GB1593150A - Method and device for the manufacture of electrical cables - Google Patents

Description

(54) IMPROVED METHOD AND DEVICE FOR THE MANUFACTURE OF ELECTRICAL CABLES (71) We, ASSOCIATED ELECTRICAL IN DUSTRIES LIMITED, of 1, Stanhope Gate, London WIA 1EH, a British Company, and ALAN RICHARD WITHERDEN, a British Subject, of 34, Dene Holm Road, Northfleet, Gravesend, Kent, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention concerns improvements in the manufacture of electrical cable, and relates more especially to a cable twisting device for incorporation in a cable closing machine of the type intended to lay up a plurality of heavy gauge insulated conductors to form a composite cable.The conductors may be of solid or stranded construction in circular or sector-shaped cross-section as used in the manufacture of electrical power cables, general wiring cables and cables for telecommunication.

In the manufacture of composite electrical cables from heavy gauge conductors, for example of extruded aluminium having a sector-shaped cross-section, it is necessary firstly that the conductors must be subjected to the minimum bending stresses during their passage from the supply reel to the laying up die of the cable making machine, and secondly that the supply and take up reels for the conductors and the finished cable must be of relatively large diameter, and thus of correspondingly massive construction in order to enable the duration of each production run of the machine to be as long. and thus as economic, as possible.

These requirements render the design of appropriate cable making machinery extremely difficult, since in order to enable the maximum production speed of the machine to be achieved it is desirable so to arrange the supply and take up reels that the centrifugal forces upon the machine due to its rotation in use are minimised. This conflicts with the requirement that the conductor supply bob bins must be arranged to provide as short, direct and stress-free path as possible for the conductors to travel to the laying up die.

According to one previously known construction of machine, the supply reels for the conductors are arranged in a rotary cradle, being located adjacent one another around the rotary axis of the cradle, and in a common radial plane. In use the cradle is rotated, the conductors are led to a laying up die and are then taken up upon a take up reel, the axis of the take up reel being fixed.

In this machine the axes of the conductor supply reels are located in the relative angular positions determined by the relative angular positions to be adopted by the sector shaped conductors in the finished cable, and sharp bending of the conductors during passage to the laying up head is avoided.

However, the rotary cradle has a large radius and its mass is extremely high. This limits the speed of the machine. Also, the provision of a pit below the cradle is necessary to accommodate the large radius thereof and to enable loading of the cradle with supply reels. The installation cost of the machine is thus very high.

In another known construction, therefore, the conductor supply reels are mounted upon fixed stands, and the conductors are taken up upon a drum the axis of which is rotated in the manner of a so-called drum twisting machine. The radius and mass of the drum twisting machine. The radius and mass of the drum twisting machine is lower than that of a rotary cradle carrying supply bobbins and thus enables a higher rotary speed to be achieved. This arrangement is a considerable advance on the first mentioned proposal, and is the arrangement currently in commercial use.

However, in the interests of economy there is a continued need for ever faster machine speeds. It is accordingly an object of the invention to provide a cable twisting device which achieves higher production speeds than the known arrangements.

In accordance with one aspect of the invention therefore, there is provided a cable twisting device for use in assembling heavy gauge conductors to form a composite cable, said device comprising a single elongated rotary frame formed as a rigid structural unit and incorporating integrally therewith a plu rality of cradles for conductor supply reels each cradle having fixed reel mountings for locating the rotary axis of a corresponding reel, the said reel cradles being arranged in spaced relation along the rotary axis of said frame with the respective reel mountings so arranged that reels may be located therein with the centre of each reel located substantially on the rotary axis of said frame and the rotary axes of respective reels located at right angles to the rotary axis of said frame and angularly relatively displaced about said axis at angles determined by the relative angular positions to be adopted by conductors in the finished cable, and said rotary frame incorporating a plurality of sets of guide means likewise angularly displaced around the circumference of said frame, each set of guide means being so located as to guide a conductor from a corresponding supply reel along a substantially straight path parallel to the rotary axis of the frame to an end of the frame from which said conductors can be fed in common to a laying up die.

The arrangement according to the invention has the advantage that since each of the conductor supply reels is located with its centre, and thus its centre of gravity, on the rotary axis of the said frame, the centrifugal force upon the frame is considerably reduced in relation to that of known constructions, thus enabling the frame to be rotated at higher speeds. with a consequent increase in production. Moreover, owing to the relative angular displacement of the supply reel mountings, and the correspondingly arranged guide means for the conductor, the conductors can be led along a substantially straight guide path into their desired relative angular positions prior to being fed to the laying up die.

Advantageously each of the said sets of guide means comprises one or more sets of guide rollers so shaped and located as to engage the flanks of a sector-shaped conductor and to maintain the conductor in a predetermined orientation relatively to its longitudinal axis. This enables the precise angular orientation of a sector-shaped conductor to be maintained as it is fed from the rotating frame to the laying up die. Thus the minimum twisting force is applied to the conductor during laying up.

When a said set of guide means comprises a plurality of pairs of rollers spaced along the said frame, the said sets of guide rollers may all be aligned at the same relative positions so that a sector-shaped cable is fed from the supply reel to the said end of the rotary frame without being twisted. This is of particular advantage in the case where the conductor comprises an extruded section of aluminium, which does not incorporate any spiral twist. Alternatively, it may in certain cases be desirable for the said sets of guide rollers to be angularly displaced relatively to one another in order to impart a controlled spiral twist to the conductor prior to laying up thereof.

In the conventional method of production of electrical cable incorporating sectorshaped conductors, it is normal practice to apply a layer of tape to the outer circumference of the assembled cores prior to the application of external sheathing which is carried out at a separate operation. However, with the stranding device in accordance with the present invention, the available speed of production is so great that conventional taping heads cannot accommodate the resulting axial speed.

In accordance with a further aspect of the present invention, therefore, a method of producing a stranded cable incorporating sector-shaped conductors includes the steps of laying up the strands of cable by means of a device in accordance with the first aspect of the invention, applying to the outer circumference of the assembled cores a spiral winding of tape, sufficient only to retain the stranded conductors firmly in engagement with one another until wound on a take up reel, and then applying any outer taping layer to the conductors in a separate operation together with the step of applying the outer sheathing of the cable.Thus in accordance with the second aspect of the present invention, the requirement for applying a taped outer covering to the conductors during the initial laying up stage is eliminted, thus enabling the laying up of the conductors to be carried out at a higher speed than in known production methods.

The invention is illustrated by way of example in the accompanying drawings, in which: Fig. I is a side elevation of a device in accordance with the invention for producing stranded electrical cable, and Fig. 2 is a plan view corresponding to Fig.

1.

Referring to the drawings, a stranding device in accordance with the invention comprises an elongated frame I formed as a rigid structural unit and incorporating integrally therewith a plurality of cradles in which are provided mountings for a corresponding plurality of conductor supply bobbins or reels 2, the arrangement being such that the centre of each reel is located upon the rotary axis of frame I and thus of the corresponding cradle, the rotary axis of each reel being at right angles to the rotary axis of the frame I. The frame I is located at its lefthand end. as viewed in the drawings, by means of an end bearing 3, and is supported for rotation by means of a plurality of pairs of rollers 4, upon which rest circular bearing plates 5 of the frame I.The frame I is rotated by means of a motor, not shown, which is coupled to an axial drive shaft 7 extending along the length of the frame via a gearbox 6, the shaft 7 being in driving relationship to the rollers 4, by means not shown. The drive shaft 7 also serves to transmit drive to the whipping head 8 and a haul off capstan 9 by means of appropriate gear boxes 10 and 11.

The frame 1, the whipping head 8, and the capstan 9, are thus geared to one another in order to determine the lay of the finished cable and the pitch of the applied whipping.

The gear box 11 allows for change in the transmission ratio between the drive shaft 7 and the haul off capstan 9, in order to provide for change in the lay of the cable to meet given production requirements. The assembled cores are taken up from the haul off capstan 9 by means of a cable reeling apparatus 12 of generally known type not described in further detail.

Each of the bearing plates 5 of the frame 1 supports guide means 13 for conductors 14 supplied from the reels 2. The guide means 13 may be of generally known type not shown in further detail, for example a set of three guide rollers arranged at angles to one another in order to engage the flanks of a conductor of sector-shaped cross-section.

The arrangement is thus such that a conductor is fed from the supply reel via the guide means 13 along a substantially straight path parallel with the axis of the frame 1, to a guide pulley 15 at the end of the frame, and then passes via a lay plate 16 containing further conductor guide means 17 to a laying up die 18. The lay plate 16 is fixed to the frame 1, for rotation therewith, by means of an axial extension of the frame 1, as shown.

In order to ensure that the conductors 14 reach the laying up head 18 in the predetermined angular relationship in which they are to be laid up in the cable, the reels 2, together with the associated guide means 13, are angularly displaced relatively to one another, about the rotary axis of the frame 1, to provide for appropriate positioning of the conductors 14.Thus, in the arrangement shown which provides for the manufacture of a cable having four sector-shaped conductors, the four supply bobbins 2 are arranged with their rotary axes displaced relatively to one another by 90 . It will be appreciated that the angular displacement of the bobbins will be determined by the number of conductors to be laid up into the finished cable. the angle of relative displacement being equal to 360"/n, where n is the number of conductors in the cable.

In the manufacture of a cable by means of the installation described above, upon transmission of drive to the shaft 7 conductors will be drawn from the rotating frame I, by means of the capstan 9, and will pass along the path indicated, to pass respectively through the laying up die 18. and the whipping head 8, before being taken up by the reeling apparatus 12. The installation described enables laying up to be achieved at a substantially faster rate than hitherto known constructions, for example at a rotary speed of 200 revolutions per minute or more.

WHAT WE CLAIM IS: 1. A cable twisting device for use in assembling heavy gauge conductors to form a composite cable said device comprising a single elongated rotary frame formed as a rigid structural unit and incorporating integrally therewith a plurality of cradles for conductor supply reels each cradle having fixed reel mountings for locating the rotary axis of a corresponding reel, the said reel cradles being arranged in spaced relation along the rotary axis of said frame with the respective reel mountings so arranged that reels may be located therein with the centre of each reel located substantially on the rotary axis of said frame and the rotary axes of respective reels located at right angles to the rotary axis of said frame and angularly relatively displaced about said axis at angles determined by the relative angular positions to be adopted by conductors in the finished cable, and said rotary frame incorporating a plurality of sets of guide means likewise angularly displaced around the circumference of said frame, each set of guide means being so located as to guide a conductor from a corresponding supply reel along a substantially straight path parallel to the rotary axis of the frame to an end of the frame from which said conductors can be fed in common to a laying up die.

2. A device as claimed in Claim 1, in which each of the sets of guide means comprises one or more sets ofguide rollers so shaped and located as to engage the flanks of a sector-shaped conductor and to maintain the conductor in a predetermined orientation relatively to its longitudinal axis.

3. A device as claimed in Claim 2, in which each said set of guide means comprises a plurality of pairs of rollers spaced along the said frame, and the said sets of guide rollers are all aligned at the same relative positions so that a sector-shaped cable is fed from the supply reel to the said end of the rotary frame without being twisted.

4. A cable twisting device substantially as described herein with reference to the accompanying drawings.

5. A method of producing a stranded cable incorporating sector-shaped conductors including the steps of laying up the strands of cable by means of a device as claimed in Claim I, applying to the outer circumference of the assembled cores a spiral winding of tape, sufficient only to retain the stranded conductors firmly in engagement with one another until wound on a take up

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. coupled to an axial drive shaft 7 extending along the length of the frame via a gearbox 6, the shaft 7 being in driving relationship to the rollers 4, by means not shown. The drive shaft 7 also serves to transmit drive to the whipping head 8 and a haul off capstan 9 by means of appropriate gear boxes 10 and 11. The frame 1, the whipping head 8, and the capstan 9, are thus geared to one another in order to determine the lay of the finished cable and the pitch of the applied whipping. The gear box 11 allows for change in the transmission ratio between the drive shaft 7 and the haul off capstan 9, in order to provide for change in the lay of the cable to meet given production requirements. The assembled cores are taken up from the haul off capstan 9 by means of a cable reeling apparatus 12 of generally known type not described in further detail. Each of the bearing plates 5 of the frame 1 supports guide means 13 for conductors 14 supplied from the reels 2. The guide means 13 may be of generally known type not shown in further detail, for example a set of three guide rollers arranged at angles to one another in order to engage the flanks of a conductor of sector-shaped cross-section. The arrangement is thus such that a conductor is fed from the supply reel via the guide means 13 along a substantially straight path parallel with the axis of the frame 1, to a guide pulley 15 at the end of the frame, and then passes via a lay plate 16 containing further conductor guide means 17 to a laying up die 18. The lay plate 16 is fixed to the frame 1, for rotation therewith, by means of an axial extension of the frame 1, as shown. In order to ensure that the conductors 14 reach the laying up head 18 in the predetermined angular relationship in which they are to be laid up in the cable, the reels 2, together with the associated guide means 13, are angularly displaced relatively to one another, about the rotary axis of the frame 1, to provide for appropriate positioning of the conductors 14.Thus, in the arrangement shown which provides for the manufacture of a cable having four sector-shaped conductors, the four supply bobbins 2 are arranged with their rotary axes displaced relatively to one another by 90 . It will be appreciated that the angular displacement of the bobbins will be determined by the number of conductors to be laid up into the finished cable. the angle of relative displacement being equal to 360"/n, where n is the number of conductors in the cable. In the manufacture of a cable by means of the installation described above, upon transmission of drive to the shaft 7 conductors will be drawn from the rotating frame I, by means of the capstan 9, and will pass along the path indicated, to pass respectively through the laying up die 18. and the whipping head 8, before being taken up by the reeling apparatus 12. The installation described enables laying up to be achieved at a substantially faster rate than hitherto known constructions, for example at a rotary speed of 200 revolutions per minute or more. WHAT WE CLAIM IS:

1. A cable twisting device for use in assembling heavy gauge conductors to form a composite cable said device comprising a single elongated rotary frame formed as a rigid structural unit and incorporating integrally therewith a plurality of cradles for conductor supply reels each cradle having fixed reel mountings for locating the rotary axis of a corresponding reel, the said reel cradles being arranged in spaced relation along the rotary axis of said frame with the respective reel mountings so arranged that reels may be located therein with the centre of each reel located substantially on the rotary axis of said frame and the rotary axes of respective reels located at right angles to the rotary axis of said frame and angularly relatively displaced about said axis at angles determined by the relative angular positions to be adopted by conductors in the finished cable, and said rotary frame incorporating a plurality of sets of guide means likewise angularly displaced around the circumference of said frame, each set of guide means being so located as to guide a conductor from a corresponding supply reel along a substantially straight path parallel to the rotary axis of the frame to an end of the frame from which said conductors can be fed in common to a laying up die.

2. A device as claimed in Claim 1, in which each of the sets of guide means comprises one or more sets ofguide rollers so shaped and located as to engage the flanks of a sector-shaped conductor and to maintain the conductor in a predetermined orientation relatively to its longitudinal axis.

3. A device as claimed in Claim 2, in which each said set of guide means comprises a plurality of pairs of rollers spaced along the said frame, and the said sets of guide rollers are all aligned at the same relative positions so that a sector-shaped cable is fed from the supply reel to the said end of the rotary frame without being twisted.

4. A cable twisting device substantially as described herein with reference to the accompanying drawings.

5. A method of producing a stranded cable incorporating sector-shaped conductors including the steps of laying up the strands of cable by means of a device as claimed in Claim I, applying to the outer circumference of the assembled cores a spiral winding of tape, sufficient only to retain the stranded conductors firmly in engagement with one another until wound on a take up

reel, and then applying an outer taping layer to the conductors in a separate operation together with the step of applying an outer sheathing of the cable.

6. A method as claimed in Claim 5, substantially as described herein.