Multi-conductor cable with transparent jacket

#The present invention is directed to an electrical cable having a helically wrapped transparent plastic jacket for wrapping a multi-conductor cable having a twisted pair conductor section and a flat parallel conductor section into a generally uniform round-shaped cable. The transparent jacket allows the flat parallel conductor section to be quickly identified for easier mass termination and attachment to a connector.

#Mass termination connectors have become more commercially popular because of the time and cost savings compared to the traditional method of stripping and individually terminating each conductor using a crimp terminal. These connectors are often used with a flat ribbon-type cable in which several conductors run parallel to one another and are spaced to match the spacing of the terminal elements of the connector. The use of a flat cable allows the ends to be quickly attached to a connector without having to strip and position each of the conductors individually, as with traditional round cables. However, while flat cables offer advantages with respect to ease of termination, they are more difficult to route than round cables because they are less flexible, and consequently are more prone to damage. In addition, they cause significant airflow restriction problems within high performance electronic systems cabinets.

#To overcome these disadvantages, cable manufacturers have taken standard flat cables with flat mass termination sections and manually folded them into a generally round-shaped cable, thus increasing the cable's flexibility and making it easier to route or lay the cable. In addition, cable manufacturers have usually manually covered this round-shaped cable with an additional covering such as nylon sleeving, or PVC tubing to protect the cable bundle. However, this method hinders the control of the cable's electrical properties because it is impossible with manual folding methods to predict how close the conductors are compressed together. A generally round-shaped cable has varying effective dielectric constants between the twisted pairs, due to the randomness of the manual folding and compression. This can cause wide variations in the cable's impedance and time delay, and consequently, increases the amount of reflection and crosstalk in the cable/connector system.

#FIG. 1 is a top view of a cable of the present invention showing its various sections;

#FIG. 2 is an end view of a flat section of the cable wrapped in a round jacket; and

#FIG. 3 is an end view of the flat section of the cable with the jacket removed.

#Referring now in detail to the drawings, FIG. 1 shows a multi-conductor cable 10 of the present invention, with various sections of the cable 10 exposed for clarity. The cable 10 has a transparent outer jacket 12 that wraps the cable 10 into a generally uniform round shape. A portion of the outer jacket 12 has been removed to show a first section with twisted pair conductors 14, and a second section with flat parallel conductors 16. Although the first 14 and second 16 sections of the cable 10 are shown in FIG. 1 without the outer jacket 12, this is done for illustrative purposes, and in use, the outer jacket 12 wraps the twisted pair conductors 14 into a generally uniform round shape. The uniform round shape increases the cable's flexibility allowing it to bend and be routed more easily, as well as achieve tightly controlled electrical performance.

#The cable 10 is comprised mostly of the twisted pair conductors 14 of the first section, with the flat parallel conductors 16 of the second section spaced at uniform or non-uniform intervals along the cable's length. Both sections are wrapped by the outer jacket 12, with the twisted pair section 14 being easily formed into the round shape, and the flat section 16, which comprises a series of conductors 18 spaced evenly apart in parallel fashion, folded over to form the round-shaped cable, as shown in FIG. 2. FIG. 2 shows a folded arrangement referred to as a zigzag fold. However, other fold arrangements may be used without departing from the invention so long as they result in a generally uniform round-shaped cable. In addition to being more easily formed into a round shape, the twisted pair section 14 reduces the crosstalk between the conductors 18 thereby enhancing the cable's electrical properties.

#The transparent outer jacket 12 facilitates the preparation of the cable 10 for attachment to a connector (not shown) by allowing the flat section 16 to be easily located through the transparent jacket 12. The jacket 12 is may be made of a single or multi-layer clear Mylar, polyester plastic or other transparent material that has a heat activated adhesive that bonds the layers of the jacket to one another, but not to the conductors 18 lying underneath. A double layer of polyester is used for mechanical protection as well as the need to keep the wrapped polyester from unraveling. A clear extruded jacket could also be used, but it is difficult to strip these jackets without damaging the insulated conductors underneath. Although the preferred embodiment of the jacket 12 shown in FIG. 2 is a double-layered clear plastic, it should be understood that variations of the jacket are contemplated to be within the scope of the invention. For example, a single layer transparent jacket made from a variety of material may be used without departing from the intended purpose or spirit of the invention.