GB2339630A - Manufacturing twisted and compacted strands for conductor cables - Google Patents

Description

2339630 METHOD AND APPARATUS FOR MANUFACTURING COMPRESSEDICOMPACTED

CONDUCTORS The present invention relates to a method and apparatus for manufacturing compressed/compacted conductors and specifically, to a method and apparatus for manufacturing compact conductors on single or double twist bunchers, twisters or stranders.

Machines sometimes designated as stranding machines, single and double twist machines have been in use for many years. The object of these types of machines is to combine a number of individual wires and by imparting a single or double twist to them bunch or strand them together.

Typically, the individual strands or wires are payed in from a number of bobbins or coils towards the input end of the machine. The wires are then layered or bunched together at the closing point prior to entry into the machine. This group of wires or strands enters one end of a bow, or rotor, which rotates about the longitudinal axis of the machine.

With double twist machines, the first twist is imparted into the wire due to the rotation of the bow. The group of wires or strands pass along the bow and exit at the other end, passing over a second exit pulley which rotates with the bow. It is from this rotating pulley that the group of wires or strands are imparted with a second twist.

The double twisted cable is then guided and wound on to the bobbin supported within the stationary cradle. Typically guidance is attained through the use of pulleys mounted on the cradle, which is positioned within the space determined by the rotating bow.

There is a desire by cable manufactures to either compact or compress the strand to maximise the conductors capacity for carrying current for a minimum conductor cross sectional area, whilst maintaining the specified flexibility. This also reduces the required volume of insulation needed for a specified cross section of the final or stranded cable, and hence is economically desirable as the cost of the overall finished cable is therefore lowered. To achieve this techniques have been developed to reduce the empty spaces in a stranded conductor by pulling a conventionally stranded cable through closing dies or roller dies. Through this process each wire is randomly deformed and compressed against the others and therefore the same conductivity of a conductor can be achieved with a smaller overall cross-section.

The conventional way producing the compaction of stranded conductors has been through the use of tubular or rigid stranders. However tubular stranders and rigid stranders are expensive machines and attempts have been made to manufacture compact conductors with single twist and double twist machines. Double twist machines are the most productive since a higher number of twists per rotation of the machine can be imparted onto the conductor. However, there are difficulties in achieving an acceptable compact conductor quality. Also it is difficult in providing the large amount of pulling forces that is required to force or pull a stranded conductor through a die in order to compact it within the small confines or limited space within the cradle of these type of machines. In the state- of the-art double twist machines all the compacting must take place in the cradle just before the take-up reel. Therefore, prior art double twist machines had to be run at reduced speeds when producing compact conductors of acceptable quality.

In double twist machines there is a further complication due to the fact that the two twists take place, one at the entry pulley of the bow and the second one at the exit pulley as previously mentioned. As a consequence, the second twist imparted on the already twisted conductors can create unacceptable irregularities in the final stranded conductor prior to compaction. Whilst the twisted cable can be pulled through a die within the cradle, the quality of the finished product limits the application of this machine.

Therefore current equipment does not produce a compact conductor comparable with those that can be manufactured with more expensive and slower machines such as tubular and rigid stranders. In these cases the compaction process can take place outside of the rotating body of the -4 machine and therefore can be carried out with power and/or space limitations being less of a consideration.

In view of the disadvantages inherent in the process of manufacturing compact stranded conductors with double or single twist machines, it is an object of embodiments of the present invention to provide a method and apparatus for manufacturing conductors with an improved quality of compactness at a productive speed.

According to one aspect of the present invention, there is provided a method of manufacturing a twisted and compacted strand comprising a plurality of individual wires including the steps of arranging individual wires into layers and twisting and compacting sequential layers of individual wires.

According to another aspect of the present invention there is provided apparatus for manufacturing a twisted and compacted strand comprising means for supplying a plurality of individual wires, means for receiving and arranging some of the wires into a layer, means for twisting and compacting the layer, means for receiving and arranging other individual wires on the first layer and for twisting and compacting the resultant assembly of wires.

In a preferred embodiment of the invention, the wires are twisted and compacted in rotating compactor units. Advantageously, there is one rotating compactor unit for each layer. Preferably, the or each rotating -5 compactor unit comprises one or more pairs of cooperating rollers.

Adjacent pairs of rollers may be arranged transversely and preferably at right angles to each other. A lay plate and closing die are preferably disposed at the entrance to the or each rotating compactor unit. The twisted and compacted strand is fed from the last rotating compactor unit to a double twist unit comprising a bow, final return pulley, cradle and final compaction unit. The speed of rotation of each rotating compactor unit is approximately twice that of the bow of the double twist unit. This ensures that compaction takes place at the final lay length of the cable and that the assembled wires reform into a circular shape inside the double twist unit.

The means for supplying the wires may comprise a sternpack payoff feeding through a festoon and tension unit.

In order that the invention may be more clearly understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 shows a cross-section through an 18 wire compacted strand, Figure 2a shows a simplified plan view of apparatus for manufacturing the compacted strand of figure 1, Figure 2b shows a side elevational view of the apparatus of figure 1, Figure 2c shows an end elevational view of the apparatus of figure Figure 3a is a plan View to an enlarged scale of part of the apparatus of figure 1, Figure 3b is a side elevational view of the part of the apparatus shown in figure 3a, Figure 4a is a plan view of a pair of rollers forming part of a compactor unit of the apparatus of figures 2a to 2c, Figure 4b is a side elevational view of the rollers of figure 4a, Figure 5a is a plan view of a second embodiment of apparatus according to the invention, Figure 5b is a side elevational view of the apparatus of figure 1, Figure 5c is an end elevational view of the apparatus of figure 1, and Figure 6 is a cross-sectional view through a multi-wire compacted strand produced on the apparatus of figures 5a to 5c.

When producing a 19-wire unilay strand with a common wire size there is a natural tendency for the stand to adopt a hexagonal profile. This can be overcome if a centre 7 wire core can be compacted to a circular shape, but this then causes the outer layer of the remaining 12 wires to be loose around the inner core. If however the outer layer consists of 11 wires, then these can be applied to the compacted core and still make good contact.

-7 The shape of the stranded conductor is now circular and thus when it enters a final compaction unit all wires in the outer layer are compacted equally to produce an arrangement as shown in cross-section in figure 1.

Referring to figures 2a, 2b and 2c, the apparatus to produce the compacted strand of figure 1 comprises a stempack payoff unit 1, a heavy duty festoon and tension unit 2, a first rotating compactor unit 3, a first layplate measuring unit 4, a second rotating compactor unit 5, and a double twist unit 7 comprising a bow 6. In operation, 18 wires from the stempack unit 1 pass into the festoon and tension unit 2. From the exit of this unit 2, the wires take up two different paths referenced P1 and P2. This can be more clearly seen in figure 3a and 3b which shows unit 2 and the first compactor unit 3 and first layplace measuring unit 4 in greater detail. Each compactor unit comprises three pairs of driven rollers 10, 11 and 12 sequentially arranged along the same longitudinal axis but with the centre pair of rollers 11 arranged at right angles to the two outer pairs 10 and 12.

Plan and side elevational views of an exemplary pair of rollers are shown in figures 4a and 4b. In these figures the rollers are referenced 10 and, as can be seen in figure 4a are peripherally shaped to accommodate the strand being compacted.

The wires for the 7-wire core pass straight through a layplate 8 and closing die 9 disposed at the entrance of the first rotating compactor unit 3. The unit 3 rotates at approximately twice the speed of bow 6 in the double twist unit 7. This causes the 7-wire strand forming the core to adopt its final lay length. In this condition the Twire strand is compacted by the driven rollers of unit 3 and then passes into a lay plate 20 and closing die 21 at the entrance of the second rotating compactor unit 5. The wires for the outer layer of the strand pass along path P1 over the top of the first rotating compactor unit 3 and, via two sets of guide pulleys 22 and 23 to the lay plate 20 and closing die 21 at the entrance to the second rotating compactor unit 5. The outer layer of wires is now applied to the compacted 7-wire core and the complete strand enters the second compactor unit 5 in which it is compacted. The compacted strand then enters the double twist unit 7.

Due to the very shallow wire path into the bow and also the self locking effect of the compacted strand, the tendency for the compacted wires to twist is minimised. However by compacting the strand core outside the double twist machine at approximately twice the bow speed, the core should reform into a circular shape inside the machine.

After leaving the bow 6, the strand passes around a final return pulley 26. Once in the cradle 27 of the double twist unit the strand enters a final compaction unit 28 where any imperfections in the overall diameter are corrected. For copper a die compactor should be sufficient.

-9 The rotational speed of each rotating compactor may be varied about a means value. This enables a varying lay to be induced, which prevents the hexagonal formation common with 19-wire unilay and encourages a stable circular balanced construction.

An aspect of the above described method is that almost all the total amount of the energy required to shape the conductor take place outside of the double twist machine at the driven rotating compactor(s). Therefore the power and pulling force required in the cradle is negligible and comparable to the force necessary to manufacture standard, non-compacted stranded conductors. This allows the manufacture of high quality compacted conductors on double twist machines at substantially higher speeds with better surface properties than was previously possible.

The invention can be extended to different layer constructiorns by using multiple rotating compactors. This allows for additional layers to be added to the strand. By way of example, an embodiment employing three rotating compactor units is shown in figures 5a, 5b and 5c. In this embodiment equivalent parts bear the same references as in the embodiment of figures 2a to 2c. The third rotating compactor unit is referenced 30. Still further compactor units may be added as required depending upon the number of wires in the strand. A cross-sectional view of a multi-wire conducted strand produced on the apparatus of figures 5a, 5b and 5c is shown in figure 6. As can be seen, in addition to the central wire, there are three compacted layers of wires.

The above methods and apparatus allows the manufacture of high quality compact strands or conductors on double twist and single twist machines at substantially higher speeds with better surface properties than was previously possible.

It will be appreciated that the above embodiments have been described by way of example only and that many variations are possible without departing from the scope of the invention.

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Claims (12)

1 Apparatus for manufacturing a twisted and compacted strand comprising means for supplying a plurality of individual wires, means for receiving and arranging some of the wires into a layer, means for twisting and compacting the layer, means for receiving and arranging other individual wires on the first layer and for twisting and compacting the resultant assembly of wires.

2. Apparatus as claimed in claim 1. in which the means for twisting and compacting comprise one or more rotating compactor units.

3. Apparatus as claimed in claim 2, in which the or each rotating compactor unit comprises one or more pairs of cooperating rollers.

4. Apparatus as claimed in claim 3, in which there is more than one pair of rollers and adjacent pairs of rollers are arranged transversely to each other.

5. Apparatus as claimed in claim 4, in which adjacent pairs of rollers are arranged at right angles to each other.

6. Apparatus as claimed in any of claims 2 to 5, in which a lay plate and closing die are disposed at the entrance to the or each rotating compactor unit.

7. Apparatus as claimed in any of claims 2 to 6, in which a double twist unit is disposed downstream of the, or the last, rotating compactor unit. '

8. Apparatus as claimed in claim 7, in which the double twist unit comprises a bow, final return pulley, cradle and final compaction unit.

9. Apparatus for manufacturing a twisted and compacted strand substantially as hereinbefore described with reference to figures 1, 2a, 2b, 2c, 3a, 3b, 4a and 4b or to Figures 5a, 5b, 5c and 6 of the accompanying drawings.

10. A method of manufacturing a twisted and compacted strand comprising a plurality of individual wires including the steps of arranging individual wires into layers and twisting and compacting sequential layers of individual wires.

11. A method as claimed in claim 10, in which the means for twisting and compacting comprises at least one rotating compactor unit and a double twist unit comprising a bow is disposed downstream of the, or the last, compactor unit, the speed of rotation of the or each rotating compactor unit being approximately twice that of the bow.

12. A method of manufacturing a twisted and compacted strand substantially as hereinbefore described with reference to figures 1,-2a, 20, 2c, 3a, 3b, 4a and 4b or to Figures 5a, 5b, 5c and 6 of the accompanying drawings.