Cable component screening

Abstract

A metal screen is separately wrapped about a number of individual conductors or component groups of a cable using a single wide copper tape in one simultaneous operation. The metal screen tape is passed through a forming die having a number of grooves which shape the tape into a star configuration having radial convolutions forming channels for respective conductors or component groups. The screen tape is then twisted around the components in a continuous operation. This eliminates the need for applying separate tapes to each cable component.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electric cables in which the individual components of the cable are screened from one another and particularly to an improvement providing a common screen for a plurality of separate insulated conductor cable components.

2. Description of the Prior Art

In order to minimize the crosstalk between the individual components of a cable, for example insulated single wires, pairs, quads etc., it is common practice to screen each component part of the cable prior to laying them up to form a cable. This screening comprises the formation of a metallic tubular member around each of the individual cable components. The tubular member can, for example, be formed by longitudinally wrapping a copper tape around a cable component, or by braiding a hose of copper wires around a cable component. Whatever the type of screen used, the steps in the formation of cables with screened components comprise individually screening each cable component along its entire length, and then laying up the individually screened cable components to form a cable. This method suffers from the disadvantage that it is costly in view of the manufacturing time machinery and storage space required.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide an alternative arrangement by which the individual cable components can be screened and laid up together in a common tape in one operation.

According to the present invention there is provided a novel arrangement for screening each of a plurality of electric cable components from one another and laying up the screened cable components, so formed, into a cable in one continuous operation. The individual cable components are simultaneously screened from one another by longitudinally applying a common tape of electrically conducting material to each individual insulated component, and laying up the plurality of screened cable components.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, schematically, a known laying-up arrangement;

FIG. 2 shows, schematically, an arrangement for screening and laying-up according to an embodiment of the present invention;

FIG. 3 shows a view of a first portion of a screen-forming device for use in the arrangement of FIG. 2;

FIG. 4 shows a longitudinal section through the device portion of FIG. 3 taken along line I--I of FIG. 3;

FIG. 5 shows a view of an assembled screen-forming device incorporating first and second portions;

FIG. 6 shows cross-sections through the second portion of FIG. 5 taken at five positions along its length; and

FIG. 7 shows the various cross-sections a single wide metallic tape has before, during and after passing through the screenforming device of FIGS. 3 to 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As previously stated the individual cable components, such as single insulated conductors, pairs of other groups, are normally indvidually screened along their entire length and then the screened components are laid up together to form a cable. A basic prior art arrangement for performing the laying up of the screened components is shown in FIG. 1. The arrangement basically comprises a rotatable structure 1 on which are provided means, for example pintles 2, for mounting reels 3 of the previously screened cable components 4 so that the reels 3 are rotatable about their own axes, in order to permit the cable components on them to be unwound. For the sake of clarity, only three reels have been shown in the drawing, although more than this number may of course be used.

In order to perform laying up of the components 4, their free ends are bunched together and led through a conventional forming die 5 to a take-up reel (not shown), possibly by way of other manufacturing stages, for example helical tape applicators and sheath extruders. By rotating the take-up reel and the structure 1, the screened cable components 4 are pulled off their reels 3 and laid up together to form a cable 6. The length of lay is dependent on the take-up rate and the rotational speed of the structure 1. The forming die 5 serves to form the laid up components into a cable 6 with a predetermined cross-section.

In FIG. 2 there is shown the basic arrangement of apparatus for use in accordance with the screening and laying-up method of the present invention. This arrangement comprises a rotatable structure 7 on which is provided means, for example pintles 8, for rotatably mounting reels 9 of unscreened cable components 10, similar to those in the arrangement for FIG. 1. Also mounted on the structure 7 is a reel 11 of a wide metallic tape 12, for example copper tape. The reel 11 is mounted so that it is rotatable about its own axis for unwinding the tape 12. Rigidly mounted on the end of the structure 7 adjacent a forming die 25 is a device 13 by means of which the wide metallic tape 12 is longitudinally formed at least partially around each of the cable components 10, while a take-up reel (not shown) pulls them off their respective reels, in order to produce screened components 14. As in the arrangement of FIG. 1, laying up of the screened cable components 14 into a cable 15 is achieved by rotation of the structure 7, which includes the device 13.

The device 13 for wrapping the tapes around the cable components can take many forms, but it will basically comprise a number of similar forming tools, the same number of tools as there are cable components, each one of which applies a portion of the wide tape to a separate one of the cable components. The forming tools can, for example, be forming dies, systems of rollers or brushes.

The basic structure of a suitable type of forming device die is shown in FIGS. 3 to 6. This device basically comprises a substantially truncated-conical portion 16, in which grooves 17 are provided. Each of the grooves 17 is associated with a separate one of the cable components 10 and its associated portion of the wide tape 12, so that in the form shown in FIG. 3 there are 8 forming tools in one structure. As can be ascertained from FIGS. 3 and 4 the grooves 17 increase in width and decrease in depth in the direction away from the apex of the cone portion 16. In each of the grooves 17 is a tape guide member 18 (FIG. 5) which has a similar shape to grooves 17, as can be seen from FIG. 6 which shows the variation in cross section of the member 18 between its left and right-hand ends. The guide members 18 are mounted in the grooves 17 so that a slot is provided between the members 18 and the grooves 17. The mounting can be achieved by means, for example, of a collar 19 and screws 20, but a gap must be left between the collar and the walls between the grooves in order that the wide tape may be continuous between adjacent grooves. If a wide flat metallic tape is inserted simultaneously into each of the slots at the right hand end of the grooves 17 and pushed through the slots then it will be formed into a star-shaped member 22 having radial convolutions forming longitudinal channels along the tape, as shown in FIG. 7. An insulated cable component can be dropped into each recess or channel between two adjacent arms of the star-shaped member, if the component is directed along a line similar to line 24 of FIG. 5. Further forming of the metallic tape around the insulated cable conductors can then take place. This may be affected by means of rotation of the structure 7 and the forming device 13 during the laying-up process.

Whilst the invention has been described with reference to a single wide metallic tape simultaneously screening a number of insulated cable component from one another, the method and apparatus using the forming die etc, could alternatively be used with a separate narrow metallic screening tape for each cable component, that is a separate tape for each groove 17 of the die. A separate reel, of tape would then have to be provided for each reel of cable components. In this case the forming die may form the narrow tape into a V-shape and the remaining formation may occur during laying-up, or the forming die may form the tape into a tubular member, with a longitudinal seam, around the cable component.

It is to be understood that the foregoing description of specific examples of this invention is made by way of example only and is not to be considered as a limitation on its scope.

Claims

What is claimed is :

1. A method of screening each of a plurality of electric cable components from one another and laying up the screened cable components, so formed, into a cable in one continuous operation, comprising the steps of feeding a plurality of individual cable components and an electrically conducting screening material along a longitudinal path, forming a plurality of radial convolutions in said material, guiding said cable components into said convolutions, simultaneously screening the individual cable components from one another by longitudinally applying said material to each individual cable component at the same time, and laying up the plurality of screened cable components.

2. A method as claimed in claim 1, wherein the electrically conducting material is a metallic tape.

3. A method as claimed in claim 2, wherein each cable component is screened from the others by a single metallic tape and a forming tool having a plurality of radial convolutions, passing said tape through said tool to form said plurality of convolutions in said tape for receiving respective cable components, and wrapping said tape about said cable components.

4. A method as claimed in claim 3, wherein the metallic tape is a copper tape.

5. Apparatus for simultaneously screening each of a plurality of electric cable components from one another with longitudinally applied electrically conducting material and laying up the plurality of screened cable components, so formed, in one continuous operation comprising a rotatable frame, a plurality of cable component supply reels carried on said frame, a supply reel of electrically conducting material, all of said supply reels being freely rotatable about their own axes, means for forming a plurality of radial convolutions in said material, means for guiding the cable components into the convolutions, each convolution being adapted to accommodate a respective cable component, and take-up means for pulling the cable components through said forming means to wrap said material about said cable components.

6. Apparatus according to claim 5, wherein said material is a metallic tape, said forming means including a truncated conical die having radial channels increasing in width and decreasing in depth along the length away from the apex, and means for guiding said tape into said channels.