Patent Application
20210057129
The present invention relates generally to coaxial cables. More particularly, the present invention relates to a coaxial cable with two hour circuit integrity.
Known coaxial cables used in antenna systems and other radio frequency applications are not constructed to meet existing circuit integrity fire test requirements, such as UL 2196 and UL 263, while maintaining sufficient transmission capability. Instead, to keep a circuit functioning for two hours as required by the circuit integrity fire test requirements, known coaxial cables employ flame and heat barriers inside of an outer conductor of the coaxial cables or in conjunction with a solid insulation system. However, these known cable designs have a reduced throughput and/or choke signals traveling therethrough when compared to similar coaxial cables without such flame and heat barriers.
In view of the above, there is a need and an opportunity for improved coaxial cables.
While this invention is susceptible of an embodiment in many different forms, specific embodiments thereof will be described herein in detail with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention. It is not intended to limit the invention to the specific illustrated embodiments.
Circuit integrity fire test requirements, such as UL 2196 and UL 263, require that a cable maintain operation for up to two hours in the presence of a catastrophic fire event. Accordingly, embodiments disclosed herein can include a coaxial cable with two hour circuit integrity and a method for manufacturing the coaxial cable. In some embodiments, the coaxial cable disclosed herein can be used to maintain a connection between emergency first responders and a home base of the emergency first responders.
In some embodiments, the coaxial cable disclosed herein can include an inner conductor, an outer conductor, an insulating layer disposed between the inner conductor and the outer conductor that includes a polymer support structure and air pockets that act as a dielectric for a signal transmitted through the inner conductor, an outer jacket, and a flame barrier disposed between the outer jacket and the outer conductor to avoid choking the signal. Furthermore, in some embodiments, the flame barrier can prevent fire from advancing from the outer jacket to the outer conductor for at least two hours.
In some embodiments, the polymer support structure can be deployed in a star configuration having four prongs, and in these embodiments, the air pockets can surround at least a portion of the star configuration. However, it is to be understood that other configurations of the polymer support structure that allow for airflow, for example, by being surrounded, at least in part, by the air pockets, are contemplated. For example, embodiments of the polymer support structure with more than four prongs and less than four prongs are contemplated.
Various embodiments of different materials are contemplated for the flame barrier and the center conductor. For example, in some embodiments, the flame barrier can include mineral filled silicone, and in some embodiments, the center conductor can include copper clad steel or copper clad aluminum.
In some embodiments, a dielectric constant of the flame barrier can be higher than a dielectric constant of the polymer support structure and a dielectric constant of the air pockets. In these embodiments, if the flame barrier were disposed inside of the outer conductor, then the flame barrier would choke the signal.
In some embodiments, the coaxial cable can include a first heat barrier disposed between the flame barrier and the outer conductor and a second heat barrier disposed between the first heat barrier and the flame barrier. In such embodiments, the first heat barrier and the second heat barrier can work with the flame barrier to prevent the fire from advancing from the outer jacket to the outer conductor. In some embodiments, the first heat barrier can include mica tape, and the second heat barrier can include PTFE tape. However, in some embodiments, the first heat barrier can include PTFE tape, and the second heat barrier can include mica tape.
In some embodiments, the outer jacket 27 can be approximately 0.03 inches thick with an outside diameter of approximately 0.805 inches, the flame barrier 32 can be approximately 0.08 inches thick with an outside diameter of approximately 0.745 inches, the first heat barrier 34 can be approximately 0.01 inches thick with an outside diameter of approximately 0.585 inches, the second heat barrier 36 can be approximately 0.01 inches thick with an outside diameter of approximately 0.565 inches, the outer conductor 24 can be approximately 0.034 inches thick with an outside diameter of approximately 0.545 inches, the insulating layer 26 can be approximately 0.144 inches thick with an outside diameter of approximately 0.477 inches, and/or the inner conductor 22 can be approximately 0.189 inches thick and have an outside diameter of equal value.
Although a few embodiments have been described in detail above, other modifications are possible. For example, the logic flows described above do not require the particular order described or sequential order to achieve desirable results. Other steps may be provided, steps may be eliminated from the described flows, and other components may be added to or removed from the described systems. Other embodiments may be within the scope of the invention.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific system or method described herein is intended or should be inferred. It is, of course, intended to cover all such modifications as fall within the spirit and scope of the invention.
