This application claims the benefit of U.S. Provisional Patent Application No. 61/450,351, filed Mar. 8, 2011, the disclosure of which is incorporated by reference herein in its entirety.
Cables are commonly used with electronic devices such as computers, cellphones, and portable media devices. When cables are subject to repeated physical manipulations that exert bend and strain forces on the cable, the cable can eventually break or tear. Smaller diameter cables and cables used in connection with portable electronic devices are generally more susceptible to breakage because they are more frequently handled by being bent, pulled, tangled, or wrapped. What is needed are cables that are better able to withstand use stresses so that the life expectancy of such cables is increased.
Cables with braided shields constructed from metal-doped fibers and methods for making the same are disclosed. These braided shields maintain the electrical conductivity of a conventional all-metal braided shield, but are less stiff. This allows for a much more flexible cable and increased cable flex life because the metal-doped fibers are not as sensitive to bending fatigue as their all metal counterparts.
The above and other aspects and advantages of the invention will become more apparent upon consideration of the following detailed description, taken in conjunction with accompanying drawings, in which like reference characters refer to like parts throughout, and in which:
Cables constructed according to embodiments of this invention incorporate a high strength, low fatigue braided shield constructed from metal-doped fibers. This braided shield maintains the electrical conductivity of a conventional all-metal braided shield, but is less stiff. This allows for a much more flexible cable and increased cable flex life because the metal-doped fibers are not as sensitive to bending fatigue as their all metal counterparts.
Cable 100 can include conductor bundle 110, electromagnetic interference (“EMI”) shield 120, braided shield 130, and jacket 140. Conductor bundle 110 can form the core of cable 100 and includes one or more conductors for conveying signals and/or power. The number of conductors included in conductor bundle 110 depends on the desired function of cable 100.
EMI shield 120 surrounds conductor bundle 110 to provide electromagnetic shielding. EMI shield 120 can be constructed from aluminum, mylar, aluminized mylar, or other suitable material. EMI shielding 120 can be bound to conductor bundle 110 with a binding agent (not shown).
Braided shield 120 surrounds EMI shield 120 and conductor bundle 110. Braided shield 120 can provide grounding for cable 110 and/or additional electromagnetic shielding. Braided shield 120 can be constructed from fibers that are coated with a conductive metal. The fibers can be synthetic or natural fibers. Synthetic fibers can include, for example, polymer fibers such as polyester, vinyl ester, nylon, Kevlar, or fiberglass. Another example of a synthetic fiber is carbon fiber, which can be reinforced with a polymer. Examples of natural fibers can include cotton or hemp.
The fibers can be coated with any suitable conductive metal such as silver, gold, nickel, aluminum, zinc, brass, bronze, iron, steel, platinum, any combination thereof or alloys thereof. The fibers may be dip or spray coated with metal. A specific example of a metal-doped fiber is a silver coated Kevlar fiber. Another specific example is a nickel coated carbon fiber.
Braided shield 130 can be braided directly onto EMI shield 130 according to any suitable braided pattern. The metal-doped fibers can be woven together around EMI shield 130 to form a weave of such fibers. The weave may comprise the same metal-doped fiber or a combination of different metal-doped fibers. The density of the weave may vary; however, it may be desirable to minimize interstitial spacing. In some embodiments, braided shield 130 can be weaved with a density sufficient to perform the same electromagnetic shielding function of EMI shield 120. In such an embodiment, EMI shield 120 can be eliminated.
In another embodiment, braided shield 130 can be woven as a separate component that is slid over conductor bundle 110 and EMI shield 120.
Some fibers have a tensile strength that is higher than a metal counterpart (e.g., copper). In other words, such fibers have a greater modulus of elasticity or greater capacity for plastic deformation than certain metal counterparts. Such fibers can also have a smaller cross-section than the metal counterpart, thereby resulting in a smaller braided shield cross-section. This in turn enables cable 100 to have a smaller cross-section.
Jacket 140 encapsulates braided shield 130, EMI shield 120, and conductor bundle 110 to form the outermost layer of cable 100. Jacket 140 can be any suitable material such as, for example, a thermoplastic, silicon, or urethane. Jacket 140 can bond braided shield 130 to EMI shield 120 so that it becomes permanently integrated into cable 100.
At step 220, a plurality of metal-doped fibers are braided directly onto the conductor bundle so that the metal doped fibers form a braided shield. The braided shield can have any suitable pattern and can include fibers of the same type or multiple different types. The density of the pattern can depend on several factors, including the speed at which the conductor bundle is fed through the braiding the machine, the number of fibers being braided onto the bundle, and the weave pattern.
At step 230, the conductor bundle and braided shield are encapsulated with a jacket to permanently bond the metal doped fibers to the conductor. It is understood that additional steps may be added without departing from the spirit of the invention. For example, a step may be inserted in between steps 210 and 220 to encapsulate the conductor bundle with an electromagnetic interference shield.
The described embodiments of the invention are presented for the purpose of illustration and not of limitation.
Number | Date | Country | |
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61450351 | Mar 2011 | US |