A ceramic filled fluoropolymer composite coaxial cable insulation and the coaxial cable made therefrom is presented. In accordance with the present invention, the coaxial cable insulation is comprised of 60-25% fluoropolymer that is fibrillatable, 40-75% ceramic filler and a void content which is effective to provide a dielectric constant of approximately less than 2.30. In a preferred embodiment of the present invention, the coaxial cable insulative composite comprises approximately 40 weight percent PTFE, 60 weight percent fused amorphus silica and a void volume percent of between 30 and 60. Also in certain preferred embodiemnts, the composite may include 1-4% by weight of microfiberglass filler and the ceramic filler may be coated with a silane coating. The provision of the void volume is an important feature of the present invention and acts to substantially lower the overall dielectric constant of the insulative composite. Still another important feature of this invention is the provision of an effective amount of ceramic filler (silica) so as to reduce the coefficient of thermal expansion (CTE) to a CTE approximating that of copper. This results in a coaxial cable having electrical properties which are more temperature stable than the prior art; and coaxial cable assemblies having improved thermomechanical stability relative to the prior art.
A composite material is presented comprised of a ceramic filled fluoropolymer wherein the ceramic is coated with a fluorosilane and the ceramic has a volume % fraction of between about 45-50.
A coaxial cable (10) is for use in a power distribution network (N). The cable connects a surge protective device (SPD) in parallel with feeder lines (W1, W2) of the network. The SPD senses voltage surges on the feeder lines and clamps the voltages to a level at which loads (LD) connected downstream of the SPD are protected from excessive voltage levels. An inner conductor (12) and an outer conductor (14) have a dielectric material (16) separating them. The inner conductor is a round conductor, and the outer conductor forms a hollow cylinder in which the inner conductor and insulation material fit. A ratio of the inner diameter (D) of the outer conductor to the diameter (d) of the inner conductor is approximately 1.05. Thus, the diameter of the inner conductor is relatively large compared with the inner diameter of the outer conductor. A relatively large diameter of the inner conductor serves to minimize the dc resistance of the cable. Also, the dielectric material has a permittivity in the range of 2.0-4.0. Performance characteristics of the coaxial cable are compared with those of other conductors to illustrate the superiority of the coaxial cable in reducing "let through" voltage otherwise passed by a surge protector device to the loads.
The invention relates to a coaxial cable as well as to the manufacture of such a cable. The cable has a central conductor and an outer conductor which are separated from each other by an electrically insulating layer the outer conductor being provided, if necessary, with at least a protective coating. In accordance with the invention, the outer conductor of the cable has an electroconductive lacquer layer. In accordance with a preferred embodiment, a metal layer is applied to the lacquer layer. The cables in accordance with the invention can be manufactured much more rapidly than the known cables which have a stranded outer conductor or an outer conductor of metal foil. This advantage occurs in particular in the manufacture of very thin coaxial cables. In addition, the cables in accordance with the invention exhibit a satisfactory electromagnetic shielding.
Commercially available coaxial cables have been used successfully in single shot electromagnetic launcher and other pulsed power applications. The use of a coaxial cable interface between power source and pulsed power load reduces external magnetic fields and also aids in standardizing the interface, enhancing inter-changeability between a variety of power supplies and loads. As pulsed power systems continue to become more energetic and as the importance of repetitive operation increases, the use of commercially available cables becomes impractical because of the large number required for appropriate energy transfer. The cable according to the invention overcomes many problems encountered in the use of conventional cables. It incorporates a large area, flexible conductor in both the current feed and current return path, and matches these conductor cross-sections to provide uniform current paths. It also incorporates high temperature PFA TEFLON insulation capable of operating at 260 degrees C, and uses a high strength woven fiber cover to resist intense forces produced by internal currents and magnetic fields. A standardized, uniform dimension, nonarcing interface termination is also provided. The combination of components and materials easily allows this cable to be used to replace more than six conventional cables.
The present invention relates to a method for packaging an optical waveguide coupler where the coupler includes a body having two end portions and a constricted portion located between the end portions. The method includes placing the coupler in a mold where the mold surrounds at least the constricted portion of the coupler, introducing a polymeric composition into the mold so that the polymeric composition substantially fills the constricted portion, curing the polymeric composition, and removing the mold.
