Patent Application
20160365176
Many conventional coaxial cables use braided copper wire to form a shield that isolates the cable from external electromagnetic radiation. The shielding also prevents leakage from the cable. The braided copper wire allows the cable to be flexible, but it also results in gaps in the shield layer that allow leakage and interference from external electromagnetic radiation. And, the inner dimension of the shield varies slightly because the braid cannot be flat. For better shield performance, some cables have a double-layer shield. This type of shielding may consist of two braids, but it is also common to have a thin metal foil shield covered by a copper wire braid. These shield designs often sacrifice flexibility for better performance and vice versa.
Additionally, these types of shieldings result in a cable with substantial weight. Heavier cables significantly increase transportation costs. For example, aircraft rely on many cables to carry a myriad of signals. Other forms of communication, such as radio frequency, simply cannot be used due to safety concerns. And, every pound of cable weight used on the aircraft increases the amount of fuel required to fly the aircraft. Similarly, heavier cables for ground use increase the fuel used by trucks to transport and lay the cable.
In one embodiment, a cable includes a conductive core and a dielectric material surrounding the conductive core along a length of the cable. The cable also includes a first shielding comprising braided tinned copper and a second shielding comprising aramid fibers having nickel physical vapor deposited thereon. The aramid fibers are braided about the first shielding to surround a majority of the first shielding along the length of the cable.
The figures and the description herein illustrate specific exemplary embodiments of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within the scope of the invention. Furthermore, any examples described herein are intended to aid in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the invention is not limited to the specific embodiments or examples described herein.
Prior to braiding, the aramid fibers are coated with Nickel using a “dry” physical vapor deposition process. This generally results in a 30 Ohm Nickel-aramid, 400 denier material. The fibers are then spun into yarns that are fed into the fabric braiding machine. Both shieldings 103 and 105 provide electromagnetic shielding for the cable 100. But, the Nickel aramid fiber shielding 103 improves shielding performance of the cable 100. And, as the aramid fibers are not metal, per se, they dramatically decrease the overall weight of the cable. In some embodiments, the braided Nickel-aramid shielding 103 provides a weight savings of approximately 30% in total cable weight when compared to traditional double metallic braided shieldings.
Shielding performance was found to be optimal when the aramid fiber shielding 103 surrounded at least 80% of the shielding 105. Part of the difficulty in implementing the shielding 103 regards the brittle nature of the Nickel that is physical vapor deposited on the shielding 103. That is, the Nickel tends to make the aramid fibers and subject to fracturing. When spun into yarn and braided to at least 80% coverage of the braided tinned copper shielding 105, fracturing of the aramid fibers was shown to be substantially less. And, performance of the electromagnetic shielding increased well beyond levels of traditional shieldings.
Typically, once the shieldings 103 and 105 are braided onto the cable 100, a jacket 104 surrounds the length of the cable 100 for protection of the underlying components. For example, the jacket 104 may be configured from a heat shrink material that is wrapped around the cable 100. When heat is applied to the cable 100, the jacket 104 hardens and protects the underlying components from external elements. The jacket 104 also compresses the shielding 103 against the shielding 105 to “squish” or otherwise flatten the fibers of the shielding 103 so that the Nickel thereon has fewer gaps, thereby increasing the shielding performance.
As mentioned, the Ni-Aramid fibers are configured by depositing the Nickel onto the aramid fibers through a dry physical vapor deposition process. In this regard, Nickel is deposited on the aramid fibers at an atomic level. And, the physical vapor deposition of the Nickel essentially plates Nickel onto the aramid substrate. However, other fibers may be used including carbon fibers, cellulose, and jute. Jute is a relatively long, soft, shiny vegetable fiber that can be spun into coarse, strong threads. In one embodiment, the layer of Ni coated fibers are braided into a strand count of about 12,000 (e.g., 4 toes at 3,000 strands per toe), although other strand counts may be used.
It should be noted that the invention is not intended to be limited to the exemplary embodiment as more braided Nickel-aramid fiber shieldings 103 can be used. For example,
Additionally, the invention is not intended to be limited to braided shieldings. In some embodiments, the shieldings may be served (i.e., wrapped) about the cable 100.
In contrast, when a single Nickel-aramid fiber shielding 103 is braided over a tinned copper braided shielding, shielding effectiveness increases dramatically.
And, equally important, the weight of the cable decreased. The samples of the traditional cables had a weight of about 7.1 grams per 12 inches with an extruded jacket, whereas the braided tinned copper shielding 105 with the braided Nickel-aramid fiber shielding 103 resulted in a weight of about 3.2 grams per 12 inches with a heat shrink jacket.
This patent application claims priority to, and thus the benefit of an earlier filing date from, U.S. Provisional Patent Application No. 62/175,814 (filed Jun. 15, 2015), the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62175814 | Jun 2015 | US |
