Continuous measurement of yarn twist

Measuring and testing – Sheet – woven fabric or fiber – Filament

Patent

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Details

57264, 73651, G01H 1700

Patent

active

045848750

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a method and means for measuring the amount of twist in a travelling length of yarn and in particular to a non-destructive method for carrying out twist measurement.


BACKGROUND ART

Existing methods and means for measuring twist in yarn, for the most part, rely on the measurement of the twist angle alone and take no account of the important fact that the twist being measured is dependent upon the ever-varying yarn diameter. Such methods include a ply-twist method of measurement wherein a sample of yarn is untwisted in order to determine the twist that has been imparted to the yarn. Another method provides an untwist-twist technique wherein the yarn extends while being untwisted and contracts while being twisted in the opposite sense of its original twist so that when the original length of the yarn is attained during twisting in the opposite sense the total number of revolutions from untwist to twist is deemed to be twice the total twist of the length of yarn under test. Another method as shown in G.B. No. 1,266,450 proposes measurement of twist as the yarn is being formed at a point upstream of the twist spindle while the yarn is rotating.
The existing devices and methods use one of the following techniques:
(1) obtain a measurement of twist from two measured quantities--twist-angle and the yarn "diameter";
(2) obtain a measure of twist as the ratio of the specimen's tendency-to-rotate to the yarn speed necessitating the specimen to be actually in the process of twist insertion;
(3) use the twist-angle as a measure of the yarn twist ignoring the variation in the yarn "diameter".


DISCLOSURE OF INVENTION

The present invention proposes a method and means of measurement of twist in a rotating or non-rotating continuous travelling yarn which may be effected subsequent to the formation of the twisted yarn.
In one aspect the present invention provides a method of measuring twist in a translating yarn comprising sensing the frequency of vibration of a blade having an edge in contact with the translating yarn and calculating the twist of the yarn which is a function of the frequency of vibration of said blade.
In another aspect the present invention provides apparatus for measuring twist in a translating yarn comprising a blade adapted to have an edge in contact with a translating yarn, means for sensing the vibration imparted to said blade by the translation of said yarn across said edge, and means for measuring the frequency of said vibration.
This invention measures the twist in a translating yarn, whether it is rotating or not, continuously and non-destructively, by sensing the frequency of vibration of a blade which is in contact with the moving specimen, and amplifying, processing and displaying or printing the time-varying signal obtained therefrom.
The twist estimated by the new device and method is an accurate and precise measure of twist of a running yarn as will be appreciated by the facts:
(1) what is being sensed by the vibrating blade is the real twist itself;
(2) the measureand is independant of the yarn "diameter" variation; and
(3) only a single measurand is needed.


BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a schematic view of apparatus in accordance with a first embodiment of the present invention;
FIG. 2 is a schematic view of apparatus in accordance with a second embodiment of the present invention; and
FIG. 3 is a schematic view showing an example of how the apparatus of FIG. 1 or FIG. 2 can be used during the production of twisted yarn.


MODES FOR CARRYING OUT THE INVENTION

Referring to FIG. 1 which shows a vibration sensing blade 1 with its edge 1' placed so as to remain in contact with moving yarn 2. Blade 1 vibrates as yarn 2 moves across edge 1'; such vibration depends upon blade design and dimensions, yarn tension, speed and surface properties but mainly the surface twist angle .alpha.. By turning blade 1 around its

REFERENCES:
patent: 3273380 (1966-09-01), Seney
patent: 3613347 (1971-10-01), Carruthers
patent: 4133207 (1979-01-01), Weidmann et al.
patent: 4295360 (1981-10-01), Fountain
patent: 4330094 (1982-05-01), Mayer

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