Patent Application
20150136443
The present disclosure is directed to electrical transmission cables.
As used herein, the term “wire” will refer to a single, individual electrical conductor and the insulation covering that conductor. The term “cable” will refer to a collection or group of at least two wires whose insulation layers are initially joined in some manner. In the past insulated transmission cables were designed with multiple insulated wires, each of which had insulation layers that defined a generally rectangular cross-section. The individual wires were separated by V-shaped notches.
In one aspect, the present disclosure concerns a multi-wire insulated electrical transmission cable wherein each wire comprises a conductor surrounded by an insulation layer. Each conductor has a round cross-section and the majority of the insulation layer of each wire also has a round cross-section. The majority of the outer surface of each insulation layer is concentric with the conductor. The insulation layer of each wire is connected to at least one adjacent wire by a thin web. The resulting cross-section of an adjacent pair of wires basically resembles a barbell design, wherein the web is the bar. Due to the short length and thin cross-section of the web, when one or more of the insulated wires is removed (ripped) from the group, the concentricity of the conductor and insulation layer of each individual wire is preserved.
In another aspect, the present disclosure concerns an insulated multi-wire electrical transmission cable where removal of any of the insulated wires from the other wires results in the removed wire's insulation having a majority of its outer circumference concentric with the outer circumference of the conductor.
In still another aspect, the present disclosure concerns an insulated multi-wire electrical transmission cable where a number of insulated conductors are connected by thin webs. The webs are designed to tear from the insulated wires when a tensile load is applied between two adjacent insulated wires. The web's design which allows this tearing or ripping is manufactured so that the mid-section or neck of the web is thinner than the web where it connects to the insulated wires. Since the web is short, and the neck is intermediate the ends of the web, tearing or ripping of adjacent wires occurs at the neck and as a result it does not damage the insulation of the wires and also maintains the concentricity of the conductor with the insulation layer.
In another aspect, the present disclosure concerns an insulated, multi-wire electrical transmission cable having a plurality of side-by-side wires with adjacent pairs of wires frangibly joined by a web. The overall width of the cable is minimized by facing chordal segments of the outer circumference of adjacent wires' insulation layers. The chordal segments truncates the cross-section of the insulation layers, allowing them to be joined by a short web that permits close packing of the wires.
The present disclosure is directed to an electrical cable suitable for transmission. Transmission cable is distinguishable from communication cable in that communication cable has two concentric, dielectric layers surrounding a central core conductor, whereas transmission cable normally has only a single dielectric layer. Typically the inner dielectric layer of a communications cable is a foam layer and the outer dielectric layer is a tough, protective layer made of a material such as PVC, nylon or other suitable materials. The foam layer is necessary to minimize the impedance of the cable. A transmission cable does not have a foam layer.
A first embodiment of a transmission cable 8 according to the present invention is shown in
Adjacent pairs of wires 10/20 and 20/30 are frangibly joined by webs 40 and 42. Details of one of the webs 40 are best seen in
The web also has a neck 48 intermediate the first and second ends 44 and 46. The neck is the point of smallest cross-sectional area of the web. The cross-sectional area referred to here is that taken along line A-A in
When it is desired to separate an individual wire from its adjacent wire a user will pull the two wires of the pair apart which will result in a tensile load being applied to the web. This will in turn cause the web to break at the neck. Since the neck 48 is intermediate the first and second ends 44, 46, the break point will be remote from the outer surfaces of the adjoining insulation layers. This assures the insulation layer will not be damaged or compromised in its dielectric capacity by the separation process. It also assures that the outer surface of the insulation layer will be essentially concentric with the conductor. Accordingly, standard wire strippers can be used to remove the insulation layer without impinging on or otherwise damaging the conductor. Concentricity of the insulation and conductor is critical when using a clamping concentric stripper. If the concentricity of the stripper, insulation and conductor is not perfect, the strands of the conductor can be damaged. Such damage deters the conductor's ability to properly transfer the electrical energy.
It will be appreciated that with the neck 48 located intermediate the first and second ends 44, 46 of the web, a portion of the severed web will remain on each of the adjacent wires. That is, a slug of the web will remain attached to the outer surface of each insulation layer of the adjoining wires. These slugs are not of sufficient size to interfere with any subsequent stripping operation. A wire stripper will easily cut through the slug as it cuts through the insulation layer.
While the cross-section of the web 40 shown in
Turning now to
Where pairs of wires lie adjacent one another the outer surfaces of the insulation on facing portions of the pairs have a truncated cross-section defined by chordal segments. That is, the actual cross-section of the wires is truncated with respect to an imaginary, full 360° circular cross-section. This is due to the fact that the center-to-center distance between pairs of adjacent wires is less than the sum of the radii of the adjacent wires' insulation layers. Thus, the outside wire 60 has two colinear chordal segment 68 and 69. Similarly, the outside wire 80 has two colinear chordal segment 88 and 89. The middle wire 70 adjoins the two outer wires 60 and 80 and thus has four chordal segments, including collinear chordal segments 75, 77 facing wire 60 and collinear chordal segments 78 and 79 facing wire 80.
The pairs of collinear chordal segments would define most of a chord of an imaginary, full 360° circular cross-section. As can be seen in
Also, for purposes of this disclosure, the insulation layers of cable 54 are considered to define a circular cross-section even though the circular portion of the insulation layer does not extend a full 360°. The insulation layer extends in a circular cross-section sufficiently to define what the diameter is and where it lies, even though the cross-section is truncated at the chordal segments. It will be appreciated that the chordal segments permit a smaller center-to-center distance between adjacent wires, allowing the side-by-side wires to be closer to one another, thereby minimizing the overall width of the cable. This also reduces the weight of the cable per unit length.
The chordal segments merge with a frangible web. One web is shown at 90 and another at 92. The webs 90, 92 have a similar function to the webs 40, 42, although webs 90, 92 have a different shape, namely an arcuate shape with a minimum thickness at the center of the web. Details of one of the webs 90 are best seen in
Placing the neck intermediate the ends of the web assures that when a wire is separated from the cable the point of separation will be in the web and not in the insulation layer. This is particularly helpful in the design of
It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modification can be made without departing from the spirit and scope of the invention disclosed herein.
