GB2244848A - Composite cable and method of terminating cable - Google Patents

Abstract

A composite cable 10 comprises at least two cable components 12, 14 and an outer sheath 28 wherein at least one of the components has either no insulation or insulation of thickness less than 0.1 times the overall diameter of that component. The cable components may be coaxial 12, twisted pairs 14, or insulated conductors with or without screening, or optical cables. In one embodiment (Fig 1) the coaxial cable has no outer insulation. When terminating the cable heat shrink sleeves 30, 32, 36 are provided where the outer sheath 28 has been removed. The sheath 28 may be provided with a rip cord. In another embodiment (Fig 2) a plurality of twisted pairs are arranged around one coaxial cable. The composite cable is thinner and therefore more cables may be installed in a duct. <IMAGE>

Description

A COMPOSITE CABLE AND A METHOD OF TERMINATING A COMPOSITE CABLE This invention relates to a composite cable and a method of terminating a composite cable.

A significant factor influencing the installation cost per subscriber in a ducted cable communication system network is duct occupancy; that is the density of cables installed in the ducting. Where it may be desirable to install multiple communication systems in a single ducted network, the problem of minimising installation cost is multiplied. For example, it may be desirable to install coaxial cable which is used to transmit cable television signals alongside telephony capacity (twisted pair cables).

Previously to install such telephony capacity would normally mean installing separate cables, or installing a cable of combined coaxial/twisted pair construction with a resulting significantly increased diameter. In both cases the presence of the twisted pair cable would significantly reduce the duct capacity and therefore reduce the number of subscribers per installed duct.

To the applicants knowledge there is no known practical way of reducing composite cable diameter whilst presenting each component of the cable in a form which can be readily terminated.

In particular, a conventional coaxial cable connector employs the outer jacket of the coaxial cable to provide connector security via crimping or threading, and this outer jacket must therefore be retained.

With conventional cable components the thickness of the jacket provided for external protection and termination purposes tends not to be less than 0.1 times the overall diameter of the sheathed cable component.

The present invention seeks to provide a composite cable of minimal dimensions to optimise the number of cables in each installed duct.

According to the present invention there is provided a composite cable comprising at least two cable components and an outer sheath around said at least two cable components, wherein at least one cable component has either no insulation or insulation of thickness less than 0.1 times the overall diameter of that cable component.

For the avoidance of doubt for the purposes of the present application by overall diameter of the cable component we mean the diameter of the sheathed cable component.

According to a second aspect of the invention there is provided a method of terminating a composite cable comprising at least two cable components and an outer sheath around said at least two cable components, at least one of said cable components having no insulation or insulation of thickness less than 0.1 times the overall diameter of that cable component, said method comprising providing a sleeve around at least a part of one of said cable components, said part extending from said outer sheath.

Preferably all of the cable components have no insulation or insulation of thickness less than 0.1 times the overall diameter of each cable component and individual sleeves are provided around each of said parts of the cable components which extend from the end of the outer sheath.

In a preferred embodiment of the invention the sleeves may be heat shrunk to their respective cable components and a heat shrink transition provided around the end of the cable outer sheath and at least a part of the individual sleeves. The free ends of the individual sleeves may be stripped for termination purposes, and the exits of the cable components from their individual sleeves may be sealed by injection of suitable adhesive or sealant to form a gasket.

Any of all of the two or more cable components may consist of the following: coaxial cable; screened or unscreened twisted pair cable; screened or unscreened insulated conductors; optical fibre cable.

In order that the invention may be more readily understood a specific embodiment thereof will now be described by way of example only with reference to the accompanying drawings in which Figure 1 shows one embodiment of the present invention; Figure 2 shows a cross section of the cable of figure 1 along the line 11-11; and Figure 3 shows a cross section of a standard cable construction for comparison purposes.

Referring to figures 1 and 2 a composite cable 10 comprises a coaxial cable 12 and a plurality of twisted pair cables 14 only one of which is shown in figure 1. The coaxial cable 1 2 comprises a central wire 16, dielectric 18, copper foil 20 and copper braid 22. The twisted pair cable comprises a pair of wires 24 each bound in a jacket 26. The jacket 26 may be made from any suitable insulating material. Both the coaxial cable 12 and twisted pair cables 14 are bound by an outer sheath 28. A polyester barrier 29 may be located between the interior surface of the outer sheath 28 and the cables 12,14. It will be readily seen from figure 2 that all of the twisted pair cables 14 are provided adjacent one part of the coaxial cable 12 the reason for which will be described later.

The coaxial cable 12 has no sleeve within the outer sheath 28, the twisted pairs being directly adjacent the braided coaxial cabie, but for a thin layer of insulating polyester tape 18 provided around the copper braid 22.

The outer sheath 28 is rounded by pressure extrusion to optimise duct installation.

The composite cable 10 as hereinbefore described is of significantly reduced width compared to prior art cables of this kind.

When the cables 14, 16 are to be terminated the ends of the outer sheath 28 are removed from the cable 10. The ends of the cables 14, 16 are therefore presented for termination without external jackets. As the twisted prior cables 14 are located adjacent one another in the cable construction heat shrink sleeves 30, 32 can be easily located over the twisted pair 14 and coaxial cable 12 respectively. The size of the sleeves 30, 32 is selected to yield a snug fit when the sleeves 30, 32 are shrunk to an extent so as to optimize wall thickness.

The sleeves 30, 32 are fitted as close to the cable outer sheath 28 as possible, and the outer end of the twisted pair sleeve 30 injected with a suitable quantity of self-curing silicone rubber sealant 34 to form a 'gasket' around the pairs 14 as the sleeve 30 shrinks. The sleeved cables 12, 14 are then presented to a heat shrink transition 36 whose dimensions are suitable for one end 38 to shrink down onto the cable outer jacket 28, and the transition end 40 to shrink down onto the two heat-shrink sleeves 30, 32.

The resulting composite cable 10 appears as a sealed unit having a coaxial output 12 with a 'sheath' 32 suitable for standard termination practices, and one or more twisted pairs 14 also jacketed 30 for protection up to the point of standard termination.

The invention will now be further described with reference to the following comparative example comparing the cable of the present invention as illustrated in figure 2 and a standard cable as illustrated in figure 3. Similar reference numerals are used to represent like parts. The jacket of the coaxial cable in the standard construction is labelled 42.

EXAMPLE 1.

This comparison of external diameter is based on British standard 5425 type 445 coaxial cable (6.65mm) with two twisted telephone cables to British Telecom specification CW1308 (0.5mm conductor) and polyethylene outer jacket.

CABLE TYPE DIAMETER STANDARD COMPOSITE CABLE (FIG. 3) 10.00 COMPOSITE CABLE PRESENT INVENTION (FIG. 2) 8.7 It can readily be seen from this comparative example that the cable of the present invention is of significantly smaller diameter than the conventional cable.

Similar favourable comparisions result using the following standard coaxial cables; RG6 COAXIAL (8.4mm); B55425 TYPE 550 (6.65 mm); B55425 TYPE 725 (10.3 mm) and RG11 TYPE COAXIAL (10.3 mm) It is to be understood that the above described embodiment is by way of illustration only. Many modifications and variations are possible.

For example as there is a significant length of outer cable 28 to be received for the cable prior to termination rip cords can be incorporated to ease the installors task in removing the outer sheath 28.

The composite cable 10 may be used in combination with the cable as described in UK Patent 2084927 maintained under the Trade Mark RBS by VOLEX GROUP PLC. As this RBS cable optimises duct fill ratios, duct capacity for coaxial twisted per composites of the type is further improved.

Although the embodiment described herein makes specific reference to a composite cable comprising coaxial cable and twisted pair cables this principle may be applied to any cables such as for example a composite cable comprising any of the following either paired with a similar cable or a different cable; coaxial cable; screened or unscreened twisted pair cable; screened or unscreened insulated conductors; optical fibre cables.

Claims (18)

1. A composite cable comprising at least two cable components and an outer sheath around said at least two cable components, wherein at least one cable component has either no insulation or insulation of thickness less than 0.1 times the overall diameter of that cable component.

2. A composite cable as claimed in claim 1, wherein each of the cable components has either no insulation or insulation of thickness less than 0.1 times the overall diameter of that cable component.

3. A composite cable as claimed in claim 1 or claim 2, wherein a part of at least one of said cable components extends beyond the end of the outer sheath and a sleeve is provided around said part of said cable component.

4. A composite cable as claimed in claim 3, wherein the sleeve is heat shrunk to the cable component.

5. A composite cable as claimed in claim 3 or claim 4, wherein a heat shrink transition is provided around at least a part of the outer sheath and at least a part of said sleeve.

6. A composite cable as claimed in any of claims 3 to 5, wherein the exit of at least one cable component from the sleeve of that cable component is sealed by an adhesive or sealant.

7. A composite cable as claimed in any preceding claim, wherein at least one of the cable components comprises any of the following: coaxial cable, screened or unscreened twisted pair cable, screened or unscreened insulated conductor or optical fibre cable.

8. A composite cable as claimed in any preceding claim, comprising cable components of different diameters, wherein the cable components of the smaller diameter are grouped together.

9. A composite cable as claimed in any preceding claim, comprising a coaxial cable component and a plurality of twisted pair cable components.

10. A method of terminating a composite cable comprising at least two cable components and an outer sheath around said at least two cable components, at least one of said cable components having no insulation or insulation of thickness less than 0.1 times the overall diameter of that cable component, said method comprising providing a sleeve around at least a part of one of said cable components, said part extending from said outer sheath.

11. A method of terminating a cable as claimed in claim 10, wherein all of the cable components have no insulation or insulation of thickness less than 0.1 times the overall diameter of each cable component.

12. A method of terminating a cable as claimed in claim 10 or claim 11, wherein an individual sleeve is provided around each of said parts of the cable components.

13. A method of terminating a cable as claimed in any of claims 10 to 12, wherein at least one sleeve is heat shrunk to the cable component.

14. A method of terminating a cable as claimed in any of claims 10 to 13, wherein a heat shrink transition is secured around the end of the cable outer sheath and at least a part of at least one of said sleeves.

15. A method of terminating a cable as claimed in any of claims 10 to 14, wherein the exits of the cable components are sealed by injection of adhesive or sealant.

16. A method of terminating a cable as claimed in any of claims 10 to 15, wherein at least one of the cable components comprises any of the following: coaxial cable, screened or unscreened twisted pair cable, screened or unscreened insulated conductor or optical fibre cable.

17. A composite cable substantially as hereinbefore described with reference to and as illustrated in Figs 1 and 2.

18. A method of terminating a cable substantially as hereinbefore described with reference to and as illustrated in Figs. 1 and 2.