Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Optical fiber – waveguide – or preform
Patent
1998-03-24
1999-08-17
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Optical fiber, waveguide, or preform
264 129, 264 401, 425113, 425114, 425135, 4271632, B29D 1100
Patent
active
059389877
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for producing a basic element of a multi-element optical cable, in which method a tubular sheathing is extruded loosely around a fibre or a fibre bundle consisting of several optical fibres, the fibres are provided with the desired excess length with respect to the sheathing, and the unit formed by the sheathing and the fibres is pulled forward from the place following the point of extrusion to the next stage in the production line. The invention also relates to an arrangement for producing a basic element of a multi-element optical cable.
BACKGROUND
Such methods and arrangements are rather well known at present in connection with producing optical cables. Examples of known solutions include arrangements described in U.S. Pat. No. 4,893,998, German patent 3,425,649 and European patent application 0,286,819.
The disadvantages of the aforementioned arrangements include for example that the direction of travel of the unit formed by the fibres and the tubular sheathing changes rather rapidly after the extrusion head, since the unit is passed around a so-called locking wheel. In a production line equipped with a locking wheel the amount of the fibres is limited, since otherwise the fibres are positioned one upon another on the locking wheel, whereupon the outermost fibres may break at the worst. In order to operate reliably especially under conditions where the temperature fluctuates, for example an SZ stranded cable having a so-called minipipe structure requires great stability of each component of the cable and controlled interaction between the components. Examples of matters that cannot be realized in the best possible manner with the prior arrangements include the levelling of the variation in the length of the fibres situated inside the same protective pipe or sheathing, which is the most important factor in an SZ stranded multi-fibre structure, wherefore controlled levelling during the manufacture of the cable is important for the final result. The levelling of the variation in the fibre length is controlled by regulating the mutual tension of the fibres. Another example concerns the dimensions of the pipe or sheathing acting as a protective housing. A third example relates to the relaxation following the manufacture of an individual protective pipe or sheathing and the control of the relaxation during the manufacture. The stability must be absolute in an SZ stranded structure.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a method and an arrangement with which the drawbacks of the prior solutions can be eliminated. This is achieved with the method and arrangement according to the invention. The method according to the invention is characterized in that the tension of the fibres passed to the point of coating is maintained continuously at a controlled level, that the direction of travel of the fibres and the sheathing is kept straight before the pulling point and at the pulling point, and that the pulling point is placed from the coating point at a distance depending on the production rate of the production line. The arrangement according to the invention is in turn characterized in that the tension of the fibres passed to the coating tool is arranged to be kept continuously at a controlled level, that the direction of travel of the fibres and the sheathing is arranged to remain straight before the pulling device and at the pulling device, and that the pulling device is placed from the coating tool at a distance depending on the production rate of the production line.
The primary advantage of the invention is that it enables an increase of about 200 to 300% in the production compared to the results achieved with the prior arrangements. It must be noted that the aforementioned increase in the production is achieved without sacrificing the existing criteria for quality. The invention makes it possible to increase the production rate manyfold compared to the present rates of production by means of development and improved
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NK Cables OY
Vargot Mathieu D.
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