Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/89—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles
  • G01N21/8914—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined
  • G01N21/8915—Investigating the presence of flaws or contamination in moving material, e.g. running paper or textiles characterised by the material examined non-woven textile material

Definitions

• the invention relates to the detection of contaminants in a highly elongated textile material such as thread, yarn, sliver, roving etc.
• a highly elongated textile material such as thread, yarn, sliver, roving etc.
• it relates to an apparatus and a method for the detection of contaminants in an elongated textile material as described in the preamble of claim 1 and 11, respectively.
• US 4,739,176 discloses a related apparatus for detecting contaminants in a textile yarn.
• the yarn is guided through a narrow channel, illuminated from one side, and reflected light is measured in a detector located on the same side.
• the three remaining faces of the channel are formed by an insert made of a semi-opaque material that is illuminated from behind in order to provide for an evenly lighted background.
• Said three faces of the channel are separated from the yarn by a distance that is only about 2 to 4 times the mean yarn diameter, in order to prevent shadowing problems, and to improve uniformity and diffuseness of the illumination.
• the illumination of the semi-opaque background and the material of the background are chosen to match the light reflected from the yarn, such that variations in thickness of the uncontaminated yarn do not affect the amount of light perceived by the detector.
• US 5,371,584 shows a related apparatus in which a yarn is guided through a channel that is less constricted than the channel shown in US 4,739,176, but necessitates both light sources for illuminating the yarn and a separate light source for illuminating a background surface.
• the apparatus is made of a transparent body provided with a mirror-like surface. This is meant to flood the entire body with light such that the zone of measurement is diffusely illuminated and the yarn is illuminated from all sides. In order to compensate for variations in the yarn, it is necessary to control the illumination of at least one of the light sources according to an uncontaminated reference yarn.
• a variation in the amount of light reaching the detecting means from the textile material is at least approximately compensated by a corresponding variation in the amount of light reaching the detecting means from the reflecting means, the reflecting means being opaque.
• the reflecting means which forms a background against which the detecting means observes the textile material is not illuminated from behind.
• the reflecting means comprises a planar surface exhibiting predominantly lambertian reflection characteristics. This offers the advantage that a channel or a gap in which the textile material travels can be made larger than a channel that closely surrounds the textile material from three sides. It is therefore easier to insert the textile material, e.g. a yarn into such a larger gap. Since a narrow channel is not required, the yarn can be inserted into the inventive apparatus in a simple way.
• the planar surface is preferably made of a ceramic surface, and preferably exhibits lambertian reflection to a degree of 85% to 90% or more.
• a detector unit comprises an active section that contains or encloses the illuminating means and the detecting means.
• the active section is separated or distanced from the reflecting means by a gap in which the textile material is guidable.
• the illuminating means illuminates both the textile material and the reflecting means from the same side, allowing for a simple and robust arrangement with a minimum of wiring. No relative adjustment of separate illuminating means for the textile material and for the background is required.
• the illuminating means are white light emitting diodes. This allows the apparatus to detect contaminations of almost any colour.
• a further preferred embodiment of the invention comprises exactly two light emitting diodes (LEDs), providing optimal properties with regard to shadowing.
• Figure 1 schematically shows an arrangement of main elements of the invention in a plane that is parallel to a textile material; and Figure 2 schematically shows a cross section of a detector unit according to the invention.
• Figure 1 schematically shows an arrangement of main elements of the invention in a plane that is parallel to a product such as a textile material 3.
• the textile material is typically elongated, in particular a yarn, sliver, roving, filament or strand filament, etc.
• the material is made of e.g. cotton, wool, polyester or other natural or synthetic fibres.
• a reflecting plate 1 is arranged in parallel to a filter 2. Both the reflecting plate 1 and the filter 2 are essentially planar and form a yarn guide path or gap 9 through which a yarn 3 or a similar highly elongated textile product moves.
• the yarn 3 is guided by elements not shown.
• the light emitting diodes 4 Arranged on one side of the filter 2 and separated from the gap 9 by the filter 2 are light emitting diodes 4 and a detector 5.
• the light emitting diodes 4 emit light through the filter 2 at an angle onto both the yarn 3 and the reflecting plate 1. Separating means, not shown, prevent light emitted from the light emitting diodes 4 to leak into the detector 5 without having been reflected by the yarn 3 or the reflecting plate 1. The emitted light is reflected from both the yarn 3 and the reflecting plate 1 through the filter 2 and detected by the detector 5.
• the detector 5 is preferably a photodetector or a RGB (red/green/blue) detector.
• Analog signals from the detector 5 are conditioned in a signal conditioning unit 6 and the conditioned signals are processed in a signal processing unit 7 and converted into a standardised units of measurements. Based on these converted signals, a supervisory control system decides on whether contaminations are tolerable or whether an observed section of the 3 should be cut out.
• Figure 2 schematically shows a cross section of a detector unit 10 in a cross section perpendicular to the direction of movement of the yarn 3.
• the light emitting diode 4 and detector 5 are contained in an active section 8 of the detector unit 10.
• the detector unit 10 also comprises the reflecting plate 1 which is separated or distanced from the active section 8 by the gap 9.
• a gap size G preferably is preferably in the range from 1mm (millimeters) or 2 mm to 5 mm or 10 mm and preferably at least approximately equal to 2.5 mm. Larger gaps reduce the sensitivity of the apparatus, since light is distributed over a larger area and interference from outside light increases. Narrower gaps make the insertion of the yarn and the cleaning of the apparatus more difficult an increase rubbing of the yarn when running through the measurement volume.
• the filter 2 is a transparent sheet or plate of glass or plastic. It protects the light emitting diodes 4 and the detector 5 from the ambience and optionally filters the light and/or optimises the diffusion of light, minimising shadowing effects within the observation region of the detector 5.
• the filter 2 is not made from a single sheet but is split into separate segments for each of the light emitting diodes 4 and for the detector 5. In a further preferred embodiment of the invention, one or more of these segments are omitted altogether.
• the reflecting plate 1 is preferably a flat sheet having a surface with predominantly lambertian reflection characteristics, preferably to a degree of 85% to 90% or more. This is in contrast to specular or mirror-like reflection characteristics.
• a measurement field corresponding to a minimum size of the reflecting plate 1 has a length L parallel to the yarn 3 of ca. 5 mm to 11 mm and preferably at least approximately equal to 8 mm, and a width W normal to the yarn 3 of ca. 5 mm to 11 mm and preferably at least approximately equal to 8 mm.
• the reflecting plate 1 forms a background against which the yarn 3 is seen.
• the reflection characteristics of the reflecting plate 1 match those of the yarn 3.
• the amount of light reflected from the yarn 3 increases.
• the arrangement is insensitive to the dimensions, in particular the thickness of the yarn 3. For example, the following variations in diameter and associated changes in observed light flux have been measured.
• the reference diameter is 0.07mm.
• the second column shows the results for an LED arrangement as in Figures 1 and 2.
• the third column corresponds to the light emitting diodes 4 being arranged in a plane that is parallel to and comprises the yarn 3, i.e. the plane of the paper in Figure 1.
• a reference length of yarn 3, preferably having no contaminants is observed, e.g. several tens of meters, e.g. 32 m. This is done e.g. at start up before a production run. A maximum ratio of the variation of instantaneous values around constant or slowly changing average values is determined. Thresholds for the detection of contaminations are set according to this ratio.
• contaminants are classified according to a plurality of parameters associated with them.
• the production of the yarn is then controlled to remove only some of the contaminants, in accordance with their classification.
• the signal intensity corresponding to the light received by the detector 5 usually varies between a maximum determined by the uncontaminated yarn 3, and a minimum corresponding to a completely black yarn 3.
• a length of the contamination is stored together with an associated relative brightness or colour shade of the contamination.
• the set of lengths and brightness values may be plotted on an XY-Graph.
• the stored data is analysed manually or automatically to control further processing of the yarn 3.
• Contaminants of different sizes and colour or intensity are cleared selectively.
• a seed coat causes a typical, relatively high intensity variation but only for a typical, relatively small length of the yarn 3. Since seed coats fall out at later stages of the processing of the yarn 3, they need not be removed.
• the RGB detector comprises photodetectors with red, green and blue filters that determine corresponding primary colour components of the reflected light.
• the colour components observed on the reference length of the yarn are measured and serve as reference values. During normal operation of the inventive apparatus, deviations from this reference that exceed given thresholds indicate the detection of contaminants.
• each light emitting diode 4 is associated with a separate transparent medium or filter that shields the light emitting diode 4 from the environment and optionally diffuses or scatters the emitted light.
• the light emitting diodes 4 are arranged in a plane that is perpendicular, i.e. normal to the direction of the yarn 3, i.e. the plane of the paper in Figure 2. For each of the diodes, a main axis of an emitted light beam lies in said perpendicular plane.
• the light emitting diodes 4 are arranged in a plane that is parallel to and comprises the yarn 3, i.e. the plane of the paper in Figure 1. For each of the diodes, a main axis of an emitted light beam lies in said parallel plane as well.
• the light emitting diodes 4 can be of any colour, however white LEDs are preferred since they allow the detection of a wide range of contaminants. Alternatively, other light sources than LEDs may be used without altering the essence of the invention.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
• Treatment Of Fiber Materials (AREA)

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• 2003
  • 2003-02-14 EP EP03815845A patent/EP1592963A1/de not_active Ceased
  • 2003-02-14 AU AU2003303911A patent/AU2003303911A1/en not_active Abandoned
  • 2003-02-14 WO PCT/IB2003/000506 patent/WO2004072625A1/en not_active Application Discontinuation

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