Optics: measuring and testing – By monitoring of webs or thread
Patent
1991-08-02
1993-06-22
McGraw, Vincent P.
Optics: measuring and testing
By monitoring of webs or thread
250561, 250571, G01N 2184
Patent
active
052219607
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to an opto-electronic yarn detector apparatus.
An opto-electronic yarn detector in prior public use for detecting the passage of a yarn in an annular gap of a yarn storage and feeder device comprises a light source in the form of a light-emitting diode, and a receiver in the form of a photodiode or a phototransistor. A collective lens disposed opposite the receiver surface is designed to focus parallel light beams and views of a cylindrical detection field of infinite depth. The focus of the collective lens on the side of the yarn is located at infinity. The receiver or detector is set to a threshold value. A predetermined change of the brightness on the receiver surface results in the generation of a working signal, the light emitted, for example reflected, by the respective object in the detection field being uniformly distributed over the receiver surface. The working signals are extremely weak, requiring extensive measures to be taken for their amplification and noise suppression so as to permit the signals to be further processed. In view of the high yarn speeds in modern textile machinery, detector devices of this type are only of limited usefulness. They are particularly affected by extraneous light effects and contamination. A grave disadvantage is the tendency to produce false signals in response to the presence of fluff or lint tufts, because the apparatus is incapable of recognizing the difference between the yarn and such foreign matter, even when the latter reflects the light less strongly than the yarn. This is because a small amount of foreign matter at a small distance and a greater amount of foreign matter at a greater distance reflect the same amount of light as a yarn located at the proper distance.
U.S. Pat. No. 3,401,267 discloses an opto-electronic yarn detector for warp yarns in a weaving machine, in which the depth of the cylindrical detection field is equal to the width of the woven fabric. Light reflected by a warp yarn or by a greater amount of foreign matter is concentrated by a collective lens and uniformly distributed on the receiver surface. The working signal is generated when the light is of sufficient brightness.
Yarn detectors which are known from U.S. Pat. No. 4,300,599, U.S. Pat. No. 3,853,408 and U.S. Pat. No. 4,378,161 operate in the same way in principle. As the yarn passes the working signal in these yarn detectors is derived only from differences in brightness on the receiver surface.
The weakness of the working signal and the susceptabiilty to the presence of foreign matter result in these yarn detectors from the principle of viewing an excessively deep detection field virtually extending to infinity, and of generating signals on the basis of brightness variations on the receiver surface, a threshold value being used as a basis here.
In an apparatus as known from EP-A3-0 188 760 an object line, e.g. a bar code, on a moving material web is scanned by means of an imaging optics and the information contained in the object line is determined.
In accordance with EP-A-3-0 162 134, two-dimensional strips of the woven fabric are continuously scanned in a weaving machine by means of a moving scanning head to detect texture defects. An optics suitable for this purpose is provided on the side of the detector. To obtain information from each strip, the luminosity value on a scanning line is evaluated.
The method known from EP-A2-0 271 728 for measuring and/or monitoring yarn characteristics comprises the step of taking with the help of an image sensor the instantaneous picture of a yarn section and converting the latter to detect either thickness, circularity, twisting, projecting fibers or extension. The stationary yarn is examined, or when the latter moves in longitudinal direction, either an instantaneous picture is taken, or a stroboscope is used for obtaining a series of pictures, and the pictures are converted.
In the three last-mentioned cases the information that can be taken from the image of the present object is determined. The o
REFERENCES:
patent: 3853408 (1974-12-01), Kaalverink
patent: 4300599 (1981-11-01), Wueger
patent: 4378161 (1983-03-01), Maddox
Akerlind Bo
Fredriksson Lars-Berno
Hellstrom Jerker
Iro AB
McGraw Vincent P.
LandOfFree
Opto-electronic detector apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Opto-electronic detector apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Opto-electronic detector apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1443986