Serrated cable core

Details Serrated cable core Serrated cable core

2002-06-21

2004-11-09

Mayo, III, William H. (Department: 2831)

Electricity: conductors and insulators

Conduits, cables or conductors

Insulated

C174S1020SP, C174S103000, C174S109000

Reexamination Certificate

active

06815617

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This disclosure relates to the field of cables. In particular to coaxial and triaxial cables for use with automatic stripping equipment.
2. Description of the Related Art
In the modern world, cables are everywhere. They are used to transmit numerous signals between individual electronic components which can range from the very basic building blocks of electrical systems to the most cutting-edge consumer and commercial devices. One of the most common of these is the coaxial cable which can be used for everything from connecting a DVD player to a TV, to connecting sophisticated medical apparatus to processing computers, to hooking up components of computer or telecommunications networks.
As the coaxial cable (and the related triaxial cable) have come into increased use in both consumer and commercial contexts, the need for more and more finished cable assemblies to be produced has become greater. While cable can be manufactured on large rolls using modern assembly techniques, for many applications the cable needs to have terminators attached to the ends and/or be otherwise “finished” so it can connect to the devices which are to be interconnected by the cable in a simple, repeatable, and understandable fashion. Finished cable manufacturers/assemblers therefore process the rolls of raw cable into the 3′, 10′, 100′ or other desired length “cables” that most people are familiar with. The terminators for attachment to these cables come in a wide variety of forms, and the resultant cables are also generally produced in a wide variety of sizes and intended for a wide variety of applications. Just going down to any electronics store will present a consumer with a dizzying variety of finished cables and most electronics stores will stock hundreds if not thousands of feet of finished cables. Some will even stock raw cable and will provide a particular finished length upon demand by a consumer.
In addition to the retail consumer, businesses generally need significant quantities of cable to setup and maintain computer networks and other internal electrical systems. Some businesses even rely on cables as an essential part of doing business. For instance, television news organizations generally need cables in conjunction with their cameras to perform their duties. All these cables are generally finished to allow for easy connection and disconnection of the electronics. Even when cables are permanently attached to devices, electronics equipment manufacturers need to be able to prepare raw cable to be attached to those products (essentially making the product the cable terminator). There is therefore an increasing demand for cable to be cut to a desired length and prepared for attachment to a terminator whether for finished cable construction or direct attachment to an end product.
To help in understanding how a cable is prepared for this attachment, a coaxial cable cross section should be visualized. The cable consists of a series of concentric cylinders or cylindrical tubes each surrounding the previous. The tubes are arranged so that there are alternating conductor and insulator layers. Two of each in a coaxial cable, while a triaxial cable simply adds one additional conductor and insulator outside the coaxial to form additional concentric layers. Larger axial cables may add additional alternating layers. To connect raw axial-style cable to terminators is conceptually fairly simple. Each of the internal conductors needs to be attached to an appropriate position on the terminator so that when the terminator is attached to a source, the appropriate signal is sent down the cable.
Because of the axial design of these cables, the conductors are generally insulated from external exposure (an insulator is the outermost layer) down their entire length (longitudinal dimension). Connecting to the extreme ends of the cylinder can be difficult, so generally a portion of the outermost tubes of the cables are stripped off the ends of the cable for a predetermined longitudinal distance from the end of the cable. This increases the surface area of the conductors available for each connection by allowing access to some of their longitudinal surface area. These stripped portions are then used to connect to the terminator resulting in good electrical connection between the cable and the terminator.
Because of the axial arrangement of the conductors and insulators, stripping a coaxial or triaxial cable generally involves a cutting tool cutting into the cable to a particular depth at a set distance from the cable end, and then the portions of the cable above this depth being “stripped” away by being pulled off the end of the portions that are to remain. This may be repeated at multiple different longitudinal distances and depths to get the desired exposure of all the various conductors present in the cable.
When making cables that are incorporated into devices which are mass produced, or when mass producing finished cables for the market, the above procedures are often accomplished by specialized machines that cut and strip the cables at great speeds to prepare them for attachment. One such machine is the PowerStrip 9500 RS Automatic cut and strip machine manufactured by Schleuniger and available commercially. These stripping machines, however, need to be able to strip the wire in a consistent and repeatable manner so that the cable is correctly stripped in preparation for the terminator attachment. This requires the stripping machine to be able to exert a particular force which is great enough to fully separate and strip off the undesired portions of the cable, but is not sufficient to damage the portions of the cable which are not to be removed.
With the advent of these machines, it was discovered that for the machine to be able to effectively remove the inner layer(s) (particularly the innermost insulator, often called the insulation, from the innermost conductor), such force was required on the pull step that the inner conductor(s) and inner insulator(s) (the cable core) would be pulled from within the cable, rendering the cable non-functional.
To combat this problem, multiple ideas have been proposed. These include increasing the contact force between the shield and the core by using tighter jackets to compress the shield, by using more rigid jackets, by using less rigid insulators, or heating the shield and insulators to get a better adhesion with at least some of the conductors. The problem with these methods is that they often do not solve the underlying issue of the stripping machine damaging the cable while attempting to strip it, and may add unnecessary cost. Tighter jackets or heat generated bonds often result in too much resistance between the components causing the stripping machine to fail to strip the cable and instead only partially separating the layers creating an unusable portion. Less rigid insulators help with the stripping problem by allowing the shield to cut into the insulator, but the result is a less rigid cable than is desired for many applications. Rigid jackets can also help with the stripping problem, but the resultant cable is more rigid than is desirable for many applications.
BRIEF SUMMARY OF THE INVENTION
Because of these and other previously unknown problems in the art, disclosed herein is an axial cable, such as, but not limited to, a coaxial, triaxial, twinaxial, or armored cable, which includes at least one serration on an insulative or conductive layer internal thereto. These serrations may appear on insulators or inner jacket layers and are in physical contact with conductive layers such as shields which axially surround the insulative layers. The serrations generally increase the contact force between the insulative layers and the conductive layers to help prevent separation of the cable core during stripping of the axial cable. Methods of manufacturing such cables are also disclosed.
Described herein, among other things, is an axially arranged cable comprising: an insulator having an outer surface

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