Process to detect and count yarn defects having a color backgrou

Details Process to detect and count yarn defects having a color backgrou Process to detect and count yarn defects having a color backgrou

1994-03-22

1995-05-30

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356238, 242 36, G01N 2188

Patent

active

054204399

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

Gravimetric processes and manual counting processes were known in the past for the detection of yarn defects caused by impurities. Gravimetric processes are based on the collection and weighing of eliminated trash particles during the spinning process, e.g. on a rotor spinning machine. This does however not indicate how much trash still remains in the finished yarn nor the type of impurities remaining.
Also known are manual counting processes to ascertain how many trash particles are in the yarn. For this purpose the spun yarn is knit on a circular knitting machine and a certain surface is cut out of the knit material. A grid is placed on the cut-out surface and the number of trash particles in the individual areas is counted. The disadvantage of this system is the great amount of time necessary to prepare the knit material and then to count the particles. It is also a disadvantage that the success of the process depends very much on the accuracy of person doing the counting. Comparisons have shown that examinations of the same knit material by different persons show very different counting results.


OBJECTS OF THE INVENTION

It is a principal object of this invention to create a rapid, objective and reproducible method to count the trash particles and other yarn defects or impurities in the yarn. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
Advantageous embodiments of the invention are shown in the accompanying drawings.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a layout of the devices used for optical yarn analysis;
FIG. 2 shows a measuring instrument for yarn analysis;
FIG. 3 shows a winding device;
FIG. 4 shows a flow-chart for the control of the device for optical yarn analysis; and
FIG. 5 shows the results of a trash analysis of the yarn.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, and not as a limitation of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Additionally, the numbering of components in the drawings is consistent throughout the application, with the same components having the same number in each of the drawings.
FIG. 1 shows a schematic sketch of a device for optical yarn analysis. The yarn to be examined is wound up on a bobbin 1. For the examination the yarn is introduced through an opening into a housing 2. In order to avoid influences due to external light, the housing 2 is made light-tight in an advantageous embodiment. This ensures that a wind-up unit 3 can be illuminated evenly in incident light by a light source 4. The light-tight housing 2 prevents any additional light sources from influencing the wind-up unit 3 from the outside and thus possibly to cast shadows which the system would erroneously recognize to be yarn defects. The wind-up unit 3 is either a conventional yarn plate or an automatically driven device according to the invention such as described in further detail in FIGS. 2, 3, and 4.
The light source 4 in this case is advantageously a fluorescent bulb. Two concentric ring-shaped fluorescent bulbs have shown to be especially well suited here. Such a light source 4 ensures even, shadowless illumination of a testing surface on the wind-up unit 3. If the light source 4 is an infrared light, trash and other yarn irregularities which are inside the yarn, and not only those located on the outside and on the visible side of the yarn, can be detected. A camera 5 is installed above the light source 4. This is preferably a CCD camera. CCD cameras have the advantage that they are able to take a picture very precisely, are insensitive to el

REFERENCES:
patent: 2592039 (1952-04-01), Laetsch et al.
patent: 5220178 (1993-06-01), Dreiling et al.
patent: 5315367 (1994-05-01), Salvador et al.

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