect of brightness and colour in the evaluator 10. Preferably the cameras are here able to receive the light in channels in the red, green or blue wavelength range and process it further separately, but in a simple case the use of black/white cameras is also possible if their sensitivity is limited to the visible part of the spectrum, for example by the use of filters.

Using one or more further illumination units 11, preferably arranged in a line over the working width, polarised light is then, in addition, applied to the fibre material at a further inspection station 12. The polarised light is generated, for example, by means of polarisation filters 13. In order not to influence the colour detection, here there is used a wavelength from the invisible part of the spectrum, for example infrared light. The red, green or blue channels of the cameras 6 do not react to that light, so that the distance between the inspection stations 2 and 12 can be selected to be very closely adjacent. The polarised infrared light is then reflected by shiny plastics bodies 14 and received on each side of the channel by two further cameras 15 and 16, which are in turn sensitive only to infrared light but not to light in the visible wavelength range. At least one of those cameras 15 has a further polarisation filter 17 which blocks the reflected light (polarised) and transmits only the diffuse reflection (non-polarised) . The other camera either has no polarisation filter or has a polarisation filter 35 which is arranged rotated through with respect to the polarisation filter 17. Comparison of the signals of those two cameras 15 and 16 with one another in an evaluator 18 supplies, for example by subtraction, an image which describes the degree of gloss of the surface. Glossy surfaces indicate synthetic materials and lead to subsequent separation, while matt surfaces, for example fibre material, are not detected.

Both cameras for the infrared wavelength range must be aligned very accurately with respect to one another, so that they generate a pixel-synchronous image on both signals.

In another embodiment shown in Fig. 2, both sensors of the cameras 15 and 16 are housed in one camera housing 19. These sensors are aligned with respect to one another behind the common lens system 20 or are arranged a spatially fixed distance apart, for example on a chip.

This simplifies alignment of the cameras, because it is then no longer necessary to align the two cameras with respect to one another. The polarisation filter 17, 35 is likewise mounted in the housing behind the lens system.

Alternatively, the polarisation in this camera is effected by means of prisms or glass surfaces. If both channels of this camera are each equipped with their own polarisation filter in directions orthogonal to one another, there is obtained a camera with which it is possible to analyse the polarisation state of the received light.

In the embodiment of Fig. 3, the channels of the colour camera are combined with the two infrared channels of the polarisation camera in one housing 22. The sensors for brightness and colour detection of the cameras 6, together with the polarisation state sensors of the camera 19, are positioned behind a lens and aligned with respect to one another or positioned in a fixed spatial arrange-ment with respect to one another. The distribution of the incident light between the individual sensors is effected, for example, by way of beam splitters, prisms or filters.

The inspection stations 2 and 12 and the components of the illumination modules 7, 8, 9, 11 and 13 are then also combined. At an inspection station 21, illumination is effected simultaneously with white visible non-polarised light and with polarised light outside the visible wavelength range. The evaluator 23 is then able to process both the signals of the brightness or colour sensors and the signals of the polarisation state sensors which are sensitive to infrared light.

A particular advantage is obtained here if there is used for the brightness and colour detection with non-polarised light white light in the visible wavelength range and if there is used for the illumination with polarised light illumination with infrared light. A particular feature of colour detection is that, undesirably, it also detects and separates further components of the cotton, such as stems and leaf residues, because these are very high-contrast and dark. This results in large amounts of waste. In the infrared wavelength range those bodies are light-coloured by virtue of their reflective properties. By comparing the brightness and colour signals with at least one of the infrared signals in an evaluator 23 it is possible to avoid detecting and separating those stems or leaf residues.

Fig. 4 shows an embodiment in which the camera lines of sight are bent by means of mirrors 24 to reduce the overall amount of space required.

In the case of large channel widths it can be advantageous to distribute a plurality of detection devices in accordance with Figures 1 to 4 over the working width so that each detection device is responsible for only one section of the channel. It is also possible, however, that for each section both detection methods can -10 -be realised using only one detector and one evaluation unit. Fig. 5 shows such an embodiment, viewed with the material transport direction perpendicular to the plane of the paper, in which a plurality of detection devices 22 are arranged one next to the other in order to cover the large working width. The components 7, 8, 9, 11 and 13 according to Fig. 3 are combined in the illumination modules 25.

Fig. 6 shows the integration of any of the detection devices according to Figures 1 to 5 in a machine having a continuous feed shaft with a subsequent separation device.

The detection device is supplemented by a device capable of detecting transparent or semi-transparent or fluor-escent foreign bodies using polarised transmitted light 28 in combination with UV light 27. For that purpose, a normal colour camera 26 is used. By means of the nozzle beam 29, detected foreign bodies are transported out of the inspection stations 33 and 30 into the waste chamber 31 whence they are transported out of the machine by means of a cellular wheel sluice 32.

Fig. 7 shows the integration of any of the devices according to Figures 1 to 5 after an opening roll. Fig. 8 is a further embodiment in which the two inspection stations have been interchanged.

In the embodiment of Fig. 9, there is illustrated the integration of a polarisation camera 19 on an opening roll with subsequent separation. The polarisation camera 19 does not detect brightness or colour differences but detects solely differences in the degree of gloss and is thereby able to detect foreign bodies having a different degree of gloss. The coloured foreign bodies are detected and separated by the camera downstream of the opening -11 -roll. The transparent and UV-sensitive foreign bodies are also detected and separated at the inspection station downstream of the opening roll.

In the embodiment of Fig. 10, both cameras 22 and 26 are integrated downstream of the opening roll.

Claims

-12 -Claims 1. A device in spinning room preparation for detecting foreign bodies made of plastics in or between tufts of fibre material, comprising illumination means for illuminating the fibre tufts and the foreign bodies with non-polarised light of one wavelength range and with polarised light of a different wavelength range in such a way that both kinds of light can be used together in a machine at closely adjacent positions.
2. A device according to claim 1, wherein said closely adjacent positions comprise first and second inspection stations, each permitting illumination of the fibre tufts.
3. A device according to claim 2, wherein the first inspection station is arranged to serve for illuminating the tufts with the non-polarised light and the second inspection station is arranged to serve for illuminating the tufts with the polarised light.
4. A device according to claim 2 or claim 3, wherein the two inspection stations are identically constructed.
5. A device according to any one of claims 1 to 4, wherein the illumination means comprises a source of non-polarised light of one wavelength range and a source of polarised light of a different wavelength range.
6. A device according to claim 5, comprising a source of non-polarised light of one wavelength range and a source of polarised light of a different wavelength range arranged in a common housing.
7. A device according to any one of claims 1 to 6, whereindetector devices for the non-polarised light of the one wavelength range are arranged in a common housing -13 -together with the sensors for the polarised light of the different wavelength range.
8. A device according to any one of claims 1 to 7, wherein, for the non-polarised light, wavelengths from the visible part of the spectrum are used.
9. A device according to any one of claims 1 to 8 wherein, for the polarised light, wavelengths from the infrared part of the spectrum are used.
10. A device according to any one of claims 1 to 9, wherein the polarised light is substantially free of light of wavelengths in the visible part of the spectrum.
11. A device according to any one of claims 1 to 10, further comprising at least two detector devices for light of the wavelength of the polarised illumination light, at least one said detector device being arranged to block unaltered polarised light and detect non-polarised light and at least one other said detector being arranged to block non-polarised light and detect unaltered polarised light.
12. A device according to any one of claims 1 to 10, wherein to cover a large working width a plurality of detection devices operate in sections in parallel one next to the other.
13. A devices according to any one of claims 1 to 12, wherein to reduce the overall space required deflectors are present for deflecting the light before or after it passes through the fibre tufts.
14. A device according to any one of claims 1 to 13, further comprising an evaluation unit arranged to distinguish the fibre tufts from foreign bodies.
15. A device substantially as described herein with reference to and as illustrated by any of Figs. 1 to 10.

-14 -
16. A spinning preparation machine comprising a device according to any one of claims 1 to 15.
17. A spinning preparation machine according to claim 16, further comprising a device which operates with polarised transmitted light and/or UV light in a machine in order to maximise the reliability of detecting colourless foreign bodies.
18. A method for detecting foreign bodies of plastics materials from a stream of fibre material comprising illuminating the fibre material with non-polarised light of one wavelength and at the same or a closely adjacent location illuminating the fibre material at the same time with polarised light of a different wavelength.