Optics: measuring and testing – By monitoring of webs or thread – For flaws or imperfections
Reexamination Certificate
1999-01-29
2001-05-01
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By monitoring of webs or thread
For flaws or imperfections
C356S238200
Reexamination Certificate
active
06226088
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a system for detecting defects in a moving web. Webs, for example textile webs, may often include defects, for example yarn width variations, mispicks, double picks, machine stop marks, and pile irregularities, which are not readily detectable by a human operator. These defects sometimes become apparent only during downstream processing steps, for example dying, or after the fabric is shipped to a customer. According, it is desirable to detect such defects at a relatively early production stage.
Automatic web defect detection systems are known which employ photodetectors disposed with respect to a light source and the moving web to detect defects from the interference between the web and light from the light source. Calibration of such systems so that these photodetectors receive an optimal light signal may sometimes be difficult, particularly as the web or ambient conditions change.
SUMMARY OF THE INVENTION
The present invention recognizes and addresses disadvantages of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide an improved optical web detection system.
This and other objects are achieved in one preferred embodiment of the present invention by an optical web defect detection system. The system comprises a light source and a detector disposed with respect to the light source so that the detector receives light modulated by a moving web and emitted by the light source at an oblique angle with respect to a plane defined by the web. The detector outputs a signal corresponding at least in part to the modulated light. A control mechanism is in operative communication with the detector. The control mechanism receives the signal to detect a defect in the web based on the signal.
In another preferred embodiment, an optical web defect detection system includes a light source and a first detector disposed with respect to the light source, and at a first distance from a moving web, so that it receives light modulated by the web. The first detector outputs a first signal corresponding at least in part to the first modulated light. A second detector is disposed with respect to the light source, and at a second distance from the web greater than the first distance, so that the second detector receives light modulated by the web. The second detector outputs a second signal corresponding at least in part to the modulated light. A control mechanism is in operative communication with the first detector and the second detector. The control mechanism receives the first signal and the second signal to detect defects in the web based thereon.
In another preferred embodiment, an optical web defect detection system includes a light source and a detector disposed with respect to the light source so that the detector receives light modulated by a moving web proximate the light source. The detector outputs a signal corresponding at least in part to the modulated light. A control mechanism is in operative communication with the detector and the adjustment mechanism. The control mechanism receives the signal to detect a defect in the web based thereon. A shift mechanism is in operative communication with the detector and is configured to reciprocally move the detector in a path parallel to a plane defined by the web and disposed at an oblique angle with respect to a line transverse to the moving direction of the web.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.
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Nelson Mullins Riley & Scarborough LLP
Pham Hoa Q.
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