GB2253421A

GB2253421A - Cable manufacture

Info

Publication number: GB2253421A
Application number: GB9104623A
Authority: GB
Inventors: Lennard Hooper; Malcolm James Montgomery; Roger Gardner
Original assignee: STC PLC; Northern Telecom Europe Ltd
Current assignee: STC PLC; Nortel Networks Optical Components Ltd
Priority date: 1991-03-05
Filing date: 1991-03-05
Publication date: 1992-09-09
Anticipated expiration: 2011-03-05
Also published as: GB2253421B; GB9104623D0

Abstract

The individual pairs of a telecommunications cable are drawn through an array of S-Z twist creators 141 mounted in a generally circular arrangement. Each twist creator is rotated back and forth to provide the corresponding pair with alternate left and right hand twists. The pairs are then laid-up to form a cable. <IMAGE>

Description

CABLE MANUFACTURE This invention relates to cables and in particular to the manufacture of telecommunications cables incorporating insulated conductors. The invention further relates to apparatus for manufacturing telecommunication cables.

In the manufacture of an insulated conductor telecommunications cable groups of twinned conductor pairs are laid up in a single operation to form a cable structure which is then sheathed. In order to minimise cross-talk the conductors of each pair are twisted together prior to the laying up process. The twisted pairs are prepared on a twinning machine and are then stored on reels from which they are dispensed in the course of the cable manufacturing operation. The process of twisting the pairs, storing the twisted pairs and then dispensing the pairs to form a cable is time consuming.

Also the length of a production run of cable is determined by the capacity of the storage reels. This imposes a manufacturing cost on the process and also involves a significant wastage of material.

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

According to one aspect of the invention there is provided a process for manufacture of a telecommunications cable, the process including providing pairs of insulated conductors, and laying said pairs up into a cable, wherein each said pair is provided with alternate left handed and right handed twists prior to said laying up to form the cable.

According to another aspect of the invention there is provided apparatus for manufacturing a telecommunications cable incorporating insulated conductor pairs, the apparatus including means for providing a plurality of said conductor pairs, a haul-through device for hauling the conductor pairs, first twist creator means for laying up the conductor pairs into a cable, and second twist creator means one for each said pair and disposed intermediate the pair providing means and the first twist creator means, each said second twist creator means being adapted to impart sequentially to that pair alternate left-handed and right-handed twists.

The technique simplifies the cable manufacturing process by removing the need for a separate twisting stage, and in particular allows a continuous process to be used thus increasing production rate and reducing waste. In a particularly advantageous arrangement, continuous feed of conductors may be provided by the dispenser arrangement described in our specification No. 2,226,052.

An embodiment of the invention may now be described with reference to the accompanying drawings in which: Fig. 1 is a general schematic diagram of a cable manufacturing apparatus; Fig. 2 is a plan view of the apparatus of Fig.

1; Fig. 3 illustrates the conductor pair twist creator assembly of the apparatus of Fig. 1 and 2; and Fig. 4 shows in more detail an individual twist creator of the assembly of Fig. 3.

Referring to Figs. 1 and 2 groups of single insulated conductors 11 are supplied from dispensing stations 12 via corresponding lay plates 13 to pair twist creator assemblies 14 each of which services one group of conductors. The conductors are pulled through the apparatus by a haul-through caterpillar 15 or by a capstan.

Preferably the conductors are dispensed from a continuous supply arrangement such as that described in our specification No. 2,226,052. In that arrangement conductors are supplied from reels each provided with a corresponding back-up reel, the conductor at the start of the back-up reel being welded to the conductor at the finish of the supply reel. Whenever a supply reel becomes exhausted the back-up reel takes over the supply and a further back-up reel is then provided to continue the process. In this way very long cable manufacturing runs can be achieved.

Each lay plate 13 arranges the conductors 11 of the corresponding group into pairs each of which is then fed into a twist creator 141 of the assembly 14. In the arrangement of Fig. 1 there are five groups of ten conductor pairs, but it will be appreciated that the grouping of the conductors will be modified to suit both the particular cable being manufactured and the number of twist creators provided on each assembly 14.

The purpose of each twist creator 141 is to provide the corresponding conductor pair with alternate left-handed and right-handed twists.

The twisted pairs lia from each twist creator assembly are taken via a series of pulleys where the pairs are grouped together and provided with a binder tape (not shown) in a binder station 16. The bound groups are then drawn via a second lay plate 17 into a cable twist creator 18, the latter providing alternate left-handed and right-handed twists of the grouped twisted pairs whereby the groups may be laid up into a cable.

The laid-up or cabled groups are drawn through the twist creator 18 and through a second binder 19 where a further tape is applied. The assembly may then be reeled up onto a take-up reel 20 or it may be led into an extruder (not shown) for application of a plastics sheath to form a finished cable Fig. 3 and 4 together illustrate the construction of the twist creator assembly 14 in more detail. The assembly includes a plurality of twist creators 141, one for each conductor pair, supported between a pair of parallel mounting plates 142, 143. The mounting plates have each a circumferential array of openings for receiving hollow or tubular pivots 144 whereby the twist creators 141 are rotatably mounted. The conductor pairs are, in use, threaded through these hollow pivots.Advantageously the mounting plate 143 at the downstream side of the assembly supports an array of idler pulleys 145 whereby conductor pairs twisted by the assembly may be concentrated prior to entry into input die 146 of the binder station 16 (Figs. 1 and 2).

As can be seen from Fig. 4, each twist creator comprises an array of mutually off-set idler pulleys 147 supported between a pair of parallel plate members 148.

The conductor pairs are led over the pulleys 147 so as to follow an angled or zig-zag path through the twist creator. To impart a twist to the conductor pair the twist creator is rotated in alternate directions about the spindles or pivots 144. For this purpose the twist creator may be provided with a gear wheel 148 driven via a drive motor (not shown). Typically the twist creator is rotated a number of turns in a first direction to impart a twist to the conductor pair. The device is then held stationary for a time to allow the back twisted (i.e.

upstream) region of the pair to be pulled through before the twist creator is rotated in the opposite direction to twist the next length of conductor pair. In this way each conductor pair receives alternate right-handed and left-handed twists along its length.

The number of twists per metre of conductor is determined by the conductor through-put rate, the number of turns that the twist creator is rotated, and by the distances between the lay plate 13 and the twist creator assembly 14 (the input distance), and between the twist creator assembly and the binder station 15 (the output distance). We have found that a ratio of input distance to output distance in the range 10:1 to 20:1 is suitable for throughput speeds of 100 to 200 m/min.

The technique described above is of particular advantage in the continuous production of cable. This significantly reduces the number of occasions when the coiling machinery has to be 'threaded' with conductor pairs to start-up thus resulting in a reduction both in 'down time' and in material wastage.

Claims

1. A process for manufacture of a telecommunications cable, the process including providing pairs of insulated conductors, and laying said pairs up into a cable, wherein each said pair is provided with alternate left handed and right handed twists prior to said laying up to form the cable.

2. A process as claimed in claim 1, wherein said conductors are provided in groups, said groups being subsequently twisted together to form the cable.

3. A process as claimed in claim 1 or 2, wherein said conductors are provided for a continuous feed supply.

4. A process for manufacture of a telecommunications cable substantially as described herein with reference to and as shown in the accompanying drawings.

5. Apparatus for manufacturing a telecommunications cable incorporating insulated conductor pairs, the apparatus including means for providing a plurality of said conductor pairs, a haul-through device for hauling the conductor pairs, first twist creator means for laying up the conductor pairs into a cable, and second twist creator means one for each said pair and disposed intermediate the pair providing means and the first twist creator means, each said second twist creator means being adapted to impart sequentially to that pair alternate left-handed and right-handed twists.

6. An apparatus as claimed in claim 5, wherein said first twist creator means comprises one or more arrays of twist creation devices, there being one device for each two said conductors.

7. An apparatus as claimed in claim 5 or 6, wherein each pair of conductors is twisted over an input length and each output length by the first twist insertion means, the ratio of said input and output together being from 10:1 to 20:1.

8. An apparatus for manufacturing a telecommunications cable substantially as described herein with reference to and as shown in the accompanying drawings.

9. A telecommunications cable manufactured by a process as claimed in any one of claims 1 to 4.