GB2253492A

GB2253492A - Improvements in cables

Info

Publication number: GB2253492A
Application number: GB9104992A
Authority: GB
Inventors: Nigel Shackleton; Gavin Morland
Original assignee: Northern Telecom Europe Ltd; STC Ltd
Current assignee: Alcatel Submarine Networks UK Ltd; Nortel Networks Optical Components Ltd
Priority date: 1991-03-08
Filing date: 1991-03-08
Publication date: 1992-09-09
Anticipated expiration: 2011-03-08
Also published as: GB9104992D0; GB2253492B

Abstract

In the manufacture of a cable in which optical fibres 15 are disposed in a grease filled channel 12 in a channel member 11, excess grease is removed by one or more wiper tapes 17, 20 drawn across the channel member in a generally transverse direction. The cleaned channel member may then be sheathed to form a finished cable. <IMAGE>

Description

IMPROVEMENTS IN CABLES This invention relates to a process and apparatus for the manufacture of cables; particularly fibre optic cables.

Various cable designs have been proposed for use in aerial cables incorporating optical fibres. One form of cable currently in use comprises a plastics strength member having one or more surface slot channels each of which accommodates optical fibre elements, the assembly being enclosed in a protective sheath. For many applications it is desirable to fill each channel with a water blocking material such as a grease or gel. Such a construction is described for example in our specification number 2 201 008 A.

A problem that has been experienced in the manufacture of cable of this type is that of removing excess water blocking material prior to the application of the sheath. It will be appreciated that, to ensure complete filling of the channel, it is necessary to provide a small excess of the water blocking material.

Conventionally the filled strength member is pressed through a die fitted with one or more O-rings (a snugger die) whereby excess material is wiped from the surface of the strength member. It has been found that this results in smearing of a thin film of water blocking material over the surface of the strength member resulting in a relatively weak bond between the strength member and the sheath.

The object of the present invention is to minimise or overcome this disadvantage.

According to one aspect of the invention there is provided a method of making an optical cable, including providing an elongate member having a longitudinal open channel, inserting one or more optical fibre elements into said channel, introducing into the channel a water blocking material, closing the channel, removing excess water blocking material from the surface of the elongate member by the application thereto of a flexible tape or wire drawn in a direction generally transverse to the axis of the elongate member, and applying a protective sheath to the elongate member.

According to another aspect of the invention there is provided an apparatus for manufacturing a fibre optic cable, including means for supplying an elongate member having a longitudinal open channel, means for feeding optical fibre elements into said channel, means for filling the channel with a water blocking material, means for closing the filled channel, means for removing excess water blocking material from the surface of the elongate member, and means for applying a protective sheath to the elongate member, wherein the water blocking removal means includes a flexible tape or wire which, in use, is drawn across the elongate member in a direction generally transverse to its axis, whereby to wipe excess water blocking material from the surface of the elongate member.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a general view of the cable manufacturing apparatus; and Fig. 2 is a sectional view of a cable wiper system for use in the apparatus of Fig. 1.

Referring to the drawings, a plastics strength member 11, formed e.g. by pultrusion and having a longitudinal surface short channel 12, is fed trom a storage reel (not shown) through an alignment die 13 and into a fibre insertion station 14. Within the fibre insertion station, optical fibre ribbon elements 15 are guided into the channel 12.

The fibre insertion station 14 incorporates a grease injector whereby water blocking grease or gel material supplied via an inlet pipe 16 is injected into the channel to protect the ribbon elements. To ensure complete filling of the channel a slight surplus of grease is provided. As a result, the filled channel of the member 11 at the exit of the fibre insertion station 14 is slightly overful. This small surplus may be removed by a first wiper tape or wire 17 which is drawn across the channel member 11 in a direction generally transverse to the axis of the channel member.

The filled channel is then closed by a closely fitting sealing strip or cap 18 which is urged into the channel by a suitably profiled roller or pulley 19.

Insertion of the cap 18 displaces a small quantity of grease from the channel 12 and this is removed by a second wiper tape or wire 20, which is drawn across the member 11 as described above. The wiped assembly is drawn through a snugger die 21 to ensure close fitting of the cap prior to the sheathing process to form a finished cable. In some applications the assembly leaving the snugger die 21 may be driven around a large capstan (not shown) to induce an excess length of ribbon fibre element into the channel.

The cleaning apparatus is shown in more detail in Fig. 2 of the accompanying drawings. The tape or wire 20 is drawn from a pay-off reel 31 via an alignment die or guide 32. The tape 20 is drawn over the channel region of the channel member to wipe off excess grease and is then drawn through a further guide 33 and on to a take-up reel 34. The guide 33 removes grease from the tape for collection in a drip-tray 35. The tape 20 is maintained under tension so that it is urged against the member 11.

Typically the tape 20 comprises a polyester.

It is preferred to provide wiping of excess grease both prior to and after application of the cap 18.

However, by control of the grease filling process it is possible to dispense with the first wiper station and to effect wiping of the cable only after application of the cap to the channel.

It is understood that whilst the process and apparatus detailed above are of particular application to the manufacture of aerial cables, they may also be employed in the manufacture of other forms of cable.

Claims

1. A method of making an optical cable, including providing an elongate member having a longitudinal open channel, inserting one or more optical fibre elements into said channel, introducing into the channel a water blocking material, closing the channel, removing excess water blocking material from the surface of the elongate member by the application thereto of a flexible tape or wire drawn in a direction generally transverse to the axis of the elongate member, and applying a protective sheath to the elongate member.

2. A method as claimed in claim 1, wherein further removal of excess water blocking material is effected prior to application of a closure strip to close the channel.

3. A method of making a fibre optic cable substantially as detailed herein with reference to and as illustrated in the accompanying drawings.

4. A cable made by a method as claimed in claim 1, 2 or 3.

5. An apparatus for manufacturing a fibre optic cable, including means for supplying an elongate member having a longitudinal open channel, means for feeding optical fibre elements into said channel, means for filling the channel with a water blocking material, means for closing the filled channel, means for removing excess water blocking material from the surface of the elongate member, and means for applying a protective sheath to the elongate member, wherein the water blocking removal means includes a flexible tape or wire which, in use, is drawn across the elongate member in a direction generally transverse to its axis, whereby to wipe excess water blocking material from the surface of the elongate member.

6. A cable manufacturing apparatus substantially as described herein with reference to and as illustrated in the accompanying drawings.