GB2081764A - Coiling of filament - Google Patents

Abstract

A length of filament, such as wire or optical fibre, is loosely coiled on a flat carrier, in the form of a figure of eight the lobes of which are laid respectively in clockwise and anticlockwise directions. The coil is formed by feeding the filament downwards on to the carrier through a guiding arrangement which causes the downward path of the filament to rotate alternately in clockwise and anticlockwise directions. The guiding arrangement may be a figure of eight shaped double ring structure, with further guide members within the rings, or a gimbal-mounted guide member which is oscillated, by two sets of reciprocating means, about two horizontal axes at right angles to one another. The carrier may be moved to produce the coils shown, and the coils may lie within a container and may be covered with padding. <IMAGE>

Description

SPECIFICATION Filament packaging This invention relates to the packaging of lengths of filamentary material, such as wire or optical fibre, an object of the invention being the provision of a form of package, for one or more filament lengths, which is convenient for transportation and storage, and in which the filament can be maintained free from resultant twist. The invention also relates to a process and apparatus for carrying out the packaging.

According to the invention, a filament package consists of one or more lengths of filament lying loosely coiled on a plane surface of a flat carrier and covered with a layer of padding material, the carrier being integral with or inserted into a shallow container in which the assembly of carrier, filament coil or coils and padding is enclosed, wherein the coil, or each coil, is composed of two lobes together forming substantially a figure of eight and consists of a multiplicity of turns, each of which is laid in said two lobes, the filament forming one lobe of each turn being laid in a clockwise direction, and the filament forming the other lobe of each turn being laid in an anticlockwise direction.

If desired, the coil carrier may be provided with a surface layer of padding material on which the coil is laid. This padding, and that covering the coil, may consist of any soft, resilient material, such as felt, foam rubber, or plastics foam. The padding, whether both underlying and covering the coil, or only covering it, prevents movement of the turns of the coil during transit, and protects the filament from damage. The carrier may be constituted by the bottom of a-suitable container, such as a shallow carton provided with a lid or flaps which, when closed, lies or lie on the padding covering the coil. Alternatively the carrier may be a flat board or shallow tray which, after the filament coil has been laid thereon and covered with padding, is inserted into a closely fitting carton or metal container.If it is required to incorporate a plurality of lengths of filament in a single package, these are laid on the carrier consecutively, and preferably spaced apart by a layer of padding material.

It is to be understood that the phrase "substantially a figure of eight", as used above with reference to the form of the coil, means that the conformation of the coil, and of each turn thereof, is not necessarily that of a true figure of eight, that is to say the lobes may not be circular but may be, for example, elongated in one direction, producing a distorted figure of eight.

However, the shape of the coil, and of the individual turns thereof, will hereinafter be referred to as a "figure of eight" for brevity. The actual shape of the lobes will depend upon the physical properties of the filament, and upon the conditions, and form of the apparatus, employed for laying it down. Preferably the two lobes of the figure of eight are of substantially equal area, the figure being symmetrical about the junction between the lobes in the case of the complete coil, and about the point at which the filament of one lobe crosses over the filament of the other lobe, in the case of each individual turn of the coil.

Preferably the said crossover point of the second and each successive figure of eight turn of the coil is displaced from the preceding crossover point in a direction orthogonal to the longitudinal axis of the figure of eight and in the plane of the respective turn of the coil. Such displacement of the crossover points prevents the build-up of an excessive thickness of the coil at the junction between the lobes, as compared with the thickness in the remainder of the lobes, and also causes some displacement of the lobes in successive turns of the coil, so that the lobes of the complete coil are of substantial width: this arrangement ensures stability of the coil structure, and prevents interlinking of the coil turns.

A process in accordance with the invention for forming a filament coil of substantially figure of eight conformation, in the production of a filament package of the form described above, consists in feeding a length of filament continuously downwards at a controlled speed, on to the upper plane surface of a horizontally disposed carrier, through a guiding arrangement whereby, for the deposition of each figure of eight turn of the coil on the carrier, the downward path of travel of the filament is caused to rotate in a clockwise direction to describe a first lobe of a figure of eight and in an anticlockwise direction to describe a second lobe of a figure of eight, such clockwise and anticlockwise rotations being effected alternately during the deposition of the whole length of filament.

In a first method of carrying out the abovedescribed process for forming a said filament coil.

the filament is fed downwards through a horizontally disposed figure of eight shaped structure having a gap in the junction of the two lobes of the figure of eight, and the downward path of travel of the filament is caused, by stationary guide means co-operating with the figure of eight structure, to rotate alternately within one lobe of the said structure in a clockwise direction and within the other lobe of said structure in an anticlockwise direction.

In a second, and preferred, method of carrying out the above-described process for forming a said filament coil, the filament is fed downwards through a gimbal mounted guide member while the said member is caused, by means of the gimbal mounting, to oscillate about two horizontal axes at right angles to one another, the relative frequencies and relative phases of the oscillations about the respective axes being so controlled that the downward path of travel of the filament between said guide member and the carrier describes a figure of eight whose longitudinal and transverse axes lie parallel to the respective axes of oscillation of the said member.The size, that is to say the area of periphery, of the turns of the coil is controlled by the speed of oscillation of the guide member in relation to the speed of downward travel of the filament: thus, either or both of these speeds can be adjusted to obtain a coil of a desired size, within limits dictated by the inertia and bending capability of the filament.

In either of the above methods, displacement of the crossover points in the centres of successive figure of eight turns of the coil can be effected by slow translation or reciprocation of the carrier in the horizontal direction orthogonal to the longitudinal axis of the coil, while the filament guiding arrangement is maintained in a constant location. Alternatively, if desired, a circular, or figure of eight, or other more complex form of motion may be imparted to the carrier.

One form of apparatus for forming the filament coil by the said first method includes a figure of eight shaped structure, horizontally disposed above the filament receiving carrier, formed of two rings meeting substantially tangentially but with a gap in the junction between the rings, means for guiding the fialment path vertically downwards, from a source at a level above that of the said rings, to a point in the vicinity of the junction between the rings, and guide means co-operating with the rings to cause the further downward path of travel of the filament to rotate alternately within one ring in a clockwise direction and within the other ring in an anticlockwise direction.

The double ring structure is suitably formed of wire, or may be formed by cutting circular apertures in a metal plate. The structure may be mounted in a frame supported by legs resting on the floor (or other surface) outside the filamentreceiving carrier, or may be supported in the required position by any other convenient means.

The rings are preferably of equal diameter, to produce a symmetrical figure of eight coil as aforesaid. The size of the turns of the coil is controlled by the diameter of the rings.

The said guide means co-operating with the rings suitably includes a pair of guide members located respectively within, and at the level of and/or below, the two rings, and at least partly adjacent to the said gap. Each such guide member is so positioned, in relation to the width of the gap, that said member is contacted by the filament immediately after the latter has passed through the gap, and each said member is shaped so as to deflect the filament into a path of travel rotating in the direction opposite to that which it previously followed, and closely adjacent to the ring.If required, depending upon the positions of the said guide members within the rings, an additional guide means in the form of a member projecting from one of the points of junction between the rings is provided, to reduce the width of the gap and to ensure that when the filament passes from one ring to the other, around the free end of the projection, the unconstrained path of the filament will bring it into contact with the guide member within the second ring.

A preferred form of apparatus for forming a figure of eight filament coil by the said second method includes a filament guide member consisting of a plate horizontally disposed above a flat filament-receiving carrier and mounted on a vertical shaft, with a central channel through the plate and shaft for the passage of the filament downwards therethrough, a gimbal mounting arrangement for said guide member consisting of a fixed horizontally disposed outer ring and an inner ring pivoted on the outer ring for rotation about a first horizontal axis, the guide member plate being pivoted on the said inner ring for rotation about a second horizontal axis at right angles to the first horizontal axis, two sets of reciprocating means connected to the guide member shaft for imparting to the guide member oscillatory motion about the first and second horizontal axes respectively, means for controlling the relative rate of reciprocation of the said reciprocating means, to produce the required relative frequencies and relative phases of the oscillations of the guide member about the respective horizontal axes, means for guiding the filament path vertically downwards, from a source at a level above that of the said guide member plate and gimbal mounting arrangement, into the said channel through the guide member, and means for controlling the speed of downward travel of the filament from said source to the carrier.

The said means for controlling the speed of downward travel of the filament preferably includes means for applying impulsion to the downwardly travelling filament as it passes through the channel in the guide member, provided to ensure that the filament passes freely through the channel at the desired speed. Such impulsion is conveniently achieved by means of an arrangement for injecting compressed gas (suitably air) into the guide member channel, from an inlet pipe inserted through the guide member plate, the said arrangement preferably including a venturi structure incorporated within the guide member shaft.

The filament may be delivered to the guiding arrangement and coil carrier from any convenient source, for example from a rotating drum or reel, or directly from a filament manufacturing line, through suitably positioned means for guiding the travel path of the filament into a vertically downward direction. If desired, the filament may, be passed around a motor-driven capstan by means of which its downward rate of travel is controlled, before passing through such guide means.

It will be apparent that a figure of eight coil formed by either of the.methods described above will not have any resultant twist induced in it by the coiling process, since although, in forming each turn of the coil, nearly one full axial twist will be induced in each lobe of the figure of eight, these twists will cancel out as a result of the opposed directions of coiling of the two lobes.

Hence, when the filament is withdrawn from the package by pulling so as to unwind the coil, all the induced twist will be removed so that after withdrawal the filament will possess only the degree of twist, if any, that it had before being packaged: thus, if the filament is free from twist before coiling, when uncoiled and, for example, wound on a drum for use or fed directly into a cable-making system, it will still be twist-free.

The package of the invention is particularly advantageous for the transportatian and storage of optical fibres, both on account of the freedom from resultant induced twist referred to above, and because in a coil formed by either of the methods described the fibre is substantially free from tension: these factors are both desirable for minimising optical losses in the fibre when it is subsequently used for the transmission of telecommunications signals. Furthermore, the absence of tension enables any desired tests or measurements to be carried out on the fibre while it is retained in the coiled condition on the carrier.

In addition, this form of package, in which-the fibre is freely coiled, is not subject to the problems of differential thermal expansion which can arise when a length of optical fibre is wound on a drum or reel, as in the conventional method of packaging. Before being packaged, giass optical fibres are covered with a protective coating and/or jacket of synthetic resin, such as is normally applied during the manufacture of the fibre.

The guiding arrangement employed in carrying out the coiling process should be such that the travel of the filament is not appreciably impeded by friction. The speed at which the coiling can be carried out, which is of course determined by the speed of downward travel of the filament, will depend to some extent upon the form and frictional characteristics of the guide means. The speed of operation will also depend upon the physical properties of the filament, in particular its mass per unit length, stiffness, and surface friction properties, all of which properties affect the inertia of the filament and hence the rapidity with which it can change its direction of angular momentum to effect the counter-directional coiling.

An additional advantage of the filament package of the invention is that it provides for easy withdrawal ofthe filament from the package' by simply pulling the fibre out of the package in a direction approximately at right angles to the plane of the carrier surface on which the coil is laid, a procedure which does not require any power-driven rotation or other movement of the carrier. The form of the coil ensures that the turns thereof remain in the correct sequence and thus cannot become interlinked and tangled during unwinding.

Some specific forms of apparatus, and methods of operation of such apparatus, for forming a figure of eight optical fibre coil, for a package in accordance with the invention, will now be described by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a plan view of one form of guiding arrangement for forming the figure of eight coil by the said first method described above, Figure 2 shows the arrangement of Figure 1 in elevation, Figure 3 is a plan view of a second form of guiding arrangement for forming the coil by the said first method, Figure 4 shows the arrangement of Figure 3 in elevation, Figure 5 shows, in elevation, one form of apparatus for forming the coil by the said second method described above, Figure 6 is a plan view of the filament guiding arrangement and reciprocating means included in the apparatus of Figure 5, Figure 7 is a sectional elevation of the filament guide member of the apparatus of Figure 5, and its gimbal mounting, showing the construction thereof in detail, Figure 8 is a plan view of the filament guiding arrangement shown in Figure 6 with an alternative form of reciprocating means, and Figure 9 is a plan view of the form of the coil produced by means of any of the forms of apparatus shown in Figures 1 to 8.

Like parts in the different figures of the drawings are indicated by the same reference numerals.

Referring to Figures 1 and 2 of the drawings, the optical fibre coil is deposited on a rectangular tray 1, suitably of wood with a covering of antistatic foam on its upper surface, lying on the floor or any suitable horizontal surface 2. A figure of eight structure composed of rings 3, 4 of copper wire is attached to a metal frame 5 by wire struts 6, the frame being supported by legs 7 (only two of which are shown in Figure 2) standing on the surface 2 outside the tray 1, so that the rings are disposed horizontally above the tray. A metal rod 8, mounted ori the frame 5, is placed across the junction between the rings 3, 4, so as to partially close the gap between the rings.Guide members 9, 10 are located respectively within the areas of the rings 3 and 4: these guide members are formed of copper wire, bent into the shape shown, including legs 11, 12 and horizontal portions 13, 14 supporting the curved fibre guiding portions 9, 10. The ends 1 5, 1 6 of the guide members, located adjacent to the rod 8, are at substantially the same horizontal level as the rings, and the free ends 1 7, 18 of the guide members are at a lower level, a portion of each guide member adjacent to the free end extending slightly outside the ring. The legs 11, 12 are mounted on metal discs 19, 20 which are inserted through slots 21, 22 in the tray 1 and are bolted to the surface 2.The slots permit reciprocation of the tray in the horizontal direction orthogonal to the longitudinal axis of the figure of eight structure, without disturbing either the said structure or the guide members 9, 10, and also allow the guide members to be lifted up for removal of the tray on completion of the coiling operation.

It will be understood that the copper employed for the construction of the rings and guide members may be replaced by any suitable ductiie metal.

In operation of the arrangement shown in Figures 1 and 2, a length of optical fibre 23 is continuously fed from a source (not shown) through an eye 24, suitably formed of polytetrafluoroethylene, which is located vertically above but offset from the centre of the figure of eight structure, and which guides the fibre vertically downwards towards the tray and guiding system.

To initiate the coiling process the free end of the fibre, after passing through the eye, is manually urged into one of the rings 3,4 and into contact with the end 15 or 16 of one of the guide members 9, 10, by means of which it is caused to follow a path just inside the respective ring. On completion of the circuit of the first ring, the fibre passes round the free end 25 of the rod 8, through the gap 26 and into the second ring, where it comes into contact with the second guide member 9 or 10 and is thus caused to change its direction of travel and is guided around the second ring.This process is repeated continuously, the fibre rotating alternately clockwise within one ring and anticlockwise within the other ring: the path followed by the fibre, at the level of the rings, to form the first figure of eight turn of the coil, starting in ring 3, is indicated by the broken line with arrows in Figure 1, and the commencement of the downward path of the fibre within the ring 3 is indicated in Figure 2.

In a specific example of the apparatus described above with reference to Figures 1 and 2, used for coiling a silica optical fibre of 120 microns diameter with a protective coating consisting of a single 3 microns thick layer of carbon-loaded polyurethane resin, the area of the tray 1 is approximately 80 cm x 40 cm, the rings 2 and 3 are each 325 mm in diameter and are located 1 55 mm above the tray, and the eye 24 is at a height of 840 mm (this distance is not critical) above the tray, in a position 70 mm offset from the centre of the double ring structure. The fibre is fed through the eye and into the guide system at a linear speed of 35 metres per minute, to produce a coil of the shape shown in Figure 9.The crossover points 27 of the turns occur vertically below the end 25 of the rod 8, and the crossover points can be spread, as shown in Figure 9, by reciprocating the tray in the manner indicated above.

The arrangement shown in Figures 3 and 4 differs from that of Figures 1 and 2 only in the form of the guide members employed in conjunction with the rings 2 and 3. In this case the rod 8 of Figure 1 is omitted, and the guide member located within the area of each ring consists of a curved length of tubing, 28,29 formed of low friction material such as polytetrafluoroethylene, resting on the surface of the tray 1 and supported by a metal rod 30,31 which is attached to a metal disc 32, 33. The discs are shown resting on the surface of the tray, but if desired they may be mounted on members inserted through slots in the tray, as shown in Figures 1 and 2. If desired the tubes 28, 29 may be replaced by strips of polytetrafluoroethylene.

The manner of operation of this arrangement is similar to that described with reference to Figures 1 and 2, the path followed by the fibre being as shown by the arrowed broken line in Figure 3: after travelling ardund and within one of the rings, the fibre is deflected into the other ring by contact with the point of junctions, 34, between the rings, and then further deflected by contact with one of the tubes 28, 29 to change its direction of rotation around the second ring. In a specific example, using an arrangement of the dimensions specified above with referehce.to Figures 1 and 2, 120 microns diameter silica fibre with a single 3 microns thick coat of polyurethane resin can be fed through the system at a linear speed of up to 46 metres per miriute.The coil thus produced is of a similar form to that shown in Figure 9, but with the crossover poirits of the coil turns displaced further from the centre of the figure of eight, as shown by the arrow in Figure 9.

The apparatus shown in Figures 5 and 6 of the drawings includes a horizontally disposed gimbal mounted guide member comprising a metal disc 42 mounted on a shaft 43, with a central channel 44 for the passage of the optical fibre 41 therethrough, terminating in an elongated nozzle outlet 45 for the fibre, at the lower end of the shaft, and an inlet pipe 46 communicating with the channel 44, for the introduction of compressed air into the channel to impel the fibre through the channel at the desired speed. The gimbal mounting arrangement consists of a fixed outer ring 47, a floating inner ring 48 mounted on the outer ring by pivots 49, and pivots 50 by which the guide member disc 42 is mounted on the inner ring 48. This arrangement of pivots enables the guide member to be oscillated about two horizontal axes at right angles to one another.

As shown in Figure 5, an eye 51 is located vertically.above the opening of the channel 44 in the disc 42, for guiding the fibre, which is fed from a motor driven capstan or drum 52, into a vertical downward path before it passes through the guide member The fibre is deposited upon a square tray or board 53, suitably of wood, which may be covered by a layer of plastic foam 54 (Figure 1), or paper.

A reciprocating arrangement for effecting oscillations of the guide member 42, 43 in such a manner that the optical fibre is deposited on the tray in a coil of figure of eight conformation, is shown in Figure 6 and partly in Figure 5 and consists of two rotatable crank arms 55, 56, driven by a motor through gears (not shown) and respectively connected by means of cords or wires 57, 58, passing round guide rolls 59, 60, to projections 61, 62 carried by the guide member shaft 43. The oscillations are further controlled by spring return means 65, 66 connected to projections 63, 64 on the shaft 43, diametrically opposite to projections 61 and 62 respectively (projection 63 is shown in Figure 5 and projection 64 in Figure 7), to provide back tension on the guide member. The operation of crank arm 55 and spring means 65 causes the disc 42 to oscillate about the pivots 50, controlling the transverse dimensions of the figure of eight coil formed by the deposited fibre, and the operation of crank arm 56 and spring means 66 causes the gimbal ring 48 and hence the disc 42 to oscillate about the pivots 49, controlling the longitudinal dimensions of the figure of eight coil. The crank arms 55 and 56 are driven through a gear ratio of 2 :1 , so that two complete transverse oscillations are effected by crank 55 in the same time that one complete longitudinal oscillation is effected by crank 56, the phase relationship between the oscillations being adjusted so that the minima of the transverse oscillations correspond alternately with the maxima and minima of the longitudinal oscillations.By this means the downward path of travel of the fibre on to the tray is rotated around the two lobes of a figure of eight in clockwise and anticlockwise direction respectively.

The sectional elevation of the guide member and gimbal mounting arrangement shown in Figure 7 is drawn on a vertical plane containing the cord 58 and spring return 66 shown in Figure 6, and shows details of the construction of the guide member, which incorporates an air injection gun. The compressed air inlet 46 communicates with a venturi structure 67 within the shaft 43, for effecting acceleration of the passage of the fibre through the channel 44 and nozzle 45.

Throughout the fibre deposition process, the tray 53 is slowly translated in the direction corresponding to the transverse axis of the figure of eight coil, as is indicated by the arrow in Figure 5, to effect transverse displacement of successive turns of the coil. A convenient arrangement for effecting the translation of the tray consists of a toothed belt 68 (Figure 5) cooperating with a strip 69 of similar toothed belt material attached to the underside of the tray, the belt being rotated around rolls 70 driven by a slow speed motor (not shown).

The shape of the fibre coil produced by the apparatus shown in Figures 5, 6 and 7 operated in the manner described, is substantially as shown in Figure 9, each of the crossover points 27 of the coil turns occurring vertically below the position of the outlet of the guide member nozzle 45 at the minima of both the transverse and longitudinal oscillations.

The optimum speed of operation of the apparatus of Figures 5, 6 and 7, that is to say the optimum speed of the fibre feed and frequencies of the oscillations in relation thereto, will depend upon the physical characteristics of the fibre which affect the rapidity with which the counterdirectional coiling can be effected, as indicated above.

In a specific example of the operation of the apparatus described above with reference to Figures 5, 6 and 7, for coiling a silica optical fibre of 120 microns diameters with a protective coating of filled polyurethane resin 15 microns thick, the fibre is fed through the guide member at a rate of 50 metres per minute, and the crank arms 55 and 56 are rotated at speeds of 50 rpm and 25 rpm respectively, giving 50 complete transverse oscillations and 25 complete longitudinal oscillations of the fibre guide member per minute. These operating speeds result in the formation of a figure of eight coil in which the perimeter of each turn is approximately two metres, that is to say one metre in each lobe.

The alternative reciprocating means shown in Figure 8 includes a pair of push-rods, 71 and 72, which are connected to projections carried by the guide member shaft in positions corresponding respectively to projections 63 and 64 (Figures 5 and 7). Thus the push-rod 71 replaces cord 57 and spring means 65 in Figure 6, and push-rod 72 replaces cord 58 and spring means 66 in Figure 6, the push-rods 71 and 72 respectively controlling the transverse and longitudinal dimensions of the figure of eight coil produced. The push-rods are driven by crank arms 73 and 74, which are respectively attached, for rotation, to rolls 75 and 76 connected together by a toothed belt 77. The system is driven by a stepper motor (not shown) via roll 78 and belt 79.The relative frequencies of the transverse and longitudinal oscillations of the guide member are controlled by the relative magnitudes of the diameters of the rolls 75 and 76: to give the required 2:1 ratio of transverse to longitudinal oscillations, the diameter of roll 75 is half that of roll 76. If the system is operated to produce rotation speeds of 50 rpm and 25 rpm for rolls 75 and 76 respectively, with the same phase relationship as that indicated above with reference to Figures 5 and 6, and with the fibre being fed through the guide member at the rate of 50 metres per minute, the size of the coil formed will be the same as that described in the above specific example with reference tdfigures 5, 6 and 7, the shape of the coil being substantially as shown in Figure 9.The speed of rotation of the roll/belt system in relation to the rate of feed of the fibre may be suitably controlled by electronic means, which may be of known form and is not included in the drawings.

The particular phase relationship between the transverse and longitudinal oscillations referred to above with reference to Figures 5 to 8 is applicable to the coiling of the type of optical fibre described in the above specific example. However, it is to be understood that in some cases, depending on the physical characteristics of the filament, it will be desirable to employ a displaced phase relationship, in order to avoid undue distortion of the figure of eight coil produced. For example, for coiling an optical fibre having high mass per unit length or having a soft coating such as a silicone resin, it may be desirable to advance the phase of the transverse oscillations by up to 450 in relation to the longitudinal oscillations.

The fibre can readily be withdrawn from a package formed by any of the processes described above with reference to the drawings, and, for example, wound on to a drum, by placing the tray carrying the coil in such a position that the centre of the figure of eight coil is vertically below a guiding eye similar to the eye 24 in Figures 2 and 4, or 51 in Figure 5, threading the free end of the fibre through the eye and winding a turn or two round the drum, then rotating the drum, while the tray is kept stationary.

Claims (20)

1. A filament package consisting of one or more lengths of filament lying loosely coiled on a plane surface of a flat carrier and covered with a layer of padding material, the carrier being integral with or inserted into a shallow container in which the assembly of carrier, filament coil or coils and padding is enclosed, wherein the coil, or each coil, is composed of two lobes together forming substantially a figure of eight, as hereinbefore defined, and consists of a multiplicity of turns, each of which is laid in said two lobes, the filament forming one lobe of each turn being laid in a clockwise direction, and the filament forming the other lobe of each turn being laid in an anticlockwise direction.

2. A filament package according to Claim 1, wherein the crossover point between the lobes of the second and each successive figure of eight turn of the coil is displaced from the preceding crossover point in a direction orthogonal to the longitudinal axis of the figure of eight and in the plane of the respective turn of the coil.

3. A process for forming a filament coil of substantially figure of eight conformation, in the production of a filament package according to Claim 1 or 2, which consists in feeding a length of filament continuously downwards, at a controlled speed, on to the upper plane surface of a horizontally disposed carrier, through a guiding arrangement whereby, for the deposition of each figure of eight turn of the coil on the carrier, the downward path of travel of the filament is caused to rotate in a clockwise direction to describe a first lobe of a figure of eight and in an anticlockwise direction to describe a second lobe of a figure of eight, such clockwise and anticlockwise rotations being effected alternately during the deposition of the whole length of filament.

4. A process according to Claim 3, wherein the filament is fed downwards through a horizontally disposed figure of eight shaped structure having a gap in the junction of the two lobes of the figures of eight, and the downward path of travel of the filament is caused, by stationary guide means cooperating with the figure of eight structure, to rotate alternately within one lobe of the said structure in a clockwise direction and within the other lobe of said structure in an anticlockwise direction.

5. A process according to Claim 3, wherein the filament is fed downwards through a gimbal mounted guide member while the said member is caused, by means of the gimbal mounting, to oscillate about two horizontal axes at right angles to one another, the relative frequencies and relative phases of the oscillations about the respective axes being so controlled that the downward path of travel of the filament between said guide member and the carrier describes a figure of eight whose longitudinal and transverse axes lie parallel to the respective axes of oscillation of the said member.

6. A process according to Claim 3,4 or 5, wherein displacement of the crossover points between the lobes of successive figure of eight turns of the coil is effected by translation or reciprocation of the carrier in the horizontal direction orthogonal to the longitudinal axis of the coil, while the filament guiding arrangement is maintained in a constant location.

7. Apparatus for forming a filament coil by the process according to Claim 4, which includes a figure of eight shaped structure, horizontally disposed above the fialment receiving carrier, which structure is formed of two rings meeting substantially tangentially but with a gap in the junction between the rings, means for guiding the filament path vertically downwards from a source at a level above that of the said rings to a point in the vicinity of the junction between the rings, and guide means co-operating with the rings to cause the further downward path of travel of the filament to rotate alternately within one ring in a clockwise direction and within the other ring in an anticlockwise direction.

8. Apparatus according to Claim 7, wherein the said rings are of equal diameter, so that the two lobes of each figure of eight turn of the coil formed are of substantially equal area, and the coil produced is symmetrical about the junction between the lobes of the figure of eight.

9. Apparatus according to Claim 7 or 8, wherein the said guide means co-operating with the rings includes a pair of guide members located respectively within, and at the level of and/or below, the two rings, and at least partly adjacent to the said gap, each said guide member being so positioned, in relation to the width of said gap, that said member is contacted by the filament immediately after the filament has passed through the gap, and each said guide member being shaped so as to deflect the filament into a path of travel rotating in the direction opposite to that which it previously followed, and closely adjacent to the ring.

10. Apparatus for forming a filament coil by the process according to Claim 5, which includes a filament guide member consisting of a plate horizontally disposed above the filament receiving carrier and mounted on a vertical shaft, with a central channel through the plate and shaft for the passage of the filament downwards therethrough, a gimbal mounting arrangement for said guide member consisting of a fixed horizontally disposed outer ring and an inner ring pivoted on the outer ring for rotation about a first horizontal axis, the guide member plate being pivoted on the said inner ring for rotation about a second horizontal axis at right angles to the first horizontal axis, two sets of reciprocating means connected to the guide member shaft for imparting to the guide member oscillatory motion about the first and second horizontal axes respectively, means for controlling the relative rates of reciprocation of the said reciprocating means, to produce the required relative frequencies and relative phases of the oscillations of the guide member about the respective horizontal axes, means for guiding the filament path vertically downwards, from a source at a level above that of the said guide member plate and gimbal mounting arrangement, into the said channel through the guide member, and means for controlling the speed of downward travel of the filament from the said source to the carrier.

11. Apparatus according to Claim 10, wherein the said means for controlling the speed of downward travel of the filament includes means for applying impulsion to the filament as it passes through the channel in the guide member.

12. Apparatus according to Claim 11, wherein the said means for applying impulsion to the filament consists of an arrangement for injecting compressed gas into the guide member channel, from an inlet pipe inserted through the guide member plate.

13. Apparatus according to Claim 12, wherein the said gas injection arrangement includes a venturi structure incorporated within the guide member shaft.

14. Apparatus according to Claim 10, 11, 12 or 13, which includes a motor-driven capstan around which the filament from said source is passed, said means for guiding the filament path vertically downwards being located between the capstan and the guide member plate.

1 5. Apparatus according to Claim 7, substantially as shown in, and as hereinbefore described with reference to, Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.

1 6. A process according to Claim 4 for forming an optical fibre coil of substantially figure of eight conformation, substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4, and Figure 9, of the accompanying drawings.

1 7. Apparatus according to Claim 10, substantially as shown in, and as hereinbefore described with reference to, Figures 5, 6 and 7 of the accompanying drawings.

18. Apparatus according to Claim 17, with the modification shown in, and hereinbefore described with reference to, Figure 8 of the accompanying drawings.

1 9. A process according to Claim 5 for forming an optical fibre coil of substantially figure of eight conformation, substantially as hereinbefore described with reference to Figures 5, 6, 7, 8 and 9 of the accompanying drawings.

20. A filament coil of substantially figure of eight conformation, which has been produced by a process according to any of the preceding Claims 3to6, 16or 19.