Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Utilizing plasma – electric – electromagnetic – particulate – or...
Patent
1992-12-23
1994-06-14
Thurlow, Jeffery
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Utilizing plasma, electric, electromagnetic, particulate, or...
156172, 15624412, 15624414, 264103, 264108, 264173, 264174, 264230, 264DIG71, B29C 4702
Patent
active
053207882
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process for producing a plastic casing reinforced against tensile forces by, elements for resisting extension in the plastic casing. The process includes the elements being extruded in molten form at the same time as the plastic casing serving to receive these elements is extruded.
In many cases in which plastic is used as a casing or walling material, the strength value of most plastics does not satisfy the demands made on the casing. Therefore, it is known, for example for plastic insulations for electrical and/or optical cables or lines, to incorporate in the insulation or to bond in a suitable form with the insulation elements for resisting extension (German Patent 2,740,162, German Patent 2,818,297). In such cases, the elements for resisting extension have been placed on or under the insulation and, for example, are adhesively bonded with the insulation, jacket or casing. Processes are also known in which the elements for resisting extension have been fed to the insulation during extrusion.
JP-A-62,130,821 discloses a process in which a tubular body is extruded, reinforcing filaments which may consist, for example, of LCPs and are also embedded in the tube walling being extruded in coextrusion by means of tubular dies. These reinforcing filaments run in straight lines, which may be disadvantageous for some applications, for example in the case of strong bending stresses, in the case of stranding operations, etc.
Also to be cited in this connection as prior art are U.S. Pat. Nos. 4,553,815 and 4,767,183, in which although the use of LCPs reinforcing against tensile forces is already described in the case of optical cables, their simultaneous extrusion is not.
SUMMARY OF THE INVENTION
The invention is based on the object of providing a jacket, casing or covering which is particularly suitable for optical glass fibers and can be used universally. The way in which this object is achieved according to the invention in the case of a process of the type mentioned at the beginning is that the plastic casing serves for producing coverings for optical glass fibers or cables and that, after extrusion, the plastic casing is subjected to a torsional operation before or during the winding-up process, in such a way that the elements for resisting extension run spirally.
In this way, the elements for resisting extension distribute themselves helically, seen in the longitudinal direction, about the longitudinal axis of the covering and, as a result, the latter can optimally withstand, for example, bending and/or stranding operations. Consequently, an optimum protection of the sensitive optical waveguides against mechanical stresses is ensured. The casing and the elements for resisting extension are produced in the desired arrangement from one extrusion apparatus in one process. To be regarded as the special feature in any event is that the reinforcing filaments are incorporated in the desired form in the plastic casing in the molten state of the matrix. Consequently, the primary casing thus produced already fulfills a reinforcing function, which in some cases allows dispensing with additional or further reinforcing elements (Kevlar, GRP, wire reinforcement). This form of reinforcement also allows tough or flexible plastics having good bending properties in a broad temperature range to be used for the primary casings.
In a development of the invention, an embodiment is preferred in which the elements for resisting extension consist of polymers based on liquid crystal polymers (LCPs). This achieves the effect that the elements for resisting extension can be extruded particularly simply in molten form at the same time as the plastic casing or profile serving to receive these elements.
The torsional operation can be accomplished by using stranding devices, in particular based on SZ-stranding devices. In the case of a stationary extrusion die, the extrudate is twisted by making the take-off and the wind-up rotate and thus obtaining a helical fiber reinforcement, or
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Niesemeyer Norbert
Reissenweber Wilfried
Schneider Reiner
Siemens Aktiengesellschaft
Thurlow Jeffery
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