Patent Application
20130269967
The present invention relates to data communication cabling pair separation. In particular, the present invention relates to a gas-encapsulated dual layer separator for a data communications cable.
Conventional data communications cables often include multiple twisted pairs within a protective outer jacket. Typical data cable constructions use pair separation fillers made from solid dielectric materials such as polyolefin and fluoropolymers to provide physical distance (i.e., separation) between the pairs within a cable, thereby reducing crosstalk. In the event a portion of the cable ignites, it is desirable to limit the amount of smoke produced as a result of the melting or burning of the non-conductive portions (e.g., separation filler) of the cable. It is also desirable to prevent or limit the spread of flames along the cable from one portion of the cable to another.
Turning to
One disadvantage to the use of separation fillers is that typical filler materials, such as fluoropolymers, have poor smoke- and flame-retardant properties. Therefore, the added material of the filler within the cable construction increases the amount of smoke that is emitted as well as the distance that flame travels along a burning cable. In order to mitigate those drawbacks, some manufacturers add flame retardants and smoke suppressants to the polyolefin and fluoropolymer materials used in the conventional fillers. However, smoke suppressants and flame retardants often increase the dielectric constant and dissipative factors of the filler, thereby adversely affecting the electrical properties of the cable construction by increasing the signal loss of the twisted pairs within close proximity to the filler.
As a result, some conventional manufacturers may “foam” the fillers in order to reduce the amount of material, where a foamed filler material is any material that is in a lightweight cellular form resulting from introduction of gas bubbles during manufacture. However, conventional foaming methods can only reduce the amount of material by no more than approximately thirty percent. Another drawback to foamed fillers is that during cable processing or manufacturing, crushing or deformation of the foamed fillers may occur resulting in compacted filler material and less separation between twisted pairs. As a result, foamed fillers often possess an undesirable imbalance between electrical and smoke/flame retardant properties.
Accordingly, in light of the above drawbacks associated with conventional fillers, separators, and cables, there is a need for a separator used in a data communications cable that reduces crosstalk between twisted pairs within the cable while simultaneously improving the flame spread and smoke emission properties of the cable.
Accordingly, the present invention provides an electrical cable assembly that includes a multilayer separator to encapsulate gas within a filler portion. The filler portion includes an inner member (e.g., a rigid inner layer cross bar frame) used to shape an outer layer that completely encapsulates gas within it.
Specifically, objects of the present invention are accomplished by a data communications cable that includes a plurality of twisted pairs of conductive wires and a separator between the plurality of twisted pairs of conductive wires. The separator includes an inner member and an outer layer being supported and shaped by the inner member for completely encapsulating at least one gas pocket between the outer layer and the inner member. The outer layer prevents the plurality of twisted pairs of conductive wires from entering the at least one gas pocket.
With those and other objects, advantages, and features of the invention that may become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the following detailed description of the invention, the appended claims, and the several drawings attached herein.
Several preferred embodiments of the invention are described for illustrative purposes, it being understood that the invention may be embodied in other forms not specifically shown in the drawings. It is an object of the invention to provide a cable assembly that reduces cross talk between pairs within data communications cables while simultaneously improving the flame spread and smoke emission properties of said cables. That may be accomplished by reducing the amount of filler material used in the data cable construction and replacing the filler with air, which has improved electrical properties.
As seen in
The separator 204 may be formed of melt processable materials, such as fluoropolymers, foamed or solid polyetherimides (PEI), polyetherimide-siloxane blends and copolymers, polyvinylchorides, polyolefins, polyethylenes, or the like. The separator 204 may also be formed at least in part by non-melt processable materials, such as PTFE, rubber, glass, silicone, or the like, by a combination of gas (e.g., air) and melt processable materials, such as is achieved with foaming. In one possible embodiment, the inner member 205 may be comprised of an olefin that is heavily loaded with a flame retardant and which has a higher dielectric constant and heat dissipation factor than an olefin that does not contain such additives. The outer layer 206 may be comprised of a thin layer of flouropolymer that has a much lower dielectric constant and dissipative factor than the inner member 205. That combination allows the cable 200 to have improved smoke- and flame-retardant properties as compared with single layer or solid fillers, such as filler 104 of cable 100, without degrading its electrical properties.
In the exemplary embodiment shown in
By encapsulating gas within the separator 204, the cable 200 reduces the amount of material used to separate the twisted pairs 102 as compared with conventional cable separators. It is appreciated that single gasses, such as nitrogen, or mixtures of two or more gasses, such as air, may be encapsulated within the separator 204 without departing from the scope of the subject matter described herein. Such gasses may be either inert or non-inert (i.e., reactive). They may also be used in foaming of the separator 204. By introducing the gas pockets 208 created by the outer layer 206 and the inner member 205, the cable 200 reduces crosstalk interference between the twisted pairs 102 while also improving the smoke/flame performance and the dielectric properties of the cable 200. The outer layer 206 preferably has a shape that pushes the twisted wire pairs 102 away from the cable's 200 center and away from each other to reduce interference between the wire pairs 102. For example, the outer layer 206 in combination with inner member 205 causes the wire pairs 102 to be positioned radially outwardly by about at least 0.003-0.010 inches more than if the outer layer 206 and gas pockets 208 were not employed. Moreover, the cable 200 achieves the desired pair-to-pair distance using less material than if the dual layer gas-encapsulated separator disclosed herein was not used. For example, the amount of filler material may be reduced by approximately 30-45% using the gas-encapsulated dual layer separator 204 of cable 200. Less material also makes the cable significantly less expensive to manufacture.
Another advantage of cable 200 is that gas that is encapsulated inside the outer layer 206 lowers the effective dielectric constant and, therefore, may reduce the signal loss of cable 200 as compared with cable 100.
Yet another advantage of the cable 200 is that the dual layer separator 204 may allow a manufacturer to optimize the flame and smoke retardant properties of the cable 200. For example, optimization of the layers (i.e., inner member 205 and outer layer 206) may allow the cable 200 to meet industry standards, such as the National Fire Protection Association (NFPA) 262 plenum test or the Underwriters Laboratories (UL) 1666 riser test for smoke/flame retardancy, while simultaneously maintaining the desirable electrical properties needed to meet requirements (e.g., insertion loss) for data communications cables.
The embodiment shown in
The primary segments 308 and 310 and the secondary segments 316-322 each include a terminal end which is remote from a junction point 324 of the segments. As mentioned above, the gas pockets 340 represent the reduction of material to sufficiently space the wire pairs 102 to reduce interference. The reduction in material reduces manufacturing costs and reduces the amount of combustible material, thereby improving the smoke and flame performance of the cable 200.
Although certain presently preferred embodiments of the disclosed invention have been specifically described herein, it will be apparent to those skilled in the art to which the invention pertains that variations and modifications of the various embodiments shown and described herein may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention be limited only to the extent required by the appended claims and the applicable rules of law.
| Number | Date | Country | |
|---|---|---|---|
| 61618274 | Mar 2012 | US |
