Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Optical fiber – waveguide – or preform
Patent
1995-10-13
1997-10-14
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Optical fiber, waveguide, or preform
264 129, 264568, 2642102, 425114, 4253261, B29D 1100
Patent
active
056768923
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a method as well as an installation for the manufacture of an optical fiber cable.
BACKGROUND OF THE INVENTION
Known optical fiber cables include a bundle of fibers assembled together in the form of layers, of already cabled fibers or of strips which are surrounded by a first outer tube of rigid or flexible structure formed by extrusion of a synthetic material.
In certain applications, optical fibers are housed in a loose manner on the interior of the tube and a viscous material such as a protection grease known under the British name "jelly" is injected into the interior of the tube in order to embed said fibers in the latter.
The manufacture of this type of cable is brought about in a manner such that the fibers on the interior of the tube exhibit relative thereto a selected excessive length obtained by the influence and the combination of different parameters throughout the entire manufacturing chain.
In the known methods and installations presently used, the optical fibers are unwound from a pay-out device including a feed reel freely mounted in rotation on an axle, the tension of the unwound fiber being controlled so as to remain constant.
Such fiber is thereafter drawn down through an extrusion head in which synthetic material at a high temperature in a viscous form is supplied around said fibers in order to form the protection tube hereinbefore mentioned in a manner coaxial to and on the exterior of the fibers.
At this point, the grease or "jelly" is injected in order to fill the tube and for coating the optical fibers in the latter.
After this extrusion step, the plastic tube is cooled in a first cooling receiver and is urged in traction in being wound around a first draw-in reel. The method is continued by the passage of the tube through another cooling receiver and through another draw-in reel with a control of the tractions on such tube through the use of strain gauges.
Such method and installation give satisfaction but solely up to a limit diameter of the tube and up to a limited number of fibers on the interior of the tube. Effectively, and in particular, beyond a tube diameter of 6 mm, the appearance of defects is ascertained in the outer form of the tube, but also in the excess length of the fibers as well as in the aspect of its outer surface. Is is thus very difficult to obtain a tube exhibiting a smooth outer surface and the excessive length also becomes difficult to control.
SUMMARY OF THE INVENTION
An object, the present invention is to provide a method and an installation for the manufacture of an optical fiber cable enabling the overcoming of such drawbacks and thanks to which the smooth aspect and the circular form of the tube surrounding the fibers can be controlled, whatever be the number of fibers on the interior of the latter,whilst moreover enabling a sufficient control of the excess length on such fibers.
A object of the invention is to provide a method of manufacture of an optical fiber cable including a tube in which said fibers are housed, characterized in that it includes the following steps in which:
a) optical fibers are brought from one or several pay-out devices,
b) such fibers are introduced into the interior of an extrusion head supplying a sheathing material in viscous form extruded from said head around the fibers,
c) at the output of the extrusion head, the sheathing material is directly preformed so as to cause it to take its definitive geometric form corresponding to that of the solid tube before and while it envelops said fibers,
d) the cable made up from the tube and fibers is rolled up around a first drawn-in reel, then
e) the cable is cooled in order next to cause it to pass through a second draw-in reel, while maintaining constant the tension between the two draw-in reels.
A further object of the invention is provided an installation for the manufacture of an optical fiber cable comprising:
pay-out means capable of supplying optical fibers, for example under the form of ribbon, and
extrusion means
REFERENCES:
patent: 4154783 (1979-05-01), Jackson
patent: 4728470 (1988-03-01), Einsle et al.
patent: 4772435 (1988-09-01), Schlaeppi et al.
patent: 4814116 (1989-03-01), Oestreich et al.
patent: 4861525 (1989-08-01), Oestreich
E. Kertscher S.A.
Vargot Mathieu D.
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