GB2152735A - Telecommunication cables - Google Patents

Abstract

In a PCM telecommunication cable, two groups 12, 14 of insulated conductors 18 are separated along a diametrical plane by an electrically conductive screen 16 which encloses the groups and comprises a separating panel 24 consisting of a pair of walls 26 and 28 extending transversely between the groups along the plane and, integral with and extending in opposite circumferential directions from adjacent ends of the walls at one end of the panel, a pair of group-bounding portions 34 and 36. Each group-bounding portion 34, 36 has at the other end of the separating panel an end portion 30, 32 which extends at least partly, and preferably wholly, along the diametrical plane adjacent one of the walls. Preferably, at the end 40 of the separating panel 24 adjacent the end portions 30,32, the walls are integral the one with the other. <IMAGE>

Description

SPECIFICATION Telecommunication cables This invention relates to telecommunication cables.

Internal screening of telephone cables has been described in U. S. Patent 3,803, 340 as well as in U.K. Patent Specifications 1,578,158 and 2,028,758.

Typically a communication cable comprises a core which may be either filled or dry, containing a plurality of conductors divided along a separating plane by an electrically conductive screen. In particular the cable may be of substantially circular cross-section and comprise two compartments, each being half of the core, and each being of substantially semi-circular cross-section, and separated by the screen. One compartment is employed for the transmission of signals in one direction and the other is employed for the transmission of signals in the opposite direction.

Adequate screening of the different units is required in order to minimize crosstalk.

The core is typically filled with a water proofing compound and the sheath or sheaths are generally of a thermoplastic material.

Various screen configurations have been proposed in the afore-mentioned patent specifications.

The present invention seeks to provide an improved screen in telecommunication cables of the afore-mentioned type whereby, typically, up to four layers of metal may be used in the separation of the compartments and the tape need only have an adhesive coating on one side.

In one aspect the invention also seeks to provide an improved screen for a telecommunication cable which may be formed by folding a single sheet of screen material.

In accordance with one aspect of the invention there is provided a telecommunication cable comprising a core including a plurality of conductors divided into groups along a separating plane extending transversely through the core, and electrically conductive screen means enclosing said groups and comprising a separating panel consisting of a pair of walls extending transversely between said groups along said plane and, integral with and extending in opposite circumferential directions from adjacent ends of said walls at one end of the said separating panel, a pair of group-bounding portions, each of which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent one of the transversely extending walls.

In accordance with another aspect of the invention there is provided a telecommunication cable comprising a core including a plurality of conductors divided into two groups along a separating plane extending diametrically through the core, and an electrically conductive screen comprising a single longitudinally applied, transversely folded sheet of metal or metal alloy defining a separating panel consisting of a pair of walls extending diametrically between the two groups along said plane, and, integral with and extending in opposite circumferential directions from adjacent ends of said walls at one end of said separating panel, a pair of group-bounding portions each of which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent to one of the diametrically extending walls.

In accordance with yet another aspect of the invention, there is provided a telecommunication cable comprising a core including a plurality of conductors divided into two groups along a separating plane extending diametrically through the core, electrically conductive screen means enclosing the two groups and comprising two longitudinally applied, transversely folded sheets of metal or metal alloy, the sheets defining a separating panel consisting of a pair of walls extending diametrically between the two groups along said plane and each sheet having, integral with and extending circumferentially from one of two adjacent ends of said walls at one end of the separating panel, a portion which bounds one of the two groups and which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent one of the diametrically extending walls.

The invention also provides a telecommunication cable comprising at least two cable compartments isolated from each other by electrically conductive screen, said screen comprising a separating panel extending between said compartments, and a pair of opposed units bounding portions, said separating panel comprising a middle panel comprising a pair of inner walls in opposed relationship, and a pair of outer walls in opposed relationship with said middle panel, each said outer wall extending at least partly along an adjacent opposed inner wall of said middle panel.

In a particular embodiment of these various aspects of the invention, the transversely extending walls are in interfacial contact and each end portion is in interfacial contact with the adjacent transversely extending wall.

Suitably the transversely extending walls are bonded together and to the adjacent end portions. In an especially preferred embodiment, the end portions extend throughout substantially the whole length of the transversely extending walls.

The invention is illustrated in particular and preferred embodiments by reference to the accompanying drawings in which: FIGURE 1 is a diagrammatic transverse crosssectional view of a cable of the invention in a preferred embodiment; FIGURE 2 illustrates schematically the folds in the screen of the cable of Figure 1; and FIGURES 3 to 7 illustrate schematically various configurations of screen in accordance with the invention.

With further reference to Figure 1 a cable 10 comprises cable compartments 1 2 and 1 4 and an electrically conductive screen 1 6.

The cable compartment 1 2 comprises a plurality of insulated conductors 1 8 bound together by a wrapping 20 which suitably may be of a plastic tape, the insulated conductors 1 8 of compartment 14 are bound together by a similar wrapping 22.

Screen 1 6 separates and encloses cable compartments 1 2 and 14, and is formed from a single, longitudinally applied, transversely folded sheet or tape which suitably may be of aluminium or aluminium alloy and has on one surface only (as shown in Figure 2) a layer of plastic material, particularly a plastic material having an adhesive quality, for example, polyethylene or an acrylic acid copolymer.

Screen 1 6 comprises a separating panel 24 and bounding portions 34 and 36 of generally semicircular configuration.

Separating panel 24 comprises a pair of inner walls 26 and 28 in opposed interfacial contact forming a middle panel, and a pair of outer walls 30 and 32.

Outer wall 30 is in interfacial contact with inner wail 26 and outer wall 32 is in interfacial contact with inner wall 28. Suitably walls 26, 28, 30 and 32 are bonded together.

A waterproof sheath 42 surrounds the screened compartments 1 2 and 14 and more particularly surrounds bounding portions 34 and 36.

The screen 1 6 is more particularly illustrated in Figure 2, which shows how it is formed from a single, longitudinally applied, transversely folded sheet.

The sheet (as viewed in Figures 1 and 2), is folded at an upper end to form a fold 40.

Inner walls 26 and 28 extend downwardly from fold 40 in opposed, facing relationship; at a lower end, (as viewed in Figures 1 and 2), the sheet is bent in opposite directions from adjacent opposed ends 38 of inner walls 26 and 28. The sheet extends in opposite directions from the walls 26 and 28 to define substantially semi-circular bounding portions 34 and 36 respectively. The sheet is then bent downwardly (as viewed in Figures 1 and 2) adjacent the fold 40, to form outer walls 30 and 32 which extend in opposed relationship with inner walls 26 and 28.

As more particularly shown in Figure 2, the screen 1 6 comprises a metal sheet or tape 44, particularly of aluminium or aluminium alloy, having an adhesive plastic layer 46 on one side. In assembly the adhesive layers 46 on inner walls 26 and 28 are bonded together and the adhesive layers 46 on outer walls 30 and 32 respectively are bonded to the metal tape of inner walls 26 and 28.

It will be understood that both sides of the metal tape 44 may be coated with the adhesive plastic layer, and this may be advantageous in protecting the metal tape 44 from corrosion, although clearly the layer of plastics need be on one side only in order to effect adhesion as shown in Figure 2.

With further reference to Figure 3, there is shown a variation in which the screen 1 6a is formed in substantially the same manner as the screen 1 6 in Figure 2, but wherein the outer walls 48 and 50 are relatively short as compared with inner walls 52 and 54 and extend only part way along the inner walls.

With reference to Figure 4 there is shown a screen 1 6b which differs from the screen 1 6 as shown in Figure 2 in that the inner walls 56 and 58 are not connected at a fold 40, although the walls 56 and 58 will suitably be adhered together in the manner described in connection with Figures 1 and 2.

The screen 1 6b may be formed from a single sheet or tape as in Figures 1 and 2, which is subsequently cut at a fold 40, or may be formed from separate sheets or tapes.

With reference to Figure 5 there is shown yet another variation in which the screen 16c differs from that in Figure 4 in that outer walls 68 and 70 are relatively short and extend only part way along inner walls 64 and 66.

For convenience the adhesive plastic layer is not shown in Figures 1 and 3 to 5.

With reference to Figure 6 there is shown yet another variation in which screen 1 6d differs from that in Figure 2 in that inner walls 26d and 28d are folded along the semicircular-bounding portions 34d and 36d, respectively, to form a bridge 40d having an upper portion 80 and a lower portion 82.

The inner walls 26d and 28d are bonded together by the adhesive plastic layer 46.

Similarly upper portion 80 and lower portions 82 are bonded together by the layer 46.

Outer walls 30 and 32 are bonded to inner walls 26d and 28d respectively, and to lower portions 82, by the adhesive layer 46.

The bridge 40d provides an extended flux leakage path along the layer 46 of outer walls 30 and 32, between compartments 1 2d and 14d. The extended flux leakage path reduces the amount of flux that leaks from one compartment 1 2d or 1 4d to the other compartment 14d or 12d.

With reference to Figure 7 there is shown yet another variation in which screen 1 6e differs from that in Figure 6 in that inner walls 26e and 28e are folded along semi-circular bounding portion 34e only to form fold 40e.

This variation also provides an extended flux leakage path.

It is also within the scope of the invention to insert an additional layer between the inner walls in any of the embodiments shown in Figures 1 to 5 so as to increase the thickness of the separating panel and improve the separation of compartments 1 2 and 14.

The waterproof sheath 42 may be extruded directly about the screen 1 6 in Figure 1, the fusion temperature of the adhesive plastic layer 46 on the screen 1 6 being low enough for the plastic layer 46 to be fused by the heat of extrusion of sheath 42 over screen 1 6 to form the bond between the walls 26, 28, 30 and 32. The temperature of fusion should be sufficiently low that the insulation on conductors 18 is not damaged.

It will be understood that the space between the conductors 1 8 in compartments 1 2 and 14, in Figure 1, may be occupied by air or may be filled with a water resistent dielectric composition.

Claims (7)

1. A telecommunication cable comprising a core including a plurality of conductors divided into groups along a separating plane extending transversely through the core. and electrically conductive screen means enclosing said groups and comprising a separating panel consisting of a pair of walls extending transversely between said groups along said plane and, integral with and extending in opposite circumferential directions from adjacent ends of said walls at one end of the said separating panel. a pair of group-bounding portions, each of which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent one of the transversely extending walls.

2. A telecommunication cable comprising a core including a plurality of conductors divided into two groups along a separating plane extending diametrically through the core. and a.n electrically conductive screen comprising a single longitudinally applied. transversely folded sheet of metal or metal alloy defining a separating panel consisting of a pair of walls extending diametrically between the two groups along said plane. and, integral with and extending in opposite circumferential directions from adjacent ends of said walls at one end of said separating panel. a pair of group-bounding portions each of which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent to one of the diametrically extending walls.

3. A telecommunication cable comprising a core including a plurality of conductors divided into two groups along a separating plane extending diametrically through the core, electrically conductive screen means enclosing the two groups and comprising two longitudinally applied, transversely folded sheets of metal or metal alloy, the sheets defining a separating panel consisting of a pair of walls extending diametrically between the two groups along said plane and each sheet having, integral with and extending circumferentially from one of two adjacent ends of said walls at one end of the separating panel, a portion which bounds one of the two groups and which has at the other end of the separating panel an end portion which extends at least partly along said separating plane adjacent one of the diametrically extending walls.

4. A telecommunication cable as claimed in any one of the preceding claims, wherein the transversely extending walls are in interfacial contact and each end portion is in interfacial contact with the adjacent transversely extending wall.

5. A telecommunication cable as claimed in claim 4, wherein the transversely extending walls are bonded together and to the adjacent end portions.

6. A telecommunication cable as claimed in any one of the preceding claims, wherein the end portions extend throughout substantially the whole length of the transversely extending walls.

7. A telecommunication cable substantially as hereinbefore described and as shown in Figures 1 to 3, or Figure 4, 5. 6 or 7 of the accompanying drawings.