GB2064808A

GB2064808A - Process and apparatus for the production of optical fibre cables

Info

Publication number: GB2064808A
Application number: GB8034365A
Authority: GB
Original assignee: FOPTICA
Current assignee: FOPTICA
Priority date: 1979-12-06
Filing date: 1980-10-24
Publication date: 1981-06-17
Also published as: DE3045713A1; FR2470979B1; DE3045713C2; FR2470979A1

Abstract

A process and apparatus is described for the manufacture of fibre optic cables comprising a central support member 21 having a plurality of helical grooves 23 in the surface thereof each of which accommodates a fibre optic 27. 0ptionally the assembly is enclosed in an outer sheath. According to the invention the groove 23 is cut in the surface of the support member 21 by cutting tools 24 as the support member advances in the direction A. The fibre optic 27 is then laid in the groove at a point N4 which is at a fixed angular and linear distance from the cutting point N. During advancement the support member is rotated about its axis relative to the cutting tool thereby to form a helical groove. <IMAGE>

Description

SPECIFICATION Process and apparatus for the production of optical fibre cables The present invention concerns a process for the production of optical fibre cables comprising a central or reed member which is provided at its surface with helicoidal grooves, each being intended to receive at least one optical fibre, the assembly comprising the central or reed member and the optical fibres set in position thereon being surrounded by means for fixing the fibres in the grooves.

The invention also concerns an installation for carrying out such a process.

Various processes and installations for the production of such optical fibre cables are already known. A known example of such a cable and the installation for the production thereof will be described hereinafter.

Fig. 1 shows the main part of the cable, that is to say, a central or reed member 1 which may be provided with a core 2. At its surface, the member 1 comprises grooves 3, 4, 5 and 6, each receiving an optical fibre 7, 8, 9 and 10. The fibres are held in place in the grooves 3 to 6 by a wire 11 or braiding or strip winding or sheathing, which is disposed around the member 1.

Fig. 1 shows that the optical fibres 7 to 10 are of very small section compared to the section of the grooves 3 to 6 so that no stress is transmitted by the member 1 and the core 2 to the optical fibres 7 to 10 as any mechanical stress damages the physical characteristics of the optical fibres.

The cable is surrounded by one or more external protective sheaths which are not shown in Fig. 1.

The problem which arises in production of an optical fibre cable of this kind is for the fibres to be correctly disposed in the housing grooves, bearing in mind the extremely small dimensions of the assembly comprising the reed member 1 and the fibres.

In fact, the grooves 3 to 6 which, in Fig. 1, are of semicircular section, are of the order of from 0.25 to 0.75 mm in diameter while the fibres 7 to 10 are of the order of from 0.1 to 0.35 mm or more in diameter.

Moreover, the handling operations which are performed on the optical fibres are very delicate as the fibres can easily be broken.

In conclusion, in production of such a cable, it is necessary at all costs to avoid a fibre 7 to 10 being positioned outside of its groove, even if that should be over a very short length, as the strip or fixing means 11 would jam the fibre against the outside surface of the member 1. The sheath would complete the jamming action so that all the mechanical tensile forces to which the member 1 and its core 2 are subjected would have repercussions on the corresponding optical fibre and would make it unusable. Even more, in the event of such a production defect, it is not just the fibre concerned which becomes useless, but the whole of the cable, which gives rise to very substantial losses.

Various installations for producing such cables are already known.

As it is necessary to operate to a very high degree of accuracy, the present installations are extremely complex and heavy.

Fig. 2 shows a possible diagram of such an installation.

In the known process and installation, the central or reed member is produced by extrusion by means of a die and suitable means for producing the helicoidal line of the grooves.

After cooling, the central member is wound on to spools so as to be passed into the station for setting the optical fibres in place.

Such a station is shown in Fig. 2. It comprises a feed spool 1 2 which supplies the central or reed member 13, passing it over direction-changing pulleys 14, to pass through the rotary plate 15, into the detector 16, into a sheathing station 17, etc, then over the direction-changing pulley 18, for winding on a spool.

The installation is extremely complex and heavy as the plate 1 5 carries spools 151, 1 52 and 1 53 (their number corresponds to the number of optical fibres to be set in place), which each provide a fibre which will be deposited in the grooves of the central member 13 by the head 19.

The detector 16, which may be at any position on the path of movement of the central or reed member between the pulleys 14 and 1 8, detects the position of the grooves so as to control the control circuit 20 which controls the rotary motion of the assembly comprising the plate 15, including the members 151-153 and 19, so as to bring the points (not shown) at which the optical fibres are deposited into coincidence with the corresponding position of the grooves in the member 1 3.

The complexity of the above-described installation results from the disproportion between the extremely small dimensions of the central members and the grooves and the very substantial dimensions of the plate 1 5 and the various components carried thereby. Indeed, and by way of example, such a plate may be several metres (2 to 5 metres) in diameter.

The very substantial size of the plate 1 5 carrying the feed spools 151 to 153 is made necessary by the size of the spools of fibre and by the complexity of the feed in respect of the optical fibres, means which are absolutely necessary for controlling the tension of the optical fibres, and so on.

There is no way in the known installations in which the control action in respect of the plate 1 5 can be suppressed as the position of the grooves varies continuously during the movement of the member 1 3 through the plate. It would also be illusory to mark the initial position of the grooves when the installation is started up, and then to control the speed of movement of the cable and the speed of rotation of the plate in order thereby to maintain the condition of coincidence between the instantaneous position of the fibre depositing heads and the position of the grooves in the central member.Such a solution cannot be envisaged in practice because of the very small dimensions of the grooves and the fibres, the fragility of the fibres which does not allow substantial pulling forces to be applied thereto, the danger of depositing a fibre beside its actual groove, even at a very short distance therefrom, etc.

The aim of the present invention is to provide a process and an installation for the production of optical cables having a central or reed member provided with helicoidal grooves for receiving the optical fibres, which process and installation are to be simpler and more reliable than the known processes and installations.

For this purpose, the present invention concerns a process for the production of an optical fibre cable comprising a reed member provided at its periphery with helocoidal grooves containing optical fibres the assembly being surrounded by a sheath, characterised n that: - a reed member with a smooth outer surface is made, - a pitch for the helicoidal grooves is selected, - a relative translatory and rotary movement is produced between the reed member and a machining tool for cutting a helicoidal groove in the reed member, - an optical fibre is deposited in the helicoiual groove at a fixed point with respect to the point ot engagement ot the tool on the reed member, said fixed poim being determined geometncaliy with respect to the point of engagement of the tool in dependence on the selected pitch of the nellcoidal groove.

As, in this process, the optical fibres are positioned solely in dependence on the position of the tools forming the helicoidal grooves in the reed member, this process does not require any delicate and complex operation tor detecting the helicoidal grooves.

This simplifies the process and makes it much more reliable and inexpensive than the known process.

The invention also concerns an installation for carrying out the process, the instaliation oeing characteriseo in tnat it comprises means for proaucing at least one groove in the reed member upstream of the fibre depositing means, said groove-producing means being disposed at a fixed adjustabie longitudinal and angular position relative to the position of the fibre depositing means, anu upstream ol said latter position.

This therefore avoids the use of any detection head and any control action in respect of the position of the means for depositing the optical fibres in the helicoidal grooves.

In accordance with a feature which is particularly attractive from the point of view of construction of the machine, the means for producing a groove is a tool which is fixed with respect to the fibre depositing means and, the resulting assembly being displaced with a constant relative rotary movement about the central member which is entrained at a constant iinear speed, the supply means and the receiving means are fixed in respect of relative rotary movement about the line X-X of movement of the central member. In a particular embodiment, the supply and receiving means are driven in rotation about that line during the movement of the central member, the means for producing the groove or grooves and the fibre depositing means being fixed.In such a construction, the tools and the depositing means are effectively moved with a relative rotary movement around the central member.

The present invention will now be described in greater detail with reference to the accompanying drawings in which: Figure 1 is a perspective view on a greatly enlarged scale of the main part of an optical fibre cable, Figure 2 is a diagrammatic view of a known installation for producing optical fibre cables, Figure 3 is a view on an enlarged scale for describing the process of the invention, Figure 3A is a diagrammatic sectional view of a central or reed member showing the angular displacement of a fibre depositing point with respect to the point of production of the groove, Figure 4 is a highly diagrammatic view of a first embodiment of the invention, Figure 5 is a diagrammatic view of a sec onci embodiment of an installation according tG the invention, Figures 6A-6E show diagrammatic views of various alternative embodiments of the invention, and Figure 7 is a view in partial section of a member for depositing optical fibres in a groove.

According to the invention, the process for the production of cables having optical fibres which are positioned in the helicoidal grooves in a central or reed member comprises producing a central or reed member which may possibly be armoured but whose outside sur ace does not comprise any groove, then passing the centrai or reed member into a fibre depositing head so as to have both a relative translatory movement and a relative rotary movement as between the fibre deposit ng head and the central member. in fact, during such movement, the fibre depositing head which comprises both the tools and, at a downstream position, the means for depositing the fibres at a given longitudinal and angular spacing, forms the grooves and deposits the fibres therein.As the axial distance which separates each tool forming a groove and the head for depositing the corresponding fibre in the groove which has just been made is known, it is easy to set the angular displacement between the tool which cuts the groove and the tool which deposits the fibre, in order thereby not to necessitate any interdependent positional control between the two tools.

In Fig. 3, which is used to describe this process, the pitch of the grooves has been deliberately reduced so as to be able to draw a number of turns on a reed or central member of substantial diameter.

Fig. 3 shows a central or reed member 21 in which two helicoidal grooves 22 and 23 have been produced by means of the process of the invention. According to the invention, the member 21 is advanced in the direction indicated by arrow A, while being rotated about its axis X-X, as indicated by arrow B.

There is provided a fixed apparatus which, diagrammatically, comprises a tool 24 for cutting the groove 23, and a fibre supply means 25 for the member 26 which serves to deposit an optical fibre 27 in the groove 23 at point N4. The components 24, 25 and 26 are mounted on the same frame structure and are fixed with respect to each other. Thus, the position N4 of the depositing member 26 is at a distance H4 (in the longitudinal direction) and at an angularly offset position as indicated by 84 (about the line X-X), which are determined with respect to the point N (see Figs. 3 and 3A).

In fact, as the pitch H of the helicoidal groove 31 is pre-selected, H4 is linked to the angle 84 by the following relationship: O4 H4 = H.

2r The selection in respect of the angle 84 depends solely on the capabilities in regard to positioning and size of the tools and components 24, 25 and 26 in the space around the member 1.

As the position of the point N4 is known and depends solely on the installation and not the member 1, it is possible for the point N4 to be displaced over several lengths of pitch H.

Fig. 3 shows by way of example various points N1, N2, N3,N4, N5 and N6 which can be selected for positioning the depositing member 202. Indeed, any points which are disposed downstream of th point N in the direction of movement A of the central or reed member 21 can be used.

By way of example, the drawing shows similar points for the groove 22, which is cut at point P. The position of the tool 241 which produces the groove 22 is selected, with respect to the position of the point N, so as to achieve suitable distribution of the grooves.

The groove distribution may be regular or irregular in a plane perpendicular to the line X-X, depending on the nature of the fibres, the number thereof, etc.

The point P and the other points (not shown) at which the different grooves are formed are in a given geometrical position with respect to the point N. This however does not mean that all the points N, P .

must necessarily be disposed in the same plane perpendicular to the line X-X. Similarly, as was shown in regard to point N4, it is possible for points P . . . to be located in other cutting planes than point N, for example upstream or downstream of that plane, in the direction of movement A of the central member 21. Just as any point N1, N2 . . . of the groove 23 could be associated with point N, it is also possible for any point of groove 22, that is to say, P1, P2, P3 . . . to be associated with point P; the points P1, P2, P3 which . . while are only given by way of example, it being appreciated that, since the pitch of the grooves 23, 22 .. must be the same in order for the grooves not to intersect each other, it must necessarily be that, taking into account the relative angular position as between a point P and for example a point P1 which is angularly displaced through angle a1 with respect to point P, the axial distance 1, between point P1 and point P is equal to: cwl i1 = H.

2rr In conclusion, in the process of the invention, the pitch H of the helicoidal grooves is first fixed, and then the central or reed member is passed at a certain speed, while causing it to rotate around itself about its axis X-X, at a corresponding speed for producing the desired pitch. The points of engagement of the tools for forming the grooves 23, 22. . for receiving the optical fibres 27 . . . occupy a fixed position and the position of the optical fibre depositing members 26 . . is fixed and determined with respect to the position N, P of . . or the members for forming the helicoidal grooves.

The movement of the central member 21 in the longitudinal direction A and in rotation as indicated by B about its centreline X-X is a relative movement with respect to the points N, M, P1 .... All combinations of movement as between the central member 1 and the tools 24, 25 and 26, as produced by the points N, P, N4, P1 . . are possible. Thus, the central or reed member can be fed in the direction indicated by arrow A without causing it to rotate about its centreline but by rotating the tools 24, 25, 26 . . . in the direction B' which is opposite to the direction B, about the line X-X. Among all the possible combinations of relative speeds as between the central or reed member 21 and the members 24, 25 and 26, only those indicated above are of practical interest.

The construction of an installation for carrying out the process of the invention, as shown in Fig. 4, corresponds to the second design, that is to say, longitudinal movement of the central or reed member or the cable along its centreline and rotation of the members for cutting the groove and depositing the optical fibres, in direction B' opposite to direction B.

The second embodiment shown in Figs. 5 and 6 provides for leaving the groove cutting and fibre depositing members stationary in space and feeding the central or reed member in the direction indicated by arrow A, while also rotating it about itself in the direction indicated by arrow B, about its centreline, between a supply station and a receiving station.

In the first embodiment (Fig. 4), the installation comprises a supply station 28 for providing a reed or central member 29 which does not have any groove. The member 29 is formed by a simple extrusion operation by means of a smooth die.The reed 29 passes over a direction-changing pulley 30 in order to pass into the machine and issues therefrom around pulley 106. The path between the pulley 102 and the pulley 106 defines the above-indicated line X-X. Disposed on the path X-X is a table 31 carrying optical fibre supply spools 32 and a head 33 which is provided with tools for cutting grooves and members for depositing fibres, as shown in Fig 3. The relative position as between the groove cutting tools and the optical fibre depositing members are fixed positions in the head 33. The head 33 rotates integrally with the plate 31.The head 33 and the plate 31 do not require any detection in respect of the grooves or any control in respect of their rotary movement in dependence on detection signals.The only determining factors are the speed of movement in the direction A and the speed of rotation in direction B' to ensure that the helicoidal grooves are at the appropriate pitch.

The speed of rotation and the speed of linear movement must be correctly regulated in order to produce a regular product. However. this is not a disadvantage as the regulation ac.tion is effected by setting up a predetermined reference control speed and not by detection of a variable parameter and dependent control of a speed (linear or in rotation, depending on the detection operation). A particularly simple solution comprises synchronising the two movements rigidly, either by sets of gears or belts or any other suitable means. In practice, in the case of the installation shown in Fig. 5, the position of the turns produced by the cutting tools is fixed in space, so that the resulting turns also appear to be fixed in space. In contrast, in a known installation like that shown in Fig. 2, the turns are displaced in space.

Fig. 5 is a highly diagrammatic perspective view of the main part of a machine for the production of cables having a plurality of optical fibres, in accordance with the abovedescribed process.

In this machine, the cable is moved linearly while being rotated.

The various parts of the machine such as the frame structure, casings, etc have been deliberately omitted for the sake of simplicity of the drawing, so Fig. 5 is limited to the parts which are disposed aroung the centreline X-X along which the cable moves in the direction indicated by arrow A, while rotating about itself in the direction indicated by arrow B.

In greater detail now, the machine comprises a reed member supply means formed by a feed spool 34 on which a reserve of central reed member 35 is wound, and a receiving means formed by a receiving spool 36 which receives the cable in the condition of a finished or semi-finished product, at the exit from the machine.

Each spool 34 and 36 is carried by a respective stirrup-like bracket member 37 and 38 which removably carries its respective spool so as to permit a fresh spool 34 to be set in place and to permit the spool 36 carrying the finished cable to be removed.

The member 37 is fixed with respect to a hub 39 which is housed in a bearing 40. The hub 39 also carries a drive pulley 41.

There is a similar arrangement in respect of the receiving member 38 which is provided with a hub 42 housed in a bearing 43; the hub 42 carries a pulley 44. The supply means and the receiving means are driven in rotation in the direction indicated by arrow B, about the centreline X-X. The speed of rotation of the two means is strictly identical so as not to induce any twist in the central or reed member or the cable which moves along the line X-X between the supply means and the receiving means.

Disposed parallel with respect to the centreline X-X is the transmission shaft 45, on centreline Y-Y. The shaft 45 non-rotatably carries thereon various pulleys which will be further described hereinafter and which provide for transmission of the rotary movement of the shaft 45 to various members mounted along the line X-X. The shaft 45 also carries a pulley 46 which is driven by a belt 47 from the output pulley 48 of the motor 49. The belt 47 and all the other belts of the installation are belts which provide for synchronous transmission of the movement of the shaft 45, without slip.

Facing the pulley 41, the shaft 45 carries a pulley 50 which transmits its movement by way of the belt 51. Close to the exit from the machine, the shaft 45 also carries a pulley 52 which transmits the rotary movement of the shaft 45 to the pulley 44 by way of the belt 53.

As the pulleys 41 and 44 are respectively fixed with respect to the hubs 39 and 42, the movement of the shaft 45 is transmitted to the members 37 and 38 which thus produce a rotary movement of the cable 35, about its centreline X-X, while providing for linear movement thereof in the direction indicated by arrow A.

Downstream of the supply means formed by the members 34, 37, 39 and 41, there is a drive means 54 which receives its movement from the pulley 55 which is driven by the bolt 56 from the pulley 57 which is fixed on the shaft 45. The drawing does not show details of the means for transmitting the movement between the pulley 55 and the drive means 54. It may involve slip-free belts or a differential mechanism.

The drive device 54 comprises for example two conveyor belts 57 and 58 which pass over pulleys 59 disposed on respective sides of the line X-X so as to trap the central or reed member 35 between the directly facing faces of the conveyor belts 54 and 57.

The drive device 54 preferably comprises two conveyor belts, as described above, so as properly to hold the member 35 both in a translatory respect and in a rotary respect.

As indicated above, the drive movement of the pulley 55 is transmitted to the drive device 54 by a transmission means such as a differential, not shown, as this type of means is known. Means other than conveyor belts may be envisaged, such as rollers which provide for good angular stability of the central or reed member, until close to the machining means 60.

In the diagrammatic view in Fig. 5, said means comprises four tools 61 which are at an angle of 90t relative to each other. The tools which are shown on an highly enlarged scale relative to the central member are intended to form the helicoidal grooves in the surface of the central member. The tools 61 are fixed both in regard to rotary movement and in regard to lranslatory movement, relative to the machine. The tools 61 of the machining means 60 are carrid by carriages (not shown) controlled by micrometric screws which permit regulation of the depth of cut and the position of the groove. The cutting means 60 is disposed downstream of the drive means 54 and in the immediate vicinity thereof.

The tools of the machining means 60 are preferably cutting tools which cut a groove into the surface of the member 35 along a path which depends on the translatory and rotary movement of the member 35 with respect to the tools 61. However, this embodiment of the tools is not the only one as it is possible to envisage tools which operate by a fusion action, electro-erosion, etc.

A second drive means 62 may optionally be disposed downstream of the machining means 60 and may also comprise two conveyor belts 63 and 64 passing over pulleys 65 and 66.

As for the drive means 54, the means 62 is driven by pulley 67 which is fixed on the shaft 45 and which transmits its movement by way of the belt 68.

The drive means 54 and 62, upstream and downstream of the machining means 60, are very important components for correctly holding the member 35 during its translatory and rotary movement relative to the tools 61.

The tools 61 of the machining means 60 are shown in the same plane perpendicular to the line X-X. However, as indicated hereinbefore in the general statement relating to the invention, such tools can be displaced along the line X-X, depending on the space problems encountered.

The angular orientation of the tools about the line X-X is fixed and may a priori be any orientation.

The downstream drive means 62 provides the traction force for the member 35, for cutting the helicoidal grooves in the member 35.

The fibre depositing means 69 which is disposed downstream of the machining means 60 comprises four depositing members 70 which are shown diagrammatically in the form of rollers having their axes substantially perpendicular to the direction of the line X-X; the rollers 70 are each disposed in a plane forming a dihedron with the plane defined by the centre of symmetry 0 of the roller and the line X-X. The edge of the dihedron is the perpendicular dropped from 0 to X-X. The angle of the dihedron is equal to the angle formed by the helicoidal grooves with the generating lines of the central or reed member.

As indicated above, the angular position of the rollers 70 about the line X-X depends on the one hand on the angular position of the tools 61 of the machining means 60 and on the other hand on the axial distance between the tools 61 and the rollers 70, depending on the selected pitch of the helicoidal grooves produced in the member 35 by the tools 61.

The fibres 71A which arrive at the rollers 70 of the fibre depositing means 69 pass over pulleys 71 from a supply means (not shown).

an embodiment of a depositing roller 70 will be described hereinafter with reference to Fig.

7. Each depositing member 70 is provided with micrometric means permitting control of the depth of penetration into the grooves; as indicated above, the angle of the means 69 is set with respect to the line X-X so as to be adapted to the pitches selected for the helicoidal grooves. The condition of coincidence as between the members 70 and the position of the helicoidal grooves is achieved by rotating the means 60 through a suitable angle about the line X-X, as it is advantageous for the fibre supply means (not shown) and the direction-changing pulleys 71 and the means 60 to be in a fixed position.

It will be appreciated that the number of tools is limited only by the use envisaged or by problems concerned with materials and the amount of space occupied.

A similar consideration applies in regard to the number of members 70 which is generally equal to the number of tools 61.

Disposed downstream of the means 69 is the strip winding station 72 which is not described in detail; the arrangement 72 is driven in rotation about centreline X-X at a speed which is a precise multiple of the speed of rotation of the member 35 about the centreline X-X, in order to produce precise and constant winding. For that purpose, the arrangement 72 is driven from the common shaft 45 by way of the pulley 73, the belt 74, a step-down ratio box 75, a pulley 76, a belt 77 and finally a pulley 78 which is fixed with respect to the winding arrangement 79 proper.

Irrespective of the fact that, in theory, the position of the grooves is fixed in space since all the arrangements and members rotate at the same speed of rotation and in the same direction B about the centreline X-X of the machine, it is possible in some cases to observe a slight angular fluctuation in the grooves. This fluctuation is due to the elasticity in respect of torsional stress in the central or reed member, produced under the effect of the tangential forces by the winding head.

These various twisting phenomena cannot be cumulative but they are troublesome.

Therefore, disposed between the arrangement 72 and the depositing means 69 is a stop means 80 for preventing transmission of a couple from downstream of the means 80 in an upstream direction towards the means 69.

The stop means 80 comprises two rollers 81 having their axes perpendicular to the line X-X. The two rollers are freely rotatable about their axes. The assembly formed by the rollers 81 and their carrier arrangement (not shown) is driven in rotation about the line X-X by way of the pulley 82 which itself is driven by the belt 83 and the pulley 84 from the common shaft 45.

The transmission ratio between the pulleys 82 and 84 is equal to the general ratio between the pulleys mounted on the centreline X-X and those mounted on the line Y-Y so that the rollers 81 rotate synchronously with the reed member 1 without leading or trailing, in order to prevent the transmission of any twisting force or couple which is induced in the central or reed member at the winding arrangement 72.

Downstream of the winding arrangement 72 is a control device 85 for controlling the tension of the cable produced upstream thereof. The control device 85 is formed by a frame 86 carrying a pulley 87 which receives the movement of the shaft 45 by way of a pulley 88 and a belt 89. As the pulleys 88 and 87 are in a suitable ratio to each other, the device 85 rotates synchronously with the central or reed member 35. The device 85 comprises a drive capstan 90 and a driven capstan 91. The cable forms several turns around the capstans 90 and 91, leaving the general centreline X-X of movement so as to pass firstly around the capstan 90, leaving the capstan 91 to return to the line X-X and pass on to the receiving spool 36 of the receiving arrangement.

In the device 85 which rotates synchronously with the machine, the central member provided with the optical fibres performs several turns at a strictly determined peripheral speed so that the central member receives a strictly controlled tension while it is on the capstan. The peripheral speed is referenced on the speed of rotation of the shaft 45 by way of a differential mechanism or a set of gears or reducing means (not shown).

The receiving means which is disposed outside of the machine is substantially identical to the supply means at the entry to the machine. Nonetheless, on the line of movement of the cable along the centreline X-X, the receiving means comprises a spool winding means 92 formed by pulleys or cylinders 93 to ensure that the cable is regularly wound on to the spool 36.

Fig. 6A shows a simplified diagrammatic view of the Fig. 5 arrangement.

Fig. 6B is an alternative form of the embodiment of the Figs. 5 and 6A, in that the means 54 and 62 are replaced by capstans 54' and 62', the other components being identical.

The embodiment shown in Fig. 6C differs from that shown in Fig. 6A in that the depositing means 69 immediately follows the machining means 62 without the interposition of a drive means like the means 62. The other components of this embodiment are identical.

The embodiment of Fig. 6D corresponds to that shown in Fig. 6C except that the two conveyor belts of the means 54 are replaced by a capstan-type means 54", the other components being identical.

Fig. 6E shows a preferred embodiment wherein the conveying and pulling means 62 is disposed between the winding station 72 and the capstan 85. At that point, it absorbs all the random tensions induced by the machining operation and the winding operation and the fibres still slide very freely in their grooves. They therefore are not subjected to disorderly extension phenomena resulting from such tensile forces. A defined force giving a defined elongation effect can be instralled and controlled between the means 62 and the means 85.

Fig. 7 is a view in partial section of a means for depositing a fibre in a groove.

The means 70 serves to deposit the fibre 100 in the helicoidal groove 101 provided in the member 35.

The means 70 essentially comprises a guide casing 102 in the form of two half-shells which are cut in a central plane. The casing 102 terminates in a projection 103, the forward end of which is at a spacing less than the mouth of the groove 101. The half-shells 102 of the casing enclose a roller which is freely rotatable on a shaft 104 by way of a ball rolling bearing assembly 105. The roller comprises a hub member 106 provided with a removable portion 107 secured in position by a screw 108a. The part of the hub portion 106 has a double shoulder as at 1 06a and 106 b.The removable portion 107 is of complementary shape to that of the recess defining the shoulder 1 06a and the recess defining the shoulder 106b, so as to permit movement in the direction of the doubleheaded arrow C when the screw 108a is unscrewed, to remove the annular portion 107. In this way it is possible to gain access to a ring member 108 which is preferably non-rotatably fixed to the hub portion 106 when the screw 1 08a is tightened. The ring member 108 is trapped between the shoulder 106aand the portion 107.

The outside surface of the ring member 108 which is intended to come into contact wit the optical fibre 100 has a slightly curved concave surface 109.

The diameter of the outside surface of the ring member 108 relative to the centreline Z-Z of the shaft 104 is less than the length L of the end of the casing 102, to form a housing 109 which is open forwardly and which forms a guide groove for the wire 1 00.

The roller which is formed by the hub portion 106, the removable portion 107 and the ring member 108 and which is freely rotatable about the shaft 104 by way of the ball bearing assemblies 105 is an essential feature of the invention. In fact, it is absolutely essential for the optical fibre 100 to be deposited without rubbing and without stress in the groove, which is made possible in particular by the roller.

Generally, the machine according to the invention comprises speed and tension control circuits and safety and monitoring control circuits for running the machine. These various means are not shown.

Among the monitoring means, the machine comprises in particular monitoring means for detecting rupture of the optical fibres or blocking thereof with stresses (which substantially reduces the light-transparency thereof). Such monitoring means comprise a light source which is disposed at the end of each optical fibre which is on the supply spool (not shown) of the depositing device 69 and moreover at the corresponding end of the fibre of the finished cable, on the spool 36, or vice-versa.

In the event of a break in the transmission of light, the arrangement causes the machine to stop. It is then possible to remedy this problem, whether it involves an optical fibre being jammed with stresses outside of the groove, or rupture of an optical fibre.

In the various alternative forms described above, according to circumstances, it may be necessary to provide a drive arrangement 62 and 62' downstream of the machining means 60.

This arrangement then supplies the drive force required for machining the central or reed member. This force applies a tension to the reed member and causes elongation thereof, which depends only on the opposing force produced by the machining means.

Such elongation is not necessarily equal to that which must be imparted to the central or reed member in order to produce the overlength of fibre required. The arrangement 62 isolates the machining operation and the aftereffects thereof. After the arrangement 62, it is possible to apply a given traction force to the central or reed member, which is independent of the machining force. As indicated above, the arrangement 6E is preferable.

Indeed, the arrangement 62 provides for the general forward movement of the central member. In some cases, when there is no drive arrangement 62 and 62' (in particular in Figs. 6 and 6D), the means 85 provided at the exit from the machine provides for drive for the cable through the machine.

Finally, and as already indicated above, all the various rotating components must rotate in strict synchronisation. This is partly shown in diagrammatic form in Fig. 5 in which the corresponding pulleys which are mounted on the one hand on the shaft 45 and on the other hand about the centreline X-X, have the same ratio between diameters. Moreover, in order to ensure perfect rotational synchronisation, the belts 83 are T-belts. Other means could be envisaged.

Claims

1. A process for the production of an optical fibre cable of the type comprising an inner support member formed on its surface with a plurality of helical grooves each accommodating an optical fibre, which comprises advancing a preformed, ungrooved support member through a cutting station comprising a plurality of cutting means operable to form a plurality of grooves in the surface of the support member as it passes through the cutting station, laying an optical fibre into each of said grooves at a point which is at a fixed angular and linear distance from point at which the respective groove is formed, and rotating the support member relative to the cutting means as it passes through the cutting station thereby to produce in the surface of the support member helical grooves having a predetermined pitch dependent upon the rate of advance through the cutting station and the speed of rotation of the support member relative to the cutting station.

2. A process according to claim 1, wherein the support member is advanced through the cutting station at a constant linear speed and the cutting means and the means for laying the optical fibres in the grooves are rotated around the support member at a constant speed.

3. A process according to claim 1, wherein the support member is advanced through the cutting station at a constant linear speed while rotating about its axis at a constant speed of rotation, the cutting means and the means for laying the optical fibres in the grooves being maintained in a fixed position.

4. A process accordng to any one of the preceding claims, including the additional step of sheathing the support member, after formation of the grooves and laying therein of the optical fibres, with an outer sheath.

5. A process according to claim 1 substantially as hereinbefore described with reference to Figs. 1 and 3 to 7 of the accompanying drawings.

6. Apparatus for carrying out the process of claim 1, comprising a supply means for the ungrooved support member, a receiving means for the grooved support member comprising the optical fibres mounted therein, a cutting station located between the supply means and the receiving means, means for advancing the support member along a linear path from the supply means to the receiving means and through the cutting station, cutting means located in said cutting station for forming a plurality of grooves in the surface of the support member as it passes therethrough, means downstream of the cutting station and upstream of the receiving station for laying an optical fibre into each of said grooves said fibre laying means being at a fixed angular and linear distance from the cutting means, and means for rotating the support member relative to the cutting means and the fibre laying means as it passes thereby.

7. Apparatus according to claim 6, wherein the cutting means and the fibre laying means are rotatable as a unit about the support member as it is advanced at a constant linear speed from the supply to the receiving means and said rotating means are operable so as to rotate the cutting and fibre laying means about the axis of the support member.

8. Apparatus according to claim 6, wherein the supply means and the receiving means are fixed relative to each other for rotary movement about the axis of the support member as it is advanced along said path and are driven in rotation about said path during the linear movement of the support member by said rotating means, the cutting means and the fibre laying means being fixed in a stationary position.

9. Apparatus according to claim 8 comprising means for driving the support member along said path and for blocking twisting thereof, said driving and blocking means being located between the supply means and the cutting means and rotatable about the axis of the support member at the same speed as the rotation of the supply and receiving means.

10. Apparatus according to claim 9, wherein said driving and blocking means comprise two endless belts mounted on rollers on opposite sides of the support member, and which serve to grip the support member therebetween as it moves along said path.

11. Apparatus according to claim 9, wherein driving and blocking means comprise two cylinders which are rotatable about axes which are perpendicular to the path movement of the support member and around which the support member may be wound.

12. Apparatus according to claim 9, 10 or 11, comprising similar means for blocking twisting of the support member downstream of the cutting means but upstream of the fibre laying means.

1 3. Apparatus according to claim 9, 10, 11 or 12, including further means for blocking twisting of the support member downstream of the fibre laying means and upstream of the receiving means.

14. Apparatus according to claim 7 including means for blocking twisting of the support member upstream of the cutting means but downstream of the supply means.

1 5. Apparatus according to any one of claims 6 to 14 additionally comprising means for sheathing the support member downstream of the fibre laying means but upstream of the receiving means.

1 6. Apparatus according to claim 15, wherein the sheathing means comprise a means for winding a strip around the support member to form a helically wound sheath thereon.

1 7. Apparaus according to any one of claims 6 to 16, wherein the fibre laying means comprises a guide which penetrates into the groove in the support member and a roller supported in said guide for precisely depositing the fibre in its groove.

1 8. Apparatus according to any one of claims 6 to 1 7 comprising a means for controlling the tension of the support member, said controlling means comprising a drive capstan which imparts to the support member a defined degree of elongation corresponding to the over-length required for laying the fibres in helical forms in said grooves.

19. Apparatus according to claim 6, substantially as hereinbefore described with reference to Figs. 3 to 5 of the accompanying drawings.