IE920158A1 - Manufacture of cables - Google Patents

Abstract

A process for the manufacture of a cable comprising paying off a wire*from a drum, splitting the wire into strands, and double twist 5 bunching the strands into a cable wherein the wire is tensioned and Λ 6 paid off from the drum by a flier arm to remove inherent twist from the t 2- z'J·' wire, the wire is split by a separating device into individual strands, and the individual strands are positioned relative to each other by positioning means before being passed through the double twist buncher 1# so that the strands can be double twisted into a cable in a single pass through the double twist buncher, the wire and individual strands being carried by pullies having a flat drum portion.

Description

This invention relates to the manufacture of cables and more particularly to the manufacture of multi-stranded flexible conductors.

The make up of an electric cable is determined by the function which the cable has to perform. However, in general, the manufacture of an electric cable comprises three main steps. The first step comprises conductor forming i.e. wire drawing and annealing, wire coating, bunching and stranding. The second step is concerned with insulating and sheathing the conductor. The most common form of insulating and sheathing consists of extruding plastics material onto the conductor. The third step in the manufacture of an electric cable consists of assembling the insulated conductors by taping, braiding and armoring etc.

In modern cable manufacture, the conductor can be made up from concentrical layers of a defined maximum number of strands which are wrapped around a central strand e.g. 1+6,+12,+ 18 etc. The outer strands are wrapped around the inner strands in multiple groups of six so that, for example, in the case of a cable made up of 19 strands the - 3 outer layer is made up of a layer of 12 strands surrounding a layer of 6 strands which in turn surrounds the central strand. This rule also applies where three central strands are used e.g. 3,+9,+ 15 etc. In this process, it is essential that the position of each strand relative to every other strand be kept constant. Furthermore, each layer of strands is twisted in an alternate direction. Conductors formed using this method are typically firm, compact and flexible. This process is termed a stranding process? A bunching process can also be used for forming the conductor.

In a bunching process, the individual strands of the conductor are twisted about one another in a random manner without regard to the formation of defined layers about a central strand. It is not necessary to maintain the position of each strand constant relative to the other strands. The strands are therefore naturally positioned i.e. bunched within the conductor.

In the manufacture of multi-stranded flexible conductors a bunching process or a stranding process may be used. The bunching process used is traditionally known as double twist bunching in which a double twist is imparted to each strand during the bunching process. An advantage of the double twist bunching process in the manufacture of multi-stranded flexible conductors is that the process is a high speed one. However, a disadvantage associated with this process is that the resultant conductor is irregular. More particularly, the circumference of the conductor is highly irregular due to the random manner in which the individual strands of the conductor are bunched so that the thickness of insulation, i.e. plastics about the central conductor, varies. Accordingly, it is difficult to control the thickness of the insulation about the central conductor and this variation in thickness can lead to wastage of the plastics insulating material.

Furthermore, excessive amounts of plastics insulating material surrounding the conductor increases the weight of the cable.

Lightweight cables are preferred by car manufacturers as the overall weight of a car is reduced which results in a concomitant reduction in fuel consumption. Similarly, the volume of the cable is also reduced which results in space saving in car manufacture. - 4 I In an attempt to overcome the problems associated with the bunching process in the manufacture of multi-stranded flexible conductors the stranding process has been used. In the stranding process, the resultant conductor has a regular circumference so that a thinner insulation layer may be used about the conductor and hence wastage of plastics insulation is reduced. However, the stranding process utilized in the manufacture of a multi-stranded flexible conductor has the disadvantage that the twist in the wires of each layer of the conductor must be reversed. Accordingly, in the manufacture of these conductors more than one pass or path is required through the stranding machine.

A further disadvantage associated with existing methods of manufacturing multi-stranded flexible conductors is that production speed is limited by the inherent twist in the wire used in the manufacture of the conductor. The inherent twist is imparted to the wire during drawing of the wire and is measured in terms of its lay length which is equivalent to the wavelength of a wave. As the lay length is increased the production speed is increased. However, at present the inherent twist in the wire limits the lay length which in turn limits the production speed.

Furthermore, cable manufacture is frequently interrupted by breakage of the individual strands. Breakage of the strands frequently results from variations in the tension on the strands during manufacture.

An object of the invention is to provide a process for the manufacture of a multi-stranded flexible conductor which is continuous, high speed and which produces a conductor having a regular ’ circumference.

According to the invention there is provided a process for the manufacture of a cable comprising paying off a wire from a drum, splitting the wire into strands, and double twist bunching the strands into a cable wherein the wire is tensioned and paid off from the drum by a flier arm to remove inherent twist from the wire, the wire is split by a separating device into individual strands, and the - 5 individual strands are positioned relative to each other by positioning means before being passed through the double twist buncher so that the strands can be double twisted into a cable in a single pass through the double twist buncher. The wire and individual strands are carried by pul lies having a flat drum portion.

Preferably, the flier arm is rotatable about the drum, the wire being removable during rotation and the angle of incidence between the line of departure of the wire and the drum being kept to a minimum so that the inherent twist in the wire is removed during pay off.

More preferably, the separating device comprises a separator roller having flat grooves in which each strand of the wire is threaded and a winding drum over which the strands are threaded for driving the separated strands towards the twist buncher.

Suitably, the positioning means comprises a gathering plate having a series of openings through which each strand passes. Preferably, the positioning means further comprises a die at which each of the strands from the positioning means converges.

In an alternative embodiment the invention provides an apparatus for the manufacture of a cable comprising splitting means for splitting an individual wire into strands, tensioning means for tensioning the wire and the strands, pul lies for carrying the wire and strands through the apparatus and a double twist buncher for assembling the strands into a cable wherein the paying off means comprises a flier arm rotatable about a clutch mounted on the drum, the wires are split by a separating device and each individual strand is passed through a hole in a positioning means to position the strands before entering the double twist buncher so that the strands can be double twist bunched in a single path through the double twist buncher.

Preferably, the wire and individual strands are carried by pul lies having a flat drum portion so that the wire and strands travel equal distances through the apparatus and the positioning means comprises a gathering plate having openings through which each strand passes. - 6 Preferably, the separating device comprises a separator roller having flat grooves and a winding drum for driving the separated strands towards the twist buncher.

An embodiment of the invention will now be described having regard to the accompanying drawings in which: Figure 1 is a side elevation of a drum around which wire is wrapped having a flier arm attached thereto; Figure 2 is a schematic representation of the splitting and tensioning process showing the removal of the wire from the drum of Figure 1 and the splitting and tensioning of the wire; Figure 3 is a front view of the schematic representation of Figure 2; Figure 4 is a front elevation of a flat pulley for use in the manufacturing process of the invention with the configuration of a standard curved pulley shown in broken lines; Figure 5 is a projection of the separating component of the splitting and tensioning apparatus; Figure 6 is a side elevation of the bunching machine for use in assembling the split and tensioned wire into a cable, and Figure 7 is a schematic diagram of the wire path through the buncher of Figure 6.

Figure 8 is a schematic diagram of the arrangement of drums required for the manufacture of a cable made up of nineteen wire strands.

Figure 1 shows a side elevation of a drum 1 having a diameter D around which wire 2, made up of strands, is wrapped for storage purposes. The wire 2 wrapped around the drum 1 has an inherent twist imparted to the wire during its manufacture using a multiwire drawing - 7 process. The inherent twist and tension on the wire 2 is determined by the diameter, D, of the drum. The diameter, D, is made up of the diameter of the drum 1 proper together with the thickness of any wire 2 remaining on the drum. The drum 1 has an upper end plate 3 and a lower end plate 4. A fixed clutch 5 is mounted on the upper end plate 3.

A flier arm 6, rotatable about the drum 1, is attached to the fixed clutch 5 by a horizontal member 7. The horizontal member 7 is connected to a vertical roller 8 by a pulley 9. A second end pulley 10 is mounted at the other end of the vertical roller 8 while a third pulley 11 is mounted on the fixed clutch 5. The flier arm 6 is rotatable about the vertical axis of the drum 1 on the fixed clutch 5.

The arrows indicate the path followed by the wire 2 over the pulleys 9, , 11 once paid off from the drum 1.

Figure 2 shows a schematic representation of the splitting and tensioning apparatus for use in splitting and tensioning an 'individual wire 12 paid off from the drum 1 and threaded through the equipment.

The drum 1 is positioned within the splitting and tensioning apparatus so that the wire 2 may be paid off into the apparatus. The splitting and tensioning apparatus has two separating guides 13 mounted below a top return pulley 14. The separating guides 13 are ceramic and resemble two eyelets. The separating guides 13 separate the wire 12 into two groups 22 of wire strands which are passed over the top pulley 14 to a separating device 15. The pulley 14 is a flat pulley which is described more fully below. The separating device 15 is mounted adjacent the drum 1 into which the two groups of strands 22 are fed from the pulley 14 and from which the strands are directed to a gathering plate (see Figure 6).

Figure 3 shows a front view of the schematic representation of Figure 2. As shown in the figure, the two ceramic guides 13 are mounted either side of the axis defined by the fixed clutch 5 and the top pulley 14. The ceramic guides 13 split the group of six strands and guides the two groups of three strands 22 to the top pulley 14.

Figure 4 shows a front elevation of a flat pulley as used in the apparatus of the invention. The flat pulley has two end flanges 16, 17 - 8 connected by a drum portion 18. The drum portion 18 is cylindrical in shape so that its outer wall 19 is flat and is oriented at r’ight angles to the end flanges 16, 17. The shape of the drum portion of a standard pulley as used in the prior art is shown in broken lines. The drum portion 20 of the pulley of the prior art is concave which results in twists being imparted to strands running over the drum portion 20. Furthermore, the concave drum portion 20 results in differing path lengths through the apparatus for strands which run over different parts of the drum portion 20. Different path lengths can result in variations in tension on individual strands which can result in strand breakages.

As shown in the Figure, the flat nature of the drum portion 18 of the pulley results in individual strands 21 being arranged in a flat parallel manner against the outer wall 19 of the drum portion 18. Therefore, the individual strands 21 are evenly spaced and travel a defined path which clearly is not the case with the drum portion 20 of the standard pulley. Variations in tension and path length are therefore minimised.

Figure 5 shows an enlarged view of the wire separating device 15 shown in Figure 2. The separating device 15 receives the two groups of three strands 22 from the pulley 14. The separating device 15 is made up of a separator roller 28 and a winding drum 30. The separator roller 28 has grooves 29 in which each strand is threaded. The separator roller 28 is mounted over the winding drum 30 which drives the separated strands towards a twist buncher 31 (see Figure 6).

Figure 6 shows the twist buncher 31 for use in twisting the individual separated strands. Separated strands enter the buncher 31 from the splitting and tensioning apparatus via a gathering plate 43 t having a series of spaced holes through which single strands pass and a closing die 44 made up of a single opening where the strands converge.

The separated strands are guided into the buncher 31 from the closing die 44 by a first large diameter ball bearing pulley 32 mounted at one end of the buncher 31 and is guided from the buncher 31 by a second large diameter ball bearing pulley 33 at its other end. - 9 The pulleys 32, 33 are mounted either end of a cradle 34 defined by an upper bow 35 and a lower bow 36. The bows 35, 36 are convex and the cradle 34 is rotatable about its horizontal axis. Rotation of the cradle 34 is effected by a transmission shaft 46 on the horizontal axis 17 of the cradle 34. The pulleys are oriented so that a double twist is imparted to the strands during a single pass through the buncher 22 to pull the strands from the splitting and tensioning apparatus through the buncher 31 and onto a drum portion 41 of a capstan 38.

The cradle 34 encloses a take up bobbin 35 mounted on pintels 36. The bobbin 35 is mounted so that its axis of rotation is parallel to the horizontal rotational axis of the cradle 34. The take up bobbin 35 is actuated by an electric motor and a gear arrangement 37 mounted adjacent the bobbin 35. The pintels 36 are retractable and can be engaged or retracted simultaneously so that the bobbin 35 can be removed from the cradle 34. Retraction or engagement of the pintels 36 may be effected manually or by motorized means (not shown).

The capstan 38 is detachable and is mounted on the bobbin 35 and is rotatable with the bobbin 35 so that bunched cable can be wound around the capstan 38. A traverse 39 is mounted parallel to the axis of rotation over the bobbin 35 and the capstan 38. A sliding pulley 40 is mounted on the traverse 39. The sliding pulley 40 is automatically actuated by means of adjustable abutments at either end (not shown). A wire threaded through the sliding pulley 40 is wound about the capstan 38 so that as the sliding pulley 40 moves along the traverse 39, the capstan 38 is rotated and pulls on the wire. The wire is thereby wound about the drum portion 41 of the capstan 38.

A series of gear controlled drive pulleys 42 is mounted either side of the capstan 38. The series of pulleys 42 together with the capstan 38 and the traverse 39 are also positioned to, firstly, pull the strands from the splitting and tensioning apparatus through the buncher 31 and onto the drum portion 41 of the capstan 38 anti, secondly, to twist the strands in the same direction during a single pass through the buncher 31. The series of pulleys 42 is made up of the ball bearing pulleys 32, 33 the sliding pulley 40 and two additional pulleys 46, 47 (see Figure 7). - 10 It should be noted that the direction of rotation of the cradle 34 can be in the right hand or left hand direction according to choice. The direction of rotation is controllable by adjusting a reverser (not shown) also located on the cradle 34.

Figure 7 shows a schematic diagram of the path followed by the bunched but untwisted wire strands through the buncher 31. The wire pulley 32 of Figure 6 and the series of pulleys 42 are reversed in Figure 7 to more clearly illustrate the wire path. As shown in the Figure, the wire enters the buncher 31 at the drive pulley 32 and is threaded through the upper bow 35 of the cradle 34 to the remaining pulleys of the series of pulleys 42 which are arranged to impart a twist to the wire and to tension the wire. The series of pulleys 42 is made up of five pulleys, the first pulley being the pulley 32, the second pulley being the second drive pulley 33 which drives the wire to the third pulley 46 mounted adjacent the pulley 33. The fourth pulley 47 of the pulley series 42 is mounted diagonally with regard to the pulley 46 between the pulley 46 and the drive pulley 33. The fifth pulley of the pulley series 42 is the sliding pulley 40 which is mounted on the traverse 39 over the capstan 38. It should be noted that a number of secondary pulleys have been omitted from the diagrammatic scheme of the wire path for simplicity.

Figure 8 shows a schematic diagram of an arrangement required for the manufacture of a cable made up of nineteen wire strands.' For the manufacture of such a cable six strands are fed into the apparatus of the invention from each of three drums 1, 48 and 49. The drums 48, 49 are fitted with a flier arm (not shown) as described above. Each of the wires made up of six strands is paid off from each of the drums 1, 48 and 49 as described previously. A fourth drum 50 supplies the nineteenth strand which is passed through the apparatus and about which each of the groups of three strands from the drums 1, 48 and 49 is bunched into a cable and deposited onto the capstan 38.

In the assembly of the splitting and tensioning apparatus for use in the process of the invention the tension of the strands or wire passing through the equipment is crucial. The tension is in part determined by the spacing of the various components of the apparatus - 11 which determines the spacing of the strands and the wire path followed by the wires. As shown in Figures 2 and 3 the following dimensions of the apparatus are critical. Firstly, the spacing between the end plate 4 of the drum 1 and the clutch 5 as indicated by reference numeral 23; secondly, the distance between the pulley 11 on the clutch 5 and the ceramic guides 22 as indicated by the reference numeral 24; thirdly, the distance between the ceramic guides 22 and the top pulley 14 as s. indicated by the reference numeral 25. The tension on the wire strands is further determined by the horizontal distance between the ceramic guides 22 as indicated by the reference numeral 26. The distances between the various components of the apparatus are calibrated to optimise the production process and to eliminate as much as possible undesired twisting of the wire strands during the production of the multi-stranded cable.

The operation and use of the invention will now be described having regard to the accompanying drawings. More particularly, the invention will be described as used in the manufacture of a cable made up of nineteen strands although clearly the invention can be adapted for use in the manufacture of a cable made up of other numbers of strands.

In use, for the manufacture of a cable made up of a total of nineteen wires the arrangement described in Figure 8 is used. The operating process however will be described with reference to the drum 1 for simplicity. The drum 1 around which the wire 2 is wrapped is fitted with the flier arm 6 and the fixed clutch 5. The individual wire 12 is then threaded through the pulleys 10, 9 of flier arm 6 and the pulley 11 on the fixed clutch 5. The angle (x) defined by the drum 1 and the line of departure of the individual wire 12, referred to as the pay off angle, is kept to a minimum. The pay-off angle also determines the tension on the wire during pay-off. A minimal pay off angle ensures that little or no twists are imparted to the individual wire 6 as it is paid off from the drum 1. Furthermore, the angle (x) is selected so that as the wire is paid off by the flier arm 6, the inherent twist in the wire is removed. - 12 As stated above, the distances between the various components of the splitting and tensioning apparatus determines the tension on the individual strands and wire. Therefore, the distance between the vertical roller 6 and the drum 1 is important in determining the tension on the wire 12 as it is paid off from the drum 1. In the present embodiment, the distance between the vertical roller 6 and the drum 1 is approximately 60cm.

In order to reduce further any undesirable twists imparted to the wire all pulleys used in the apparatus described herein are flat as described above to minimise any twisting of the wires which would occur in a concave pulley. Therefore, the wire 12 and strands 21 travels in as straight a line as possible to reduce the number of undesirable twists imparted to the wire 12 and strands 21 during the manufacturing process as it is difficult to remove such twists from the material in the completed cable. The flat pulleys help to ensure that the material of the cable enters and leaves the pulley in a straight line and ensures that no twists are imparted to the material by running the material along the curved face of a standard pulley. The flat pulleys also help to ensure that variations in tension on the strands 21 due to varying path lengths through the apparatus are reduced so that strand breakages due to tensions variations on the strands are also reduced concomitantly.

As shown in Figure 1 the individual wire 12 from the drum 1 is threaded through pulleys 9, 10 on the vertical roller 6 and the pulley 11 on the fixed clutch 5. The individual wire 12 is then directed through the two separating guides 13 where it is divided into two groups of three strands 22.

The groups of strands 22 are then passed over the pulley 14 into the device 15 which is more clearly described in Figure 5. The separating device 13 is made up of the separator roller 28 and the winding drum 30 as previously described. The individual strands of the groups of strands 22 are threaded over the separator roller 28. Each individual strand is positioned in a series of grooves 29 having flat faces as previously described. The individual strands are subsequently wound about the winding drum 30 mounted below the separator roller 28.

•E 920158 - 13 The winding drum 30 is rotatable and rotates to drive the individual strands to the double twist buncher 31.

Therefore, the groups of three strands are split into individual 5 strands before entering the double twist buncher 31. The individual strands are also tensioned before entering the double twist buncher 31, the tension on each strand being determined by the spacing of the individual components of the manufacturing apparatus as previously described.

In the manufacture of a multi-stranded cable made up of nineteen individual strands three pay off drums are used and three wires made up of six individual strands are paid off from each drum and split and tensioned so that a total of eighteen wires from three pay off drums approach the gathering plate 43. This is illustrated schematically in Figure 8.

As shown in the figure, the three pay off drums 1, 48 and 49 contribute eighteen strands in total to the gathering plate 43 and a single central strand 51, from the fourth pay off drum (50) is also tensioned and directed to the gathering plate 43. At the closing die 44, the individual strands converge about the central strand 57.

The traverse 39 is parallel to the drum portion 41 of the capstan 38 so that as the sliding pulley 40 moves backwards and forwards along the traverse 39 and the drum portion is simultaneously rotated the wire is wrapped about the drum portion 41. The combined affect of the path * of the wire through the buncher 31 together with the rotation of the cradle 34 and the drum portion 41 of the capstan 38 imparts a double twist to the wire in a single pass through the double twist buncher 31.

In the present invention, the individual strands are twisted in the same direction so that only one path through the buncher 22 is required and the production speed of the multi-stranded cable therefore increased significantly.

The finished cable is made up of nineteen wires bunched and double-twisted in a single pass. The circumference of the finished - 14 » cable is regular due to the controlled spacing of the individual strands in the apparatus through the use of flat pulleys. The process is a continuous one not prone to interruption due to strict tension control of the strands during manufacture. Removal of the inherent twist from the wire during pay off, spacing of the apparatus components and the use of flat pulleys combine to ensure that a multi-stranded flexible cable can be produced at high speed using a bunching process.

Claims (13)

1. A process for the manufacture of a cable comprising paying off a wire from a drum, splitting the wire into strands, and double twist 5 bunching the strands into a cable wherein the wire is tensioned and paid off from the drum by a flier arm to remove inherent twist from the wire, the wire is split by a separating device into individual strands, and the individual strands are positioned relative to each other by positioning means before being passed through the double twist buncher 10 so that the strands can be double twisted into a cable in a single pass through the double twist buncher.

2. A process for the manufacture of a cable as claimed in claim 1 wherein the wire and individual strands are carried by pul lies having a 15 flat drum portion.

3. A process for the manufacture of a cable as claimed in claim 1 or claim 2 wherein the flier arm is rotatable about the drum, the wire being removed during rotation and the angle of incidence between the 20 line of departure of the wire and the drum is kept to a minimum so that the inherent twist in the wire is removed during pay off.

4. A process for the manufacture of a cable as claimed in any of the preceding claims wherein the separating device comprises a separator 25 roller having flat grooves in which each strand of the wire is threaded and a winding drum over which the strands are threaded for driving the separated strands towards thejtwist buncher.

5. A process for the manufacture of a cable as claimed in any of the 30 preceding claims wherein the positioning means comprises a gathering plate having a series of openings through which each strand passes.

6. A process for the manufacture of a cable as claimed in claim 5 wherein the positioning means further comprises a die at which each of 35 the strands from the positioning means converges.

7. Apparatus for the manufacture of a cable comprising splitting means for splitting an individual wire into strands, tensioning means for tensioning the wire and the strands, pul lies for carrying the wire - 16 10 and strands through the apparatus and a double twist buncher for assembling the strands into a cable wherein the paying off means comprises a flier arm rotatable about a clutch mounted on the drum, the wires are split by a separating device and each individual strand is passed through a hole in a positioning means to position the strands before entering the double twist buncher so that the strands can be double twist bunched in a single path through the double twist buncher.

8. Apparatus for the manufacture of a cable as claimed in claim 7 wherein the wire and individual strands are carried by pul lies having a flat drum portion so that the wire and strands travel equal distances through the apparatus.

9. Apparatus as claimed in claim 7 or claim 8 wherein the positioning means comprises a gathering plate having openings through which each strand passes.

10. Apparatus as claimed in any of claims 7 to 9 wherein the separating device comprises a separator roller having flat grooves and a winding drum for driving the separated strands towards the twist buncher.

11. A process for the manufacture of a cable substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

12. An apparatus for the manufacture of a cable substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

13. A cable whenever manufactured by a process as claimed in any of claims 1 to 6 or claim 11.