Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1991-08-26
1993-01-26
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356430, G01N 2188
Patent
active
051824574
DESCRIPTION:
BRIEF SUMMARY
The invention involves a device for photo-electrically monitoring a moving yarn for irregularities, consisting of sensor heads connected in series in the direction of yarn movement, where both the first and second sensor heads are attached to a beam transmitter and a beam receiver.
It is known that different irregularities can have different effects on individual yarn during further processing or as the finished product. Slubs, for example, generally cause defects in further processing. A specific small number of projecting fibres, for example, could be tolerated for certain final uses of yarn. For this reason it would be beneficial if every defect could be recorded individually for an assessment of quality.
The photo-electric monitoring of a moving yarn is already known U.S. Pat. No. 729,635). Here a silhouette of the yarn group is converted into an electric signal, which nullifies the values existing below a cut-off limit and when there are values above the cut-off limit shuts off the textile machine. Further development has led to a continual increase in sensitivity. Yet, even with increased sensitivity small yarn defects could not be recorded because of the background noise. A yarn consists generally of individual fibers and, because of its surface, never displays a completely homogeneous, rounded cross-section. Twisting movements, uneven yarn movement and a not entirely level yarn thus produces a broader, more diffuse silhouette during the overshadowing then the actual yarn cross-section shows. This diffuse section of the silhouette is described as the basic noise of the moving yarn. Small defects are lost in this basic noise level. In practice this basic noise varies in value between 10 and 120% of the yarn cross-section.
No indications about the direction of the yarn and measurement of its irregularities are evident in the publication. Using all known devices and methods individual types of defects cannot be differentiated.
The objective of the invention is to make available a device to control a moving individual yarn, which differentiates irregularities recorded by type of defect, especially so-called slubs, or projecting fibres and/or thin or thick areas in monofilaments.
The invention achieved this by equipping both the first and second sensor heads with recesses, in which the cross sectional depth of the second sensor head recess is larger than the first sensor head recess.
On the first sensor head, sensitivity can be adjusted variably. Since the yarn is only slightly lowered into the recess, only major yarn irregularities, e.g. slubs, are detected by the first sensor head when it is set at high sensitivity. The second sensor head detects all occurrences, i.e., even broken fibers, which protrude above the upper edge of the recess. The yarn is, dependent on the level of detection, lowered into the recess of the second sensor head, so that various types of defects and irregularities in the yarn can be determined simultaneously in one pass.
No known method is as yet able to use exclusively the shadow cast by the moving yarn's projecting defects for signal evaluation and thus also for differentiation of defects.
Automatic distinguishing of various defects creates sorting possibilities and thus introduces certain advantages with regard to quality control of a yarn. Automatic controls are labor saving with regard to monitoring and the determination of defects, as well as providing an immediate assessment of the current production's actual quality.
There are various cross-sectional profiles, as, for example, V-shaped or rectangular cross-sections are suitable for gauging. Particularly advantageous in the cross-sectional depth of the second sensor head which is at least 1.02 times, in particular 2 -5 times, preferably 1.5-3 times deeper than the cross-sectional depth of the first sensor head. The width of the slot should be at least as large as the yarn cross-section, in particular 1.1-10 times, preferably 1.5-2 times larger. Using the invented device even thick areas in monofilaments can be determined
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patent: 4716942 (1988-01-01), Jensen et al.
patent: 4743749 (1988-05-01), Grundyu
patent: 4963757 (1990-10-01), Vanliefde et al.
patent: 4970402 (1990-11-01), Devuyst et al.
patent: 5036568 (1991-08-01), Goineau
Rhone-Poulenc Viscosuisse SA
Shami K.
Westin Edward P.
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