Measuring and testing – Dynamometers – Responsive to force
Patent
1997-11-26
1999-06-29
Noori, Max H.
Measuring and testing
Dynamometers
Responsive to force
73800, G01L 510
Patent
active
059182873
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention concerns a measurement device for measurement of the tensile stress in an optical fiber or an equivalent wire, which measurement device is provided with a device for producing a vibration surge in the optical fiber, which vibration surge vibrates at a certain, pre-selected frequency and which advances as a linearly polarized wire wave, and with an optical location-sensitive indicator for measuring the advancing speed of the wire wave, and which measurement device is provided with an illuminator device for illuminating the optical fiber so that a shadow or an image of the vibrating fiber is cast onto the indicator, whereby the tensile stress of the optical fiber can be calculated from the equation T=v.sup.2 .multidot.M when the fiber mass per unit of length is known.
BACKGROUND OF THE INVENTION
An optical fiber is a thin glass fiber, whose diameter is about 150 micrometres. An optical fiber is used for replacing a copper conductor in telecommunications, because the data communication capacity of an optical fiber is much higher than that of a copper conductor. Furthermore, there is no shortage of the raw-material of the optical fiber, which is the case with copper.
Optical fiber is prepared in a so-called draw tower, which is a large tower with a height of about 8 to 9 metres, at whose top end molten glass is drawn downwards into a thin fiber. When the hot fiber travels downwards, it cools, whereafter, at the lower end of the tower, the fiber can be coated with a certain polymer in a particular coating vat. After coating, the fiber is transferred after a tension meter onto a particular roller, on which it is wound into a roll. It is known that bare fiber cannot be bent, because it breaks apart. After the polymer coating, the fiber endures bending very well. The draw rate of the fiber is at present about 4 to 10 metres per second and, among other things, the draw rate of the fiber and partly the thickness of the fiber are regulated by means of a tension meter. Currently, measurement of tension does, however, not take place until after the coating, because a bare fiber cannot be contacted. A tension measurement that takes place after the coating is, however, too late and provides an incorrect result concerning the tensile stress in a bare fiber. However, it would be desirable to increase the fiber draw rate, but in view of the process control, the tension of the bare fiber should be measured without contacting the fiber. The fiber tension meter that is used currently is a spring-loaded roller, over which a coated fiber advances. The magnitude of the loading indicates the fiber tension. There are some meters by whose means the tensile stress in a bare fiber can be measured by measuring the double refraction of light by directing light at the fiber and by measuring the magnitude of the double refraction. Such a meter is, however, highly complicated and expensive, and the phenomenon itself is weak. Therefore it has not gained popularity.
The object of the present invention is a novel acousto-optical meter, which measures the tension of a fiber by means of wire waves if the mass of the fiber per unit of length is known. By means of the meter it is possible to measure the tensile stress in the fiber without contacting the fiber and so that the advancing speed of the fiber is also compensated for. The principle is such that an advancing vibration is produced in the fiber, and the advancing speed v of said vibration is measured. If the mass of the fiber per unit of length is known (which is, as a rule, always the case), the tensile stress T in the fiber can be calculated from the simple formula:
Thus, in the meter, first a suitable advancing wire-wave surge must be produced in the bare fiber, and the advancing speed of said surge is measured in a certain way without contacting the fiber. In such a case, the tensile stress can be calculated from the formula mentioned above.
As regards the prior art, the above electro-optical meter may be mentioned, which measures the tensile st
REFERENCES:
patent: 4628747 (1986-12-01), Weitz et al.
patent: 4833928 (1989-05-01), Luukkala et al.
patent: 4914960 (1990-04-01), Kordahi
patent: 5228893 (1993-07-01), Smithgall
patent: 5359904 (1994-11-01), Luukkala et al.
Luukkala Mauri
Rajkkonen Heikki
Noori Max H.
Soundek Oy
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