Optical waveguides – Optical transmission cable
Reexamination Certificate
1998-06-22
2001-02-13
Ullah, Akm E. (Department: 2874)
Optical waveguides
Optical transmission cable
Reexamination Certificate
active
06188821
ABSTRACT:
The present invention relates to apparatuses and methods for making self-supporting type fiber optic cables.
Fiber optic cables include optical fibers which transmit information in, for example, cable television, computer, and telephone systems. Self-supporting type fiber optic cables are designed for aerial self-supporting applications and typically include a messenger wire and a core section having conductors therein which may be optical fibers, or a combination of optical fibers and electrical wires. Self-supporting fiber optic cables of the “figure 8” type may be characterized into two general categories, namely, self-supporting cables with a core section having no excess length relative to the messenger wire, and self-supporting cables having a core section having an overlength, typically about 0.2%, relative to the messenger wire. Examples of known self-supporting cables having no core section overlength are disclosed in U.S. Pat. Nos. 4,449,012, 4,763,983, 5,095,176, and 5,371,823, the respective disclosures of which are incorporated by reference herein. Examples of known self-supporting cables having a core section overlength are disclosed in U.S. Pat. Nos. 4,662,712 and 4,883,671, the respective disclosures of which are incorporated by reference herein.
When installed in a self-supporting application, self-supporting cables may experience a high degree of tension. The messenger wire bears most of the tension, thereby supporting the core section, and protecting the optical fibers in the core section from high tensile forces. As tension acts on the messenger wire, however, the messenger wire tends to elongate which results in an elongation of the core section. Elongation of the core section of a self-supporting fiber optic cable not having a core section overlength may cause attenuation losses in the optical fibers in the core section. On the other hand, where the core section of a self-supporting cable having a core section overlength is elongated, the elongation is, up to the amount of existing overlength of the core section, advantageously taken up by the overlength in the core section whereby the core section may be elongated without potentially causing attenuation in the optical fibers.
Several methods of manufacturing self-supporting fiber optic cables having a core section overlength have been developed, for example, a sag formation method and a thermal/tensioning method. In the sag formation method, for example, as is disclosed in JP-8-136778 and JP-8-211260, the core section is given an excess length in the form of sagged portions and then the messenger and the core section are bound together at spaced intervals by a wire. As an alternative to wire, plastic clamps may be extruded about the messenger and the core section, for example, as is disclosed in JP-61-29811, U.S. Pat. Nos. 4,883,671, and 4,662,712. In lieu of a wire or clamps, a jacket may be simultaneously extruded about the messenger wire and the core section thereby forming a web between the messenger wire and the core section, for example, as is disclosed in JP-9-43467. In the event a jacket is extruded about the messenger and the core section, the extruder may include a plunger for forming windows in the web, as is disclosed in JP-46-38748 and JP-8-75969.
An example of the thermal/tensioning method is disclosed in JP-9-54232. The core section overlength is created by a heater disposed between a capstan and a brake. The heater heats the messenger wire and causes it to thermally elongate while the capstan and the brake simultaneously apply tension to the messenger wire to mechanically elongate the wire. The elongation created in the messenger wire is therefore the sum of the incremental elongations made by the thermal and mechanical elongations of the messenger wire.
Several disadvantages inhere in the use of the thermal tensioning method. First, heating the messenger wire is expensive and limits the production speed of the manufacturing line. Cooling of the messenger wire occurs at a relay drum around which the messenger wire is wrapped prior to extrusion of a jacket, and cooling of the messenger wire also occurs in a cooling trough. As the messenger wire cools its length shrinks thereby creating excess core length which may result in undesirable adhesion of the core to the messenger. Moreover, the capstan frictionally engages both the messenger wire and the core section which may result in a damaging amount of tension being applied across the webs that connect the messenger wire and the core section. Furthermore, the cable fits in the capstan in a way that does not allow for a range of core section diameters to be used with the capstan.
An additional disadvantage is that there is a lack of clearance space between the core section and the capstan. As the self-supporting cable progresses through the capstan, the tension in the cable is released thereby causing the core section to undulate. Since the cable receiving profile in the capstan is sized so that the jacketed messenger wire and core section are both coupled to the capstan, no clearance space exists for the formation of the undulations in the core section. The undulations therefore are defined by a warping of the core section exteriorly of the capstan. The lack of clearance space causes friction between the cable and the capstan that may result in deformation of the cable, and/or tearing of the webs, and the final product may not, therefore, meet customer specifications.
OBJECTS OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a method of making a fiber optic cable having a messenger wire and a core, the method including the steps of: drawing the messenger wire and the core through a cable manufacturing line; extruding a jacket about the messenger wire and core thereby defining a cable with a messenger section and a core section; passing the cable across a tensioning apparatus having a clearance section receiving the core section; relieving tension in the cable as the cable progresses through the tensioning apparatus; and forming undulations in the core section as the cable progresses through the tensioning apparatus by maintaining an essentially decoupled relationship between the core section of the cable and the clearance section of the tensioning apparatus. The method may include a step wherein the tensioning apparatus cuts windows between the messenger section and the core section.
It is another object of the present invention to provide a method of making a fiber optic cable having a messenger wire and a core, the method including the steps of: applying tension to the cable and drawing the messenger wire and the core through a cable manufacturing line; passing the fiber optic cable across a tensioning apparatus; and dissipating the tension in the messenger wire only during progression of the cable through the tensioning apparatus.
It is a further object of the present invention to provide a cable tensioning apparatus for making a self-supporting fiber optic cable having a messenger section and a core section, the apparatus including: a messenger tensioner having a profile with a tensioning recess and a clearance recess; the tensioning recess being operative to grip and to apply tension to the messenger section; and the clearance recess being operative to essentially frictionlessly accommodate the formation of undulations in the core section. The tensioning apparatus may include at least one knife for forming windows in the cable.
It is another object of the present invention to provide an apparatus for manufacturing a fiber optic cable, the apparatus including: a cable core tensioning apparatus; a messenger wire tensioning apparatus; and a cable tensioning apparatus, the cable tensioning apparatus including a messenger tensioner having a profile with a tensioning recess and a clearance recess, the tensioning recess being operative to apply tension to a messenger section of the cable, and the clearance recess being operative to essentially frictionlessly accommodate the formation of undulations
McAlpine Warren W.
Sigmon Mark A.
Aberle Timothy J.
Siecor Operations LLC
Ullah Akm E.
LandOfFree
Apparatuses and methods for use in the making of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatuses and methods for use in the making of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatuses and methods for use in the making of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2613009