Cable laying-up apparatus

Abstract

 Apparatus for twisting insulated cores for electric cable comprises a bow-shaped guide 14 fixed to coaxial hollow shaft sections 11a and 11b. The shaft sections are mounted for rotation in bearings 12. A cradle 15 is suspended on bearing 16 from the inner ends 17 of the shaft sections 11a and 11b.
A motor (not shown) rotates the guide and shaft assembly about an axis X.
Insulated core from packs 18, 19 & 20 passes in the shaft 11b through the bearing 16, through the opening 28 in the wall of the shaft 11b to the guide 14, along the guide, through the opening 24 into the shaft 11a and in the shaft 11a through the bearing 12.
The cradle remains stationary as the guide rotates and the cores are twisted once as they pass from the cradle to the rotating guide and once when they pass from the rotating shaft 11a to the machine (not shown) which draws the cores through the apparatus. Thus the cores are given two twists for each rotation of the guide.

Description

[0001] The present invention relates to apparatus for laying up or twisting insulated cores in the manufacture of electric cables.

[0002] One conventional type of electric cable comprises two or more separately insulated cores or conductors covered in a common outer protective sheath. One stage in the manufacture of such cable comprises taking the requisite number of insulated cores wound on different drums, twisting them together, and winding them onto another drum. The layered up or twisted cores from the latter drum are then passed through an extruder in which the outer sheath is extruded over the twisted cores to form the finished cable.

[0003] In a known machine for laying up cable, insulated core is drawn from a plurality of different drums or spools outside the machine.

[0004] The machine comprises a bow-shaped guide which is driven to rotate about an axis which passes through the ends of the bow-shaped guide. The insulated cores pass from outside through an eye near one end of the bow, then together along the bow-shaped guide to the other end where they pass inwardly to within the bow where they are wound onto a drum. The drum is driven separately from the bow to rotate about an axis coaxial with the rotation axis of the bow, and thus draw the cable into the machine. The twisted insulated cores are fed through a traverse mechanism which moves the cores back and forth axially as the twisted cores are wound onto the drum so that the core is wound in layers.

[0005] Each time the bow guide rotates one revolution about the axis, two twists are applied to the cores, a first as the cores pass from outside onto the rotating guide, and a second as the cores pass from the bow guide inside to the traverse mechanism.

[0006] A disadvantage of this arrangement is that it requires slip rings to take power in through the bow guide to drive the drum on the traverse mechanism. The machine has to be stopped when the drum is full and then the drum has to be transferred to the machine which performs the next stage of the cable manufacturing process.

[0007] According to the present invention there is provided apparatus for twisting cores of a cable, comprising a guide, and means for rotating the guide about an axis, a support for mounting a plurality of drums or packs of insulated cores within the guide, the guide being shaped to pass around the insulated cores on the support as the guide is rotated, and the support being mounted so as not to rotate with the guide, and means located outside the guide for drawing core from the drums or packs outwardly in one direction and along the guide to leave the guide in the opposite direction.

[0008] Preferably the apparatus is placed next to a sheath-extruding apparatus and the twisted cores pass directly from the cable twisting apparatus to the extrusion apparatus.

[0009] In this way, the invention can provide an in-line arrangement for supplying twisted core to a sheath-extruding machine.

[0010] Preferably the insulated cores are wound in packs rather than on drums. Drums have a central core and side flanges for retaining the insulated core. A pack may have a core and be mounted on a pallet but is of much lighter construction.

[0011] By using packs rather than drums it is possible to produce three times the amount of cable from one loading compared with the known arrangement. Preferably the core is frusto-conical.

[0012] An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which:-

Figure 1 shows a diagrammatic cross-sectional view of a laying up machine in accordance with the invention; and

Figure 2 shows a detail of the apparatus of figure 1 on an enlarged scale.

Figure 3 shows a schemetic diagram of the apparatus of Figures 1 and 2 in combination with a sheath-extruding machine; and

Figures 4 and 5 show a pallet with a former and a pack of insulated core wound on the former.

[0013] Referring to figure 1, apparatus for twisting insulated core comprises a hollow rotor shaft 11 formed in two sections 11a and 11b and in bearings 12 on stanchions 13. A bow-shaped guide 14 is rigidly secured by its ends to the rotor shaft 11 between the bearings 12, thus joining the two sections together. A cradle 15 is supported from bearings 16 on the inner ends 17 of the shaft sections 11a and 11b. A motor (not shown) is coupled to the outer end of the shaft section 11b for rotating the shaft and guide assembly about a horizontal axis X-X in the bearings 12. The bearings 16 permit the cradle 15 to remain stationary whilst the rotor shaft and guide assembly rotate.

[0014] Means are provided for locating three packs 18, 19 and 20 of insulated core in the cradle. Usually the cores are covered in different coloured plastics insulation, for example brown, blue and green/yellow for conventional 3 core cable. Each pack 18 may comprise a hollow frusto-conical former 42 around which the core 44 is wound, and a pallet base 46 for supporting the pack (see Figures 4 & 5). The means for locating the packs may comprise three posts 21 projecting up from the bottom of the cradle which fit inside the packs of insulated core and support the cores whilst they are being unwound. A guide 22 may be fitted to the top of each post 21 for guiding the cable as it comes off the pack. Each guide 22 comprises an arm twisted about a vertical axis on the post 21 at its inner end and having an eye 23 at its outer end through which the insulated core passes. The arm rotates as the core is drawn from the pack and prevents the core catching the top edge of the pack as it is drawn off, and thus preventing the core becoming tangled.

[0015] The core from the three packs pass through eyes 25 mounted on a bridge 26 extending over the cradle and through three separate holes in a die 27 also carried by the bridge 26.

[0016] From the die 27, the three insulated cores pass into the end of the hollow shaft 11b through the bearings 16 before passing out through an opening 28 in the side of the shaft. As the cores turn at the opening 28 they pass over a roller 29 which prevents abrasion.

[0017] The cores then pass along the guide 14 in the opposite direction to which they left the packs 18, 19 and 20. The cores pass through eyes 30 at intervals along the guide, with roller bearings 31 to prevent abrasion.

[0018] At the end of the bow like guide the cores pass through an opening 24 into the hollow shaft 11a. A roller 32 prevents abrasion as the cores turn to pass along the shaft. The cores emerge from the open end of the shaft section 11a and are then passed to the sheath extrusion machine (not shown). Drive pulleys (not shown) outside the machine apply traction to the cable to pull the cable through the machine.

[0019] The bow-shaped guide 14 is rotated about the axis X-X by a motor (not shown) coupled to the end of the shaft 11b as the cores are drawn from the packs through the guide 14. The rotation of the bow twists the cores twice on each revolution, firstly as the cores pass from the stationary die 27 on the cradle bridge to the rotating shaft and guide assembly, and secondly when the cores pass from the rotating shaft and guide assembly to the next stage of the cable making process. As the direction of the cores movement is reversed between the two positions at which the twisting is applied, the twists are applied in the same sense to the cores resulting in two twists for each revolution of the rotor shaft and guide assembly.

[0020] The use of core packs which do not have substantial centres or flanges, as is the case with drums, means that a greater length of cores can be loaded in the cradle than if drums had been used. This, in turn, means that the machine can run for a longer period of time before it has to be re-loaded.

[0021] Since it is the separate insulated cores that are loaded in the cradle it is easier to perform the loading operation than it is to perform the unloading operation with the drum carrying the twisting cores of the known machine, because each pack will weigh less than a third of the weight of the loaded drum for the same length of cores. This means that reloading the machine can be performed more quickly and easily than unloading the conventional drum.

[0022] Although the twisted cores from the machine could be wound onto a drum for storage before subsequent use, the feature of drawing the twisted cable through the machine from outside the machine means that it is possible to incorporate the core twisting machine 59 into an in-line arrangement with a sheath extruding machine 60 as shown in Figure 3. The drives for advancing the cores through the laying-up machine and the extruding machine may be linked so that the pitch of the twist of the insulated cores remains constant in the sheathed product. A conventional arrangement of weighted pulley for providing an accumulation of twisted cable between the twisting machine and the sheath extruding machine may be used to provide a reserve of twisted cable to for the extruding machine work on whilst the twisting machine is being reloaded, or alternatively the sheathing machine may be immediately adjacent the laying up machine as shown in Figure 3.

[0023] The extruded sheathed cable may be passed from the sheath extruding machine through an accumulator 61 to a pack-winding machine 62.

Claims

1. Apparatus for twisting cores of a cable, comprising a guide and means for rotating the guide about an axis, a support for mounting a plurality of drums or packs of insulated cores within the guide, the guide being shaped to pass around the insulated cores on the support as the guide is rotated, and the supports being mounted so as not to rotate with the guide, and means located outside the guide for drawing core from the drums or packs outwardly in one direction and along the guide to leave the guide in the opposite direction.

2. An assembly comprising apparatus according to claim placed next to a sheath-extruding apparatus wherein the twisted cores pass from the cable twisting apparatus to the extrusion apparatus.

3. An assembly according to claim 2 in which the drives of the cable twisting apparatus and the sheath extruding apparatus are linked so that the cable twisting apparatus gives a constant number of twists per unit length of extruded cable.

4. Apparatus accordng to claim 1, 2 or 3 in which the insulated cores are wound in packs.

5. Apparatus according to claim 4 in which the packs include a conical former and a pallet base.

6. Apparatus according to any of the preceding claims in which the guide comprises a bow-shaped guide member secured at its ends to two coaxial shaft sections mounted in bearings.

7. Apparatus according to claim 6 in which the support comprises a cradle suspended by bearings from the inner ends of the shalf sections, so as not to rotate when the shaft sections are rotated.

8. Apparatus according to claim 7 in which the support includes posts for locating packs of insulated cores in the cradle.

9. Apparatus according to claim 5 or 6 in which the shaft sections are hollow and have openings in their side walls adjacent the ends of the bow-shaped guide the shaft sections and bow-shaped guide defining a path for the twisted cores in which the twisted cores pass in one of the hollow shaft sections through the bearings that support the cradle at one end pass from inside the shaft section at one end through the opening in its side wall onto the bow-shaped guide, pass from the bow-shaped guide into the shaft section at the other end through the opening in its side wall, and pass through the bearings that support the other shaft section insude the other shaft section.

10. A method for twisting together insulated cores for an electric cable comprising drawing cores from a plurality of drums or packs outwardly in one direction along an axis, pasing the cores along a guide which rotates about th said axis around the drums or packs, the twisted cores leaving the guide moving outwardly from the packs or drums along the said axis in the opposite direction to the said one direction.

Drawing