WO2004072625A1

WO2004072625A1 - Detection of contaminants in an elongated textile material

Info

Publication number: WO2004072625A1
Application number: PCT/IB2003/000506
Authority: WO
Inventors: Shekaripuram Narayanaswamy Ramachandran; Kallidaikurichi Krishnan Venkataraman; Appavu Pavendhan
Original assignee: Premier Evolvics Pvt. Ltd.
Priority date: 2003-02-14
Filing date: 2003-02-14
Publication date: 2004-08-26
Also published as: AU2003303911A1; EP1592963A1

Abstract

An apparatus and method for the detection of contaminants in a elongated textile material (3) use illuminating means (4) for illuminating both the textile material (3) and a reflecting means (1) and detecting means (5) for detecting an amount of light. The detecting means (5) is arranged to detect a total amount of light reflected from the textile material (3) and from the reflecting means (1). The reflecting means (1) is opaque and exhibits diffuse reflection. A variation of textile material dimensions causes a variation in the amount of light reaching the detecting means (5) from the textile material (3) that is compensated by a corresponding variation in the amount of light reaching the detecting means (5) from the reflecting means (1).

Description

DETECTION OF CONTAMINANTS IN AN ELONGATED

TEXTILE MATERIAL

FIELD OF THE INVENTION

The invention relates to the detection of contaminants in a highly elongated textile material such as thread, yarn, sliver, roving etc. In particular, 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.

BACKGROUND OF THE INVENTION

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.

DESCRIPTION OF THE INVENTION

It is an object of the invention to create an apparatus and a method for the detection of contaminants in an elongated textile product or material of the type mentioned initially, which is easier to maintain in operation, has a simple structure and is therefore cost-efficient to build and operate.

These objects are achieved by an apparatus and a method for the detection of contaminants in an elongated textile material according to the claims 1 and 11.

According to the invention, 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. As a result, the reflecting means, which forms a background against which the detecting means observes the textile material is not illuminated from behind.

Advantages are that no separate illuminating means shining through a semi- transparent or semi-opaque background are required. Requirements on the background material are relaxed, since transparency and the attainment of a specific degree of transparency are irrelevant. Controlling background lighting separately is not necessary either.

In a preferred embodiment of the invention, 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.

In a further preferred embodiment of the invention, 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. In a further preferred embodiment of the invention, 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.

Further preferred embodiments are evident from the dependent patent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the attached drawings, in which:

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.

The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

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. For the purpose of the following exemplary embodiment, reference shall be made to a yarn 3, but it is understood that the invention applies to other elongated textile materials as well. 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. 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. In another preferred embodiment of the invention, 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.

From the point of view of the light emitting diodes 4 and detector 5, 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. As a result, when a thicker section of the yarn passes in a measurement zone in front of the detector 5, the amount of light reflected from the yarn 3 increases. However, since a corresponding part of the background is occluded by the yarn 3, and less light reflected from the reflecting plate 1 reaches the detector 5. The net effect is that only a small change in the detected amount of light occurs, ideally no change at all. That is, 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.

When a contaminant or foreign particle is present in or on the yarn 3, there is a change in light reflected from the yarn 3 and a corresponding change in the signal output by the detector 5 and signal conditioning unit 6.

In a preferred variant of the invention, 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.

In a further preferred variant of the invention, 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. For example, 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. For each contamination, 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. For example, 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.

When a contaminant or foreign particle is present, there also is a change in spectrum of the reflected light, which can be detected by an RGB detector. 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.

In the arrangement shown in Figure 1, the light emitting diodes 4 are arranged to shine through the same filter 2 through which the reflected light reaches the detector 5. In another preferred embodiment of the invention, 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.

In the arrangement shown in Figure 1, 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. In another preferred embodiment of the invention (not shown in the figures), 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.

While the invention has been described in present preferred embodiments of the invention, it is distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practised within the scope of the claims.

List of designations

1 reflecting plate

2 filter

3 yarn

4 light emitting diode

5 detector

6 signal conditioning unit

7 signal processing unit

8 active section

9 gap

10 detector unit

W width

L length

G gap size

Claims

P A T E N T C L A I M S

1. Apparatus for the detection of contaminants in a elongated textile material (3), comprising illuminating means (4) for illuminating both the textile material (3) and a reflecting means (1) and detecting means (5) for detecting an amount of light, characterised in that the detecting means (5) is arranged to detect a total amount of light reflected from the textile material (3) and from the reflecting means (1), and that the reflecting means (1) is opaque and exhibits diffuse reflection, where a variation of textile material dimensions causes a variation in the amount of light reaching the detecting means (5) from the textile material (3) that is at least approximately compensated by a corresponding variation in the amount of light reaching the detecting means (5) from the reflecting means (1).

2. Apparatus according to claim 1, wherein the reflecting means (1) comprises a planar surface exhibiting predominantly lambertian reflection.

3. Apparatus according to claim 2, wherein the reflecting means (1) is a flat plate.

4. Apparatus according to claim 3, wherein the reflecting means (1) is a ceramic plate.

5. Apparatus according to one of the preceding claims, wherein a surface of the reflecting means (1) that is oriented towards the illuminating means (4) and the detecting means (5) exhibits lambertian reflection of 85% to 90% or of more than 90%.

6. Apparatus according to one of the preceding claims, comprising a detector unit

(10), the detector unit (10) comprising an active section (8) that contains the illuminating means (4) and the detecting means (5), the active section (8) being separated from the reflecting means (1) by a gap (9) in which the textile material (3) is guidable.

7. Apparatus according to one of the preceding claims, where the illuminating means (4) are white light emitting diodes.

8. Apparatus according to one of the preceding claims, where the illuminating means (4) are exactly two light emitting diodes (4).

9. Apparatus according to claim 8, where the two light emitting diodes (4) are arranged in a plane that is perpendicular to the textile material (3).

10. Apparatus according to claim 8, where the two light emitting diodes (4) are arranged in a plane comprising the textile material (3).

11. Method for the detection of contaminants in an elongated textile material (3), comprising illuminating both the textile material (3) and a reflecting means (1) and detecting an amount of light, characterised in that a total amount of light that is reflected from the textile material (3) and from the reflecting means (1) is detected, and that the reflecting means (1) is opaque and exhibits diffuse reflection, and that a variation of textile material dimensions causes a variation in the amount of light reaching the detecting means (5) from the textile material

(3) that is compensated by a corresponding variation in the amount of light reaching the detecting means (5) from the reflecting means (1).

12. Method according to claim 11, wherein a variation in the amount of light reaching the detecting means (5) indicates the presence of contaminants in the textile material (3).

13. Method according to claim 12, wherein a contaminant is classified according to a length of the contaminant along the yarn (3) and the amount of light associated with the contaminant.