Optics: measuring and testing – Inspection of flaws or impurities – Textile inspection
Reexamination Certificate
2002-12-06
2004-07-06
Stafira, Michael P. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Textile inspection
C356S238200
Reexamination Certificate
active
06760102
ABSTRACT:
BACKGROUND OF THE INVENTION
1) Field of the Invention
This invention relates to a method and apparatus for continuous detection and localization of yarn defects in a yarn sheet which is traveling in a plane and which is scanned by light beams for yarn defects such as protruding filaments, broken filaments, fuzzballs, stripbacks, ringers and the like, each light beam interruption triggered by such a yarn defect, thereby triggering a detector pulse.
2) Prior Art
The monitoring of traveling yarns for diameter fluctuations and particularly for protruding filaments, yarn defects, i.e. broken filaments, fuzzballs, ringers, stripbacks and the like, in the production of yarns in the manufactured fiber or textile industry using optical detector devices such as for example light barriers is known.
Such a device for monitoring a single traveling thread or yarn for diameter fluctuations and protruding filaments using a light barrier operating in the infrared region is described in DE 29 33 297 A.
Similar light barriers are used to monitor sheets of some hundred unwinding yarns in the production of warp beams. With this procedure, only relatively coarse yarn defects and broken yarn are identified as defects; these light barriers are unable to recognize broken individual filaments in individual yarns. Localization of the yarn defect at right angles to the yarn direction is generally only possible at huge cost and inconvenience, if at all.
EP 0 296 469 B1 discloses a process for determining quality characteristics of traveling yarns by using defect counters to determine the number of yarn irregularities. The yarn passes through at least three successive defect sensors of the same type whose counting pulses emitted on passage of a yarn section of the freely chosen length L are converted into a length-based average R by disregarding from the averaging any greatly deviant individual measurements as spurious values. The apparatus used to carry out the process consists of at least three defect sensors disposed consecutively in the yarn path, means for measuring the traversing yarn length L and an arithmetic processing unit which sums the counting pulses separately for each sensor to form pulse totals and stores these pulse total values. The totals obtained are tested for spurious values according to predetermined criteria and such values are eliminated. Useful means for measuring the yarn length include any arrangement known for this purpose, for example a measuring roller of a certain circumference which is rotated without slippage by the traveling yarn and whose number of revolutions is recorded. To monitor a sheet of yarn, every individual yarn has to be inspected by such apparatus; the cost is accordingly enormous.
DE 195 26 646 A1 discloses a process for monitoring a traveling yarn sheet by passing the yarn sheet over guide bars upstream and downstream of the monitoring site and sending at least one light beam at right angles to the traveling direction of the yarn sheet and parallel to the yarn sheet plane to photoreceptors. The signals from the photoreceptors are evaluated by an electronic evaluating unit and recorded. At least four photoreceptors are used, of which at least two are disposed successively in the yarn traveling direction and at least two above each other in such a way that there is at least one photoreceptor below and at least one photoreceptor above the yarn sheet plane. All the photoreceptors are disposed in such a way that they form superposed pairs and all the pairs are disposed one behind the other. This known apparatus preferably employs 4 quadrant photoreceptors or multisegmental photocells. The monitoring arrangement is formed by a light source, which can be a laser light source, a lens for parallelizing the light beam, a diaphragm for determining the light beam cross section, a further diaphragm for intercepting stray rays, a lens for focusing light beams and a 4 quadrant photoreceptor or a multisegmental photocell. The technical complexity of this apparatus is enormous. A specific method for localizing a yarn defect at right angles to the yarn direction is not described.
DE 38 32 984 C2 discloses a process and apparatus for indicating broken ends in a yarn sheet traveling in a plane by scanning the yarn sheet with a laser beam at right angles to the traveling direction of the yarn sheet in continually repeated passes and counting the light pulses reflected by the individual ends per passage by means of detectors. The number of light pulses is compared with a target value for the number of individual ends and deviations from the target value are indicated. For this, a multiplicity of detectors are disposed side by side substantially equal distances apart in a row which is perpendicular to the yarn traveling direction and in a plane which is parallel to the yarn sheet plane, in such a way that reception areas overlap. The detectors are oriented in an identical angle, the backbeam angle, to the line of incidence of a laser beam reflected by a rotating mirror, with the yarn sheet. The laser beam is disposed relative to the yarn sheet and relative to the row of detectors in such a way that the angle of incidence of the laser beam reflected by the rotating mirror on the yarn sheet and the backbeam angle are substantially the same. At least three and preferably at least five passes are grouped together in a cycle and the light pulses are counted per pass and compared with the predetermined target value for the number of individual ends. Absent agreement between the two values, a defect signal is generated and counted in a counter. At the end of each cycle, the final value of the counter is compared with a predetermined limiting value and when the limiting value is reached or exceeded the yarn sheet is stopped. Again, the technical complexity of this process and apparatus is comparatively large.
WO93/06466 describes a process for detecting and counting yarn defects in a yarn segment using a camera, a computer and an image processing program. The yarn is recorded by the camera with an intensity which depends on the thickness of the yarn. The recorded image is digitized in the computer by the image processing program and low-contrast points are filtered out. The points which remain are grouped together into continuous areas whose size is categorized into predetermined size classes and stored. The process makes it possible to count yarn defects, for example. yarn impurities, objectively and reproducibly. This process is not intended for inspecting a fast-traveling yarn sheet for defects in individual ends.
WO93/19359 discloses a process and apparatus for detecting impurities in a textile test material. For this, the test material is illuminated for at least two locations and the light reflected by the test material is measured by receptors and in addition to the reflection the diameter or diameter changes of the test material are measured. The measured signals obtained are combined and the resulting signal is examined for deviations from a predetermined value. If a deviation is ascertained, an impurity is present in the test material. The checking of a fast-traveling yarn sheet for yarn defects is not possible by this process and the apparatus intended for it.
It is also known for a yarn sheet to be monitored using commercially available single light barriers and to be stopped in the event of a yarn defect occurring. In this process, the operating personnel subsequently has to search for the yarn defect and to cut it out, for example, and subsequently to piece the yarn back together by means of a knot. The only information to guide the search for the yarn defect that the operating personnel has available is that the position of the yarn defect is localized in the yarn traveling direction. This position follows from the original traveling speed of the yarn sheet and the speed deceleration to stopping by the brakes which stop the yarn sheet. There is no information about the position of the yarn defect at right angles to the traveling direction of the yarn sheet, so that the op
Arteva Technologies, S.a.r.l.
Clements Gregory N.
Stafira Michael P.
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