Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-02-09
1991-07-09
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356429, G01N 2186
Patent
active
050308416
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for measuring the twist of a running, elongate test body, such as, for example, of a yarn or of a wire rope, by optical scanning of its surface and analysis of the scanning signal obtained in this case.
In a process of this type which is known from DE-A-3,628,654, a thread is grazingly acted upon by light, and specifically in such a manner that a part of the light beam is shaded off by thread and the part permitted to pass by the thread impinges on a light receiver. As a result of this, it is possible to detect certain structural alterations which are a measure of the thread period. Since this process, in which the profile is scanned to a certain extent, can be employed only when a detectable profile is present at all, this process is not suitable for the measurement of the twist of yarns.
A process of the initially mentioned type for the measurement of the twist of yarns is to be indicated by the invention.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in that the test body is illuminated by at least one light source and the light reflected by the test body is imaged onto a diaphragm and is measured by at least one photoelectric receiver, the output signal of which is investigated for periodicities caused by irregularities included in the test body, and in that the twist is derived from the wavelength or from the frequency of these periodicities.
Thus, the invention proceeds from the novel finding that the twist of yarns and the like leads to the bindingin of irregularities, which occur periodically on account of the twist. If the surface of a continuous test body is investigated for such periodicities, then the twist can be determined from these; this would not be possible by a simple scanning of the yarn profile.
The invention further relates to a device for carrying out the process according to the invention. This device is characterized by at least one light source for illuminating the test body, a diaphragm, an optical system for imaging the light reflected by the test body onto this diaphragm, at least one photoelectric receiver disposed in the beam path downstream of the diaphragm and an evaluation unit associated with this photoelectric receiver.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in greater detail herein below with reference to an illustrative embodiment in the drawings; in the drawings:
FIG. 1A shows a diagrammatic representation of a device according to the invention,
FIG 1B shows yet another preferred embodiment of the present invention, and
FIGS. 2,3 show diagrams for explaining the operation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1A shows a piece of a yarn G, which is conveyed by guide and transport means (not shown) in the direction of the arrow P through a device for measuring the yarn twist. As represented, this measuring device includes two light sources 1, 1' for illuminating the yarn G with a respective beam L, L', a diaphragm 2, onto which the beam R reflected by the yarn is imaged, a photoelectric receiver 3 disposed in the beam path downstream of the diaphragm and an evaluation unit 4 associated with this photoelectric receiver. Respective appropriate optical systems 5, 5' and 6 are provided in the beam path of the two beams L, L' and of the reflected beam R. A further lens 7 is situated between diaphragm 2 and photoelectric receiver 3. The light sources 1, ' are preferably formed by light-emitting diodes, so-called LEDs.
Before the measuring device is described in greater detail, the measurement process is to be explained now with reference to FIGS. 2 and 3: any yarn G exhibiting a twist or also any wire rope or any rope and the like exhibits, on account of the twist, certain irregularities with respect to its cross-section, and specifically, in particular, deviations from the cross-sectional shape. These characteristic deviations occur periodically, in which case the spacing between two successive such irregularities or, in other words,
REFERENCES:
patent: 3557377 (1971-01-01), Raasch
Nelms David C.
Zellweger Uster AG
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