CA1083393A - Load bearing optical fiber cables - Google Patents
Load bearing optical fiber cablesInfo
- Publication number
- CA1083393A CA1083393A CA304,970A CA304970A CA1083393A CA 1083393 A CA1083393 A CA 1083393A CA 304970 A CA304970 A CA 304970A CA 1083393 A CA1083393 A CA 1083393A
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- Canada
- Prior art keywords
- filament
- dielectric optical
- optical waveguides
- grooves
- guide means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Abstract of the Disclosure An optical cable is assembled by inserting dielectric optical waveguides into a filament having periodically reversing helical grooves. Dielectric optical waveguide is unwound from fixed reels by movement of the filament past the reels. A rotatable guide unit has flexible tubes through which dielectric optical waveguide is guided, the tube ends being disposed within the grooves so that respective dielectric optical waveguides and grooves are maintained circumferentially coincident.
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Description
1083393 ;:
This invention relates to a method and apparatus for use in the assembly of optical cables.
It has been previously proposed to manufacture optical cables having a central strength member of, for example, steel wire, a plastics outer sleeving extruded around the steel wire and a series of grooves formed in the surface of the plastic sleeving, each groove conta;ning a dielectric optical waveguide.
In order to ensure that dielectric optical waveguides are not subject to destructive tensile and compressive stresses wherever the cable is bent, the grooves are made in helical form.
Thus at a curved part of a cable a dielectric optical waveguide .
experiences alternately compression and tension and over the length of the curve, the stresses at least partially cancel out. -The manufacturing steps for such cable include production of a grooved, plastics-coated metal strength member to ;
provide a central filament for the cable, and the laying of dielectric optical waveguides into the grooves in the central filament. In the former, a known practice is to extrude the plastics through a rotating die, a servo mechanism being utilized to maintain the correct ratio of die angular velocity to the extrusion rate of filament in order to maintain the pitch of the helices within a predetermined range throughout the length of the central filament.
It is necessary to limit the extrusion rate in order to guard against adverse shear affects resulting when the plastics, as it is `
extruded in one direction, is directed rapidly in a different direction.
Care must also be taken in choosing an extrusion rate to avoid collapse of the grooved structure immediately the malleable, high temperature plastics exits from the die.
To lay dielectric optical waveguides into an approp-riately grooved central filament, a planetary stranding technique :
, ~ . .
~0~33393 has been adopted. In such a technique for laying in, say ten dielectr~c opttcal waveguides, ten reels of dielectric optical waveguide arè mounted on a rotatable jig with the central filament being led through the centre of the jig. The reels revolve around the longitudinally moving filament with an angular velocity commensurate with both the pitch of the helical grooves and the velocity of the -central filament. In effect therefore a reel follows a groove around as the central filament is fed through the jig. A suitable locating device presses payed out dielectric optical waveguide into the grooves.
Rotation of the reels and their motion around the central filament does, however, introduce a twist into the laid dielectric optical waveguide which is unacceptable because of the internal stresses which result. To compensate for this the reels ~ ;
are themselves rotated so that the undesirable twist in the dielectric optical waveguide is pre-empted. The nature of the movement of the reels somewhat resembles a planet system and accounts for the name given to this technique.
It will be appreciated that a complex servo mechanism is required to correctly interrelate the speeds at which:-1) the centre filament is fed through the jig;
This invention relates to a method and apparatus for use in the assembly of optical cables.
It has been previously proposed to manufacture optical cables having a central strength member of, for example, steel wire, a plastics outer sleeving extruded around the steel wire and a series of grooves formed in the surface of the plastic sleeving, each groove conta;ning a dielectric optical waveguide.
In order to ensure that dielectric optical waveguides are not subject to destructive tensile and compressive stresses wherever the cable is bent, the grooves are made in helical form.
Thus at a curved part of a cable a dielectric optical waveguide .
experiences alternately compression and tension and over the length of the curve, the stresses at least partially cancel out. -The manufacturing steps for such cable include production of a grooved, plastics-coated metal strength member to ;
provide a central filament for the cable, and the laying of dielectric optical waveguides into the grooves in the central filament. In the former, a known practice is to extrude the plastics through a rotating die, a servo mechanism being utilized to maintain the correct ratio of die angular velocity to the extrusion rate of filament in order to maintain the pitch of the helices within a predetermined range throughout the length of the central filament.
It is necessary to limit the extrusion rate in order to guard against adverse shear affects resulting when the plastics, as it is `
extruded in one direction, is directed rapidly in a different direction.
Care must also be taken in choosing an extrusion rate to avoid collapse of the grooved structure immediately the malleable, high temperature plastics exits from the die.
To lay dielectric optical waveguides into an approp-riately grooved central filament, a planetary stranding technique :
, ~ . .
~0~33393 has been adopted. In such a technique for laying in, say ten dielectr~c opttcal waveguides, ten reels of dielectric optical waveguide arè mounted on a rotatable jig with the central filament being led through the centre of the jig. The reels revolve around the longitudinally moving filament with an angular velocity commensurate with both the pitch of the helical grooves and the velocity of the -central filament. In effect therefore a reel follows a groove around as the central filament is fed through the jig. A suitable locating device presses payed out dielectric optical waveguide into the grooves.
Rotation of the reels and their motion around the central filament does, however, introduce a twist into the laid dielectric optical waveguide which is unacceptable because of the internal stresses which result. To compensate for this the reels ~ ;
are themselves rotated so that the undesirable twist in the dielectric optical waveguide is pre-empted. The nature of the movement of the reels somewhat resembles a planet system and accounts for the name given to this technique.
It will be appreciated that a complex servo mechanism is required to correctly interrelate the speeds at which:-1) the centre filament is fed through the jig;
2) dielectric optical waveguide is payed out;
3) the jig is rotated, and
4) the reels are rotated.
An optical cable structure forming the subject of our co-pending patent application serial no. 304,916, filed 7 June 1978, permits the simplification of operating techniques for manufacture of optical cable. In the co-pending application there is disclosed a filament for an optical cable, the filament having a grooved surface, the grooves being in the form of helices, each helix changing hand along the filament.
The filament structure enables a relatively simple technique, for laying dielectric optical waveguides into the filament grooves. For use in the technique, apparatus comprises a plurality of dielectric optical waveguide stores, wh;ch can be reels, the stores being fixedly located around a feedpath for the filament, a reciprocally rotatable guide means located radially outwardly of said feed path for guiding individual dielectric optical waveguides from the stores to respective grooves and a locating device for positioning -individual optical waveguides into said grooves. Dimensions of the helices can be so chosen that the periodic change of hand produces no net circulation of a groove around a longitudinal axis of the filament. Clearly, this obviates the need for rotation of the `
individual dielectric optical waveguide stores or reels.
The locating device preferably taken the form of a circular array of flexible tubes, each tube being adapted to accommodate a dielectric optical waveguide and having one end mounted at the guide means and its other end urged into and substantially parallel to a respective groove. The guide means can be a plurality of longitudinally spaced, relatively-rotatable guide units and a drive system producing differential rotation of the guide units. In this way total angular movement of dielectric optical waveguides in passing through the guide means can be phased between guide units. In a further aspect of the invention there is provided a method of laying dielectric optical waveguides into the filament defined to produce an optical cable, comprising feeding filament along a path, paying out dielectric optical waveguides from fixed stores distributed around said path, leading payed out dielectric optical waveguides from respective stores into respective grooves through guide means located radially outwardly of the path, and rotating the guide means firstly in one direction and subsequently in the opposite direction .
so that individual dielectric optical waveguides circumferentially , follow respective ones of the filament grooves where the dielectric optical waveguides exit from the guide means.
An embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which:-Figure 1 is a perspective view of a length of filamentaccording to the invention;
Figure 2 is a schematic representation of apparatus ~-for making such a filament and laying dielectric optical waveguides into grooves in the filament; -Figures 3 and 4 are respectively a perspective view 1 `
and an end view of part of the apparatus for twisting extruded material to produce the filament; and ~;
.:, Figure 5 is a perspective view of apparatus for laying dielectri~ optical waveguides into the filament.
Referring to the drawings in detail, a filament for ~ ;
an optical cable has a central steel wire strength member 1 and, extruded over the strength member 1, a sleeve 2 of high density polyethylene. Formed in the surface of the sleeve and extending ~ ;
throughout the length of the filament are a number, in this case four, circumferentially spaced grooves 3a, 3b, 3c and 3d. In use the grooves each accommodate a dielectric optical waveguide in a relatively loose fit, the whole being surrounded by an extruded plast;cs sheath (not shown). In order to guard against breakage of dielectric optical waveguides where the optical cable is bent, the grooves are made to follow a helical path around the longitudinal axis of a filament. However, as shown at positions 4 the various helical paths followed by the grooves change hand (left to right or right to left~ or lay direction. The grooves 3 are advantageously distributed evenly around the filament so the changes of hand of the 1083393 ~
four helical paths take place at the same specific positions along the length of the filament. The grooves thus have a generally parallel disposition relative to one another. As is evident from Figure 1 the changes of hand take place at regular intervals along the filament.
Turning to Figure 2, there is shown a schematic representation of apparatus used in the manufacture of an optical -cable utilizing the filament described. Basically the apparatus comprises three units, an extrusion unit 5, a twist unit 6, and a laying-in unit 7. To manufacture, steel wire core 1 and a charge of high density polyethylene 8 are fed into an extrusion unit which `
includes a die 9 shown in greater detail in Figure 3. The polyethylene 8 is heated until it is malleable and then extruded around the steel wire core 1 through the die 9 which is shaped to form grooves 10 in ;~
the polyethylene as it exits the extrusion unit 5. Some way downstream of the extrusion unit, the filament, having been cooled by a trough of cooling fluid (not shown) becomes relatively rigid and enters the twist unit which is operable to twist the filament, therefore introducing the helical form to the grooves where the polyethylene exits the extrusion unit.
Downstream of the twist unit 6 is the laying-in ;
. .
unit at which dielectric optical waveguide 11 which is payed out from reels 12 is set into the grooves 3.
Referring to the more detailed Figure 3, molten polyethylene is extruded through the die 9 which has four inwardly projecting straight-walled fingers 13 to form the grooves 3. A twist unit 6 comprises a mechanism having a central cylindrical bore through which the extruded filament is pulled, the mechanism having at one end a gear 14 which is reciprocally rotatable and is driven by a drive gear 15 which forms part of a drive train from the '
An optical cable structure forming the subject of our co-pending patent application serial no. 304,916, filed 7 June 1978, permits the simplification of operating techniques for manufacture of optical cable. In the co-pending application there is disclosed a filament for an optical cable, the filament having a grooved surface, the grooves being in the form of helices, each helix changing hand along the filament.
The filament structure enables a relatively simple technique, for laying dielectric optical waveguides into the filament grooves. For use in the technique, apparatus comprises a plurality of dielectric optical waveguide stores, wh;ch can be reels, the stores being fixedly located around a feedpath for the filament, a reciprocally rotatable guide means located radially outwardly of said feed path for guiding individual dielectric optical waveguides from the stores to respective grooves and a locating device for positioning -individual optical waveguides into said grooves. Dimensions of the helices can be so chosen that the periodic change of hand produces no net circulation of a groove around a longitudinal axis of the filament. Clearly, this obviates the need for rotation of the `
individual dielectric optical waveguide stores or reels.
The locating device preferably taken the form of a circular array of flexible tubes, each tube being adapted to accommodate a dielectric optical waveguide and having one end mounted at the guide means and its other end urged into and substantially parallel to a respective groove. The guide means can be a plurality of longitudinally spaced, relatively-rotatable guide units and a drive system producing differential rotation of the guide units. In this way total angular movement of dielectric optical waveguides in passing through the guide means can be phased between guide units. In a further aspect of the invention there is provided a method of laying dielectric optical waveguides into the filament defined to produce an optical cable, comprising feeding filament along a path, paying out dielectric optical waveguides from fixed stores distributed around said path, leading payed out dielectric optical waveguides from respective stores into respective grooves through guide means located radially outwardly of the path, and rotating the guide means firstly in one direction and subsequently in the opposite direction .
so that individual dielectric optical waveguides circumferentially , follow respective ones of the filament grooves where the dielectric optical waveguides exit from the guide means.
An embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which:-Figure 1 is a perspective view of a length of filamentaccording to the invention;
Figure 2 is a schematic representation of apparatus ~-for making such a filament and laying dielectric optical waveguides into grooves in the filament; -Figures 3 and 4 are respectively a perspective view 1 `
and an end view of part of the apparatus for twisting extruded material to produce the filament; and ~;
.:, Figure 5 is a perspective view of apparatus for laying dielectri~ optical waveguides into the filament.
Referring to the drawings in detail, a filament for ~ ;
an optical cable has a central steel wire strength member 1 and, extruded over the strength member 1, a sleeve 2 of high density polyethylene. Formed in the surface of the sleeve and extending ~ ;
throughout the length of the filament are a number, in this case four, circumferentially spaced grooves 3a, 3b, 3c and 3d. In use the grooves each accommodate a dielectric optical waveguide in a relatively loose fit, the whole being surrounded by an extruded plast;cs sheath (not shown). In order to guard against breakage of dielectric optical waveguides where the optical cable is bent, the grooves are made to follow a helical path around the longitudinal axis of a filament. However, as shown at positions 4 the various helical paths followed by the grooves change hand (left to right or right to left~ or lay direction. The grooves 3 are advantageously distributed evenly around the filament so the changes of hand of the 1083393 ~
four helical paths take place at the same specific positions along the length of the filament. The grooves thus have a generally parallel disposition relative to one another. As is evident from Figure 1 the changes of hand take place at regular intervals along the filament.
Turning to Figure 2, there is shown a schematic representation of apparatus used in the manufacture of an optical -cable utilizing the filament described. Basically the apparatus comprises three units, an extrusion unit 5, a twist unit 6, and a laying-in unit 7. To manufacture, steel wire core 1 and a charge of high density polyethylene 8 are fed into an extrusion unit which `
includes a die 9 shown in greater detail in Figure 3. The polyethylene 8 is heated until it is malleable and then extruded around the steel wire core 1 through the die 9 which is shaped to form grooves 10 in ;~
the polyethylene as it exits the extrusion unit 5. Some way downstream of the extrusion unit, the filament, having been cooled by a trough of cooling fluid (not shown) becomes relatively rigid and enters the twist unit which is operable to twist the filament, therefore introducing the helical form to the grooves where the polyethylene exits the extrusion unit.
Downstream of the twist unit 6 is the laying-in ;
. .
unit at which dielectric optical waveguide 11 which is payed out from reels 12 is set into the grooves 3.
Referring to the more detailed Figure 3, molten polyethylene is extruded through the die 9 which has four inwardly projecting straight-walled fingers 13 to form the grooves 3. A twist unit 6 comprises a mechanism having a central cylindrical bore through which the extruded filament is pulled, the mechanism having at one end a gear 14 which is reciprocally rotatable and is driven by a drive gear 15 which forms part of a drive train from the '
- 5 -1083393 :::
.
extrusion unit, this being shown schematically by arrows B and C ~ ;
and drive shaft 16, the function of the drive train being to relate the speed of oscillation of the gear 14 to the extrusion rate of the extrusion unit 5. Alternatively the rates of extrusion and drive to the twist unit can be preset to obtain the required , .: .
groove characteristics without the drive train B and C.
Integral with, and adjacent gear 14, is a barrel member 16 having a series o~ four evenly circumferentially spaced slots 17 extending through its wall. Slidably mounted within the slots for limited radial movement are four fins 18 having blades l9 of thin cross-section at their inner edges which project into the barrel 16. Outer edges 20 of the fins 18 are biased radially -inwardly by a spring 21.
In operation of the twist unit 6, the blades 19 interengage in respective ones of the four grooves 3 where the extruded plastics is relatively cool and rigid and the drive train, via the gear 14, drives the barrel 16 to twist the filament 2. Since the extrusion unit does not rotate, the extruded polyethylene between the two units 5 and 6 undergoes a shear stress resulting in the grooves in the most malleable part of the polyethylene, i.e. as it exits from the extrusion unit 5, being deformed to provide the helical character. The change in hand of the individual helices is achieved merely by reversing the drive direction of the drive train.
The blades 19 are in an alternative embodiment,(not shown), replaced by miniature wheels which run in the grooves 3 in the filament 2 with somewhat less friction than do the blades 19.
In another alternative (not shown) the filament is gripped at its surface by three wheels of res;lient composition. The arrangement is such that the wheels bear sufficiently strongly on the filament that it can be twisted by the twist unit but insufficiently .
~)83393 :~
strongly for the grooved surface structure to be permanently distorted.
Figure 4 shows a practical embodiment of the unit 7 for laying dielectric optical waveguides 11 into the grooves 3 of a filament 2. Dielectric optical waveguide is payed out from four reels 12 which are evenly circumferentially spaced away from a path 21 along which the grooved filament 2 is drawn. The dielectric optical waveguides 11 are pulled from the reels by the movement of the filament itself as will be explained presently. The dielectric optical waveguides 11 pass through guide means comprising a pair of rotatable plates 22 and 23. The filament 2 is drawn through the centre of the two plates while the dielectric optical waveguides pass through the plates at circumferential evenly spaced apertures 24 and 25. The plate 23 is somewhat thicker than plate 22 and the apertures 25 are lined with tubes 26 which project from the downstream side of the plate 23. The tubes 26 are inclined towards the axis of the ~-filament 2 and their ends 27 are flexible and pressed into respective grooves 3 so that as dielectric optical waveguide is drawn frorn the tubes by the filament being drawn past the laying-in unit 7, the dielectric optical waveguides are automatically located in the bases of the grooves 3. To aid the drawing out of dielectric optical waveguide, the outlet ends of the tubes are tapered, the tapered surface facing radially outward. In addition, the inlet ends of each of the tubes can be formed with a mouthpiece (not shown) to reduce friction effects where dielectric optical waveguide enters the tubes.
The circumferential position of the grooves 3, where `-they are engaged by tube ends 27, regulate the angular position of the plate 23. A geared drive shown schematically as arrow D relates the rotation of plate 22 to that of plate 23.
In operation the movement of filament 2 past the tube - - :
ends 27 produces rotation of plate 23 determined by the number of -times a helical groove 3 extends around the longitudinal axis of the filament 2 between adjacent changes of hand or lay direction. The purpose of the second plate 22 is to prevent the four fibres from contacting each other and the central filament. The latter is undesirable slnce friction effects would make the pulling of fibre from the fixed reels 12 much more difficult. The presence of the plate 22 permits a phased winding of the dielectric optical waveguides 11 around each other and the central filament 2, but without there being any contact. If a number of turns are envisaged between each change of hand of the helical grooves 3 then a number of intermediate plates 22 can be sited between the plate 23 and the reels 12 with an appropriate gear drive.
In the embodiment described the drive is such as to produce angular rotation of 2 of plate 22 for every angular rotation of the plate 23.
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~083393 ~;SUPPLEMENTARY DISCLOSURE -~
In a modification of this apparatus, means are prov;ded for reduc;ng tension in dielectric optical waveguides positioned in said grooves~
Tension in the waveguides of the finished cable is undesirable since it both increases light loss from the waveguides and increases the chance of waveguide fracture. -Preferably the tension reducing means is adapted to introduce an element of slackness in the waveguides positioned within said grooves.
Said tension reducing means can include a drawing -mechanism located upstream of the guide means, said drawing mechanism being driveable to draw dielectric optical waveguides -~
from said respective stores and to present such waveguides, in a ;
slack condition, to said guide means.
The drawing mechanism can comprise a pair of horizontal, resilient rollers pressed together to pinch dielectric optical waveguides therebetween. The stores can be reels located l;
close to a vertical plane containing said feedpath, said reels having substantially horizontal rotational axes~
Particularly for use with plastics coated dielectric optical waveguides, said tension reducing means can be an adaptation of said locating means to minimize frictional engagement between said locating means and said dielectric optical waveguides. Thus said guide means can comprise a rotatable support having a central aperture through which the filament is advanced along said feedpath and a first array of bores located rad;ally outwardly of the aperture to loosely receive respective dielectric optical waveguides therein; said locating device can comprise a plurality of rods mounted within respective ones of a second circular array of bores g ~083393 extending through the support, the bores of said second array inclined to the feedpath and radially spaced from sa;d ~;rst array, each rod having an aperture at its end to loosely receive a dielectric optical waveguide. This arrangement is particularly adapted for use with plastics coated dielectric optical waveguides since any waveguide coating which is inadvertently stripped as the waveguide passes through the aperture is unlikely to lodge within the aperture, so frictional engagement is minimized.
The tension reducing means can further include a thrust bearing for mounting the rotatable guide means relative to a support structure. Low friction within the bearing is important since only a small moment is available to turn the guide means, this being provided by interengagement of the locating means within the filament grooves downstream of the bearing.
The apparatus can further include tape winding means for winding tape helically around the filament as the filament exits from said guide means. Although the tape winding means primarily functions to maintain dielectric optical waveguides within ' their associated grooves, frictional engagement between the dielectric optical waveguides and surrounding tape can provide a multiplicity of anchor points for the dielectric optical waveguides downstream of said guide means.
Embodiments of the invention incorporating the tension reducing means will now be described by way of example with references to the accompanying drawings, in which:-Figure 7 is a schematic respresentation of part ofa cabling process for the fabrication of the optical cable, Figure 8 is a perspective view of a device for drawing dielectric optical waveguide from reels and delivering it to a laying-in unit;
Figure 9 is a part sectional view of a mechanism ~-for laying dielectric optical waveguide into grooves in the filament; and Figure 10 is a part sectional view of a mechanism -for taping dielectric optical waveguides to the grooved filament. -~
Referring to the Figures 7 to 10, Figure 7 shows -a schematic representation of cabling apparatus for use with the ~ , filament. The filament is pulled in the direction of arrow A past a dielectric optical waveguide store, a drawing unit, and through the centres of a laying-in unit and a taping unit.
As shown in Figure 8, dielectric optical waveguides are payed out from four reels 112 which are distributed close to the vertical plane containing the feed direction of the filament 102.
The dielectric optical waveguides 111 are pulled from the reels by ;
, . -a pair of rollers 130 having slightly resilient surfaces, the rollers ~;
being pressed together to pinch the dielectric optical waveguides 111, so that when one of the rollers 130 is driven, the waveguides 111 : .
are drawn from the reels 112. The waveguides on the downstream sideof the rollers 130 extend through a fixed plate 131 having distribution holes 132, the waveguides subsequently being led to the laying-in unit shown in greater detail in Figure 9. The rollers 130 are ; -driven at a speed such that a length of each waveguide hangs between -the rollers 130 and the plate 131, the hanging portions of the waveguide preventing undesirable tension from being applied to the -waveguides as they are drawn from the plate 131. Without th~
rollers 130, the tension in the waveguides depends both on the !~
extent to which the reels 112 are balanced and on the friction in the bearings of the reels. Since it is extremely difficult both to maintain a reel permanently in balance, and to equalize the bearing friction of the reels, then, without rollers 130, differential -- 1 1 _ ~
., , ,.. ,. ; ..,,,," .. -.-.-.... .. , :
~ 083393 tensile stresses may result in the dielectric optical waveguides of the finished cable.
Downstream of the drawing unit is the laying-in unit, shown in greater detail in Figure 9. As the cable is pulled (not shown) downstream of the taping unit, filament 102 is consequently pulled through the centre of the laying-in unit and dielectric optical waveguides 111 are pulled through the distribution holes 132 in the fixed plate 131. The dielectric optical waveguides 111 pass through guide means comprising a rotatable plate 123 which is mounted relative a support structure 134 by means of a thrust bearing shown schematically at 133. Rods or needles 137 are mounted in a circular array of holes 131, each of the rods having an aperture 140 at its outer end through which a waveguide 111 is threaded. The rods are inclined towards the axis of the filament 102 with the apertured parts of the rods 137 placed into respective grooves 103. The dielectric optical wave-guides run freely through an inner circular array of holes 130 in the plate 123 and are located in the grooves as they pass through the aperture 140. This embodiment is particularly adapted for use with plastics coated dielectric optical waveguides to reduce dynamic friction between the rods and the waveguides and to inhibit build-up of coating which might inadvertently be stripped as a waveguide passes through an aperture. -The rods 137 each have a groove 135 to receive the end of a set screw 136 located in a threaded bore within the plate 123. The position of the rods 137 within the plate can thus be ;~
altered to accomodate differently sized filaments.
As shown in Figure 10, a bind~ng unit 138 which, in use, is located interjacent the laying-in unit 107 and a take-up reel (not shown) has a rotary drum 139 on which thin plastics tape 143, for example *Mylar, is double wound. The drum 139 has a friction bearing, represented schematically at 144, relative to a support 145, Independently rotatably mounted, and driven by a drive represented schematically by Dl taken from the laying-in unit, is a strtpping device which has a central hub 146, two booms 141 and a pair of rings 142, one ring located generally centrally of the drum and the other ring located upstream of the ~;~
drum.
As the stripping device is rotated about the axis of filament 102, tape 143 is drawn from the drum 139, which is -~
correspondingly rotated against the friction bearing, the tape being automatlcally helically wound around the advancing filament 102. To accurately locate the tape, a horn 146 tapers towards a binding position which ls just downstream of the laying-in unit.
The tape 143 serves to keep the dielectric optical waveguides in place until plastic sheath is applied. This is especially useful if the filament is wound before being sheathed, since, in the wound condition, lengths of the dielectric optical waveguide 111 facing :
the tape-up reel hub experience a net force tending to eject them from the grooves 103 and this tendency is arrested by the binding tape 139. As mentioned previously the tape where it frictionally engages dielectric optical waveguide provides a multiplicity of ;
anchor points to inhlbit tension from being applied to dielectric optical waveguides once they have been layed in their respective grooves. ;~
The reduction in rotating friction of the plate 123 provided by the thrust bearing 133 is important since only a small moment is aYailable to turn the plate 123, this being provided by the interengagement of the rods 137 whose ends follow the movement of grooves 103 in the filament 102.
* Trademark C
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extrusion unit, this being shown schematically by arrows B and C ~ ;
and drive shaft 16, the function of the drive train being to relate the speed of oscillation of the gear 14 to the extrusion rate of the extrusion unit 5. Alternatively the rates of extrusion and drive to the twist unit can be preset to obtain the required , .: .
groove characteristics without the drive train B and C.
Integral with, and adjacent gear 14, is a barrel member 16 having a series o~ four evenly circumferentially spaced slots 17 extending through its wall. Slidably mounted within the slots for limited radial movement are four fins 18 having blades l9 of thin cross-section at their inner edges which project into the barrel 16. Outer edges 20 of the fins 18 are biased radially -inwardly by a spring 21.
In operation of the twist unit 6, the blades 19 interengage in respective ones of the four grooves 3 where the extruded plastics is relatively cool and rigid and the drive train, via the gear 14, drives the barrel 16 to twist the filament 2. Since the extrusion unit does not rotate, the extruded polyethylene between the two units 5 and 6 undergoes a shear stress resulting in the grooves in the most malleable part of the polyethylene, i.e. as it exits from the extrusion unit 5, being deformed to provide the helical character. The change in hand of the individual helices is achieved merely by reversing the drive direction of the drive train.
The blades 19 are in an alternative embodiment,(not shown), replaced by miniature wheels which run in the grooves 3 in the filament 2 with somewhat less friction than do the blades 19.
In another alternative (not shown) the filament is gripped at its surface by three wheels of res;lient composition. The arrangement is such that the wheels bear sufficiently strongly on the filament that it can be twisted by the twist unit but insufficiently .
~)83393 :~
strongly for the grooved surface structure to be permanently distorted.
Figure 4 shows a practical embodiment of the unit 7 for laying dielectric optical waveguides 11 into the grooves 3 of a filament 2. Dielectric optical waveguide is payed out from four reels 12 which are evenly circumferentially spaced away from a path 21 along which the grooved filament 2 is drawn. The dielectric optical waveguides 11 are pulled from the reels by the movement of the filament itself as will be explained presently. The dielectric optical waveguides 11 pass through guide means comprising a pair of rotatable plates 22 and 23. The filament 2 is drawn through the centre of the two plates while the dielectric optical waveguides pass through the plates at circumferential evenly spaced apertures 24 and 25. The plate 23 is somewhat thicker than plate 22 and the apertures 25 are lined with tubes 26 which project from the downstream side of the plate 23. The tubes 26 are inclined towards the axis of the ~-filament 2 and their ends 27 are flexible and pressed into respective grooves 3 so that as dielectric optical waveguide is drawn frorn the tubes by the filament being drawn past the laying-in unit 7, the dielectric optical waveguides are automatically located in the bases of the grooves 3. To aid the drawing out of dielectric optical waveguide, the outlet ends of the tubes are tapered, the tapered surface facing radially outward. In addition, the inlet ends of each of the tubes can be formed with a mouthpiece (not shown) to reduce friction effects where dielectric optical waveguide enters the tubes.
The circumferential position of the grooves 3, where `-they are engaged by tube ends 27, regulate the angular position of the plate 23. A geared drive shown schematically as arrow D relates the rotation of plate 22 to that of plate 23.
In operation the movement of filament 2 past the tube - - :
ends 27 produces rotation of plate 23 determined by the number of -times a helical groove 3 extends around the longitudinal axis of the filament 2 between adjacent changes of hand or lay direction. The purpose of the second plate 22 is to prevent the four fibres from contacting each other and the central filament. The latter is undesirable slnce friction effects would make the pulling of fibre from the fixed reels 12 much more difficult. The presence of the plate 22 permits a phased winding of the dielectric optical waveguides 11 around each other and the central filament 2, but without there being any contact. If a number of turns are envisaged between each change of hand of the helical grooves 3 then a number of intermediate plates 22 can be sited between the plate 23 and the reels 12 with an appropriate gear drive.
In the embodiment described the drive is such as to produce angular rotation of 2 of plate 22 for every angular rotation of the plate 23.
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~083393 ~;SUPPLEMENTARY DISCLOSURE -~
In a modification of this apparatus, means are prov;ded for reduc;ng tension in dielectric optical waveguides positioned in said grooves~
Tension in the waveguides of the finished cable is undesirable since it both increases light loss from the waveguides and increases the chance of waveguide fracture. -Preferably the tension reducing means is adapted to introduce an element of slackness in the waveguides positioned within said grooves.
Said tension reducing means can include a drawing -mechanism located upstream of the guide means, said drawing mechanism being driveable to draw dielectric optical waveguides -~
from said respective stores and to present such waveguides, in a ;
slack condition, to said guide means.
The drawing mechanism can comprise a pair of horizontal, resilient rollers pressed together to pinch dielectric optical waveguides therebetween. The stores can be reels located l;
close to a vertical plane containing said feedpath, said reels having substantially horizontal rotational axes~
Particularly for use with plastics coated dielectric optical waveguides, said tension reducing means can be an adaptation of said locating means to minimize frictional engagement between said locating means and said dielectric optical waveguides. Thus said guide means can comprise a rotatable support having a central aperture through which the filament is advanced along said feedpath and a first array of bores located rad;ally outwardly of the aperture to loosely receive respective dielectric optical waveguides therein; said locating device can comprise a plurality of rods mounted within respective ones of a second circular array of bores g ~083393 extending through the support, the bores of said second array inclined to the feedpath and radially spaced from sa;d ~;rst array, each rod having an aperture at its end to loosely receive a dielectric optical waveguide. This arrangement is particularly adapted for use with plastics coated dielectric optical waveguides since any waveguide coating which is inadvertently stripped as the waveguide passes through the aperture is unlikely to lodge within the aperture, so frictional engagement is minimized.
The tension reducing means can further include a thrust bearing for mounting the rotatable guide means relative to a support structure. Low friction within the bearing is important since only a small moment is available to turn the guide means, this being provided by interengagement of the locating means within the filament grooves downstream of the bearing.
The apparatus can further include tape winding means for winding tape helically around the filament as the filament exits from said guide means. Although the tape winding means primarily functions to maintain dielectric optical waveguides within ' their associated grooves, frictional engagement between the dielectric optical waveguides and surrounding tape can provide a multiplicity of anchor points for the dielectric optical waveguides downstream of said guide means.
Embodiments of the invention incorporating the tension reducing means will now be described by way of example with references to the accompanying drawings, in which:-Figure 7 is a schematic respresentation of part ofa cabling process for the fabrication of the optical cable, Figure 8 is a perspective view of a device for drawing dielectric optical waveguide from reels and delivering it to a laying-in unit;
Figure 9 is a part sectional view of a mechanism ~-for laying dielectric optical waveguide into grooves in the filament; and Figure 10 is a part sectional view of a mechanism -for taping dielectric optical waveguides to the grooved filament. -~
Referring to the Figures 7 to 10, Figure 7 shows -a schematic representation of cabling apparatus for use with the ~ , filament. The filament is pulled in the direction of arrow A past a dielectric optical waveguide store, a drawing unit, and through the centres of a laying-in unit and a taping unit.
As shown in Figure 8, dielectric optical waveguides are payed out from four reels 112 which are distributed close to the vertical plane containing the feed direction of the filament 102.
The dielectric optical waveguides 111 are pulled from the reels by ;
, . -a pair of rollers 130 having slightly resilient surfaces, the rollers ~;
being pressed together to pinch the dielectric optical waveguides 111, so that when one of the rollers 130 is driven, the waveguides 111 : .
are drawn from the reels 112. The waveguides on the downstream sideof the rollers 130 extend through a fixed plate 131 having distribution holes 132, the waveguides subsequently being led to the laying-in unit shown in greater detail in Figure 9. The rollers 130 are ; -driven at a speed such that a length of each waveguide hangs between -the rollers 130 and the plate 131, the hanging portions of the waveguide preventing undesirable tension from being applied to the -waveguides as they are drawn from the plate 131. Without th~
rollers 130, the tension in the waveguides depends both on the !~
extent to which the reels 112 are balanced and on the friction in the bearings of the reels. Since it is extremely difficult both to maintain a reel permanently in balance, and to equalize the bearing friction of the reels, then, without rollers 130, differential -- 1 1 _ ~
., , ,.. ,. ; ..,,,," .. -.-.-.... .. , :
~ 083393 tensile stresses may result in the dielectric optical waveguides of the finished cable.
Downstream of the drawing unit is the laying-in unit, shown in greater detail in Figure 9. As the cable is pulled (not shown) downstream of the taping unit, filament 102 is consequently pulled through the centre of the laying-in unit and dielectric optical waveguides 111 are pulled through the distribution holes 132 in the fixed plate 131. The dielectric optical waveguides 111 pass through guide means comprising a rotatable plate 123 which is mounted relative a support structure 134 by means of a thrust bearing shown schematically at 133. Rods or needles 137 are mounted in a circular array of holes 131, each of the rods having an aperture 140 at its outer end through which a waveguide 111 is threaded. The rods are inclined towards the axis of the filament 102 with the apertured parts of the rods 137 placed into respective grooves 103. The dielectric optical wave-guides run freely through an inner circular array of holes 130 in the plate 123 and are located in the grooves as they pass through the aperture 140. This embodiment is particularly adapted for use with plastics coated dielectric optical waveguides to reduce dynamic friction between the rods and the waveguides and to inhibit build-up of coating which might inadvertently be stripped as a waveguide passes through an aperture. -The rods 137 each have a groove 135 to receive the end of a set screw 136 located in a threaded bore within the plate 123. The position of the rods 137 within the plate can thus be ;~
altered to accomodate differently sized filaments.
As shown in Figure 10, a bind~ng unit 138 which, in use, is located interjacent the laying-in unit 107 and a take-up reel (not shown) has a rotary drum 139 on which thin plastics tape 143, for example *Mylar, is double wound. The drum 139 has a friction bearing, represented schematically at 144, relative to a support 145, Independently rotatably mounted, and driven by a drive represented schematically by Dl taken from the laying-in unit, is a strtpping device which has a central hub 146, two booms 141 and a pair of rings 142, one ring located generally centrally of the drum and the other ring located upstream of the ~;~
drum.
As the stripping device is rotated about the axis of filament 102, tape 143 is drawn from the drum 139, which is -~
correspondingly rotated against the friction bearing, the tape being automatlcally helically wound around the advancing filament 102. To accurately locate the tape, a horn 146 tapers towards a binding position which ls just downstream of the laying-in unit.
The tape 143 serves to keep the dielectric optical waveguides in place until plastic sheath is applied. This is especially useful if the filament is wound before being sheathed, since, in the wound condition, lengths of the dielectric optical waveguide 111 facing :
the tape-up reel hub experience a net force tending to eject them from the grooves 103 and this tendency is arrested by the binding tape 139. As mentioned previously the tape where it frictionally engages dielectric optical waveguide provides a multiplicity of ;
anchor points to inhlbit tension from being applied to dielectric optical waveguides once they have been layed in their respective grooves. ;~
The reduction in rotating friction of the plate 123 provided by the thrust bearing 133 is important since only a small moment is aYailable to turn the plate 123, this being provided by the interengagement of the rods 137 whose ends follow the movement of grooves 103 in the filament 102.
* Trademark C
. ... .; : - - , - : - .. , ,.. , .. .. : " : ~ . , . . ,, ;
Claims (24)
EXLCUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:-
1. Apparatus for laying dielectric optical waveguide into a filament to produce an optical cable, said filament having a surface defining a plurality of grooves, the grooves each having the form of a helix, each said helix changing hand along the filament, the apparatus comprising a plurality of dielectric optical waveguide stores fixedly located around a feedpath for the filament, a reciprocally rotatable guide means located radially outwardly of said feedpath for guiding individual dielectric optical waveguides from respective stores to respective grooves and a locating device for positioning individual dielectric optical waveguides into said grooves.
2. Apparatus as claimed in claim 1 wherein the stores are reels.
3. Apparatus as claimed in claim 1 wherein the locating device comprises a circular array of flexible tubes each tube having one end mounted at said guide means and its other end urged into and substantially parallel to a respective groove.
4. Apparatus as claimed in claim 3, wherein each tube at said one end is formed with a mouthpiece.
5. Apparatus as claimed in claim 3, where the other end of each tube has a tapered end surface, each tapered surface facing radially outwardly of the feedpath.
6. Apparatus as claimed in claim 1 wherein the guide means has a plurality of longitudinally spaced, relatively-rotatable guide units and a drive system producing differential rotation of the guide units.
7. Apparatus as claimed in claim 5, wherein the drive system comprises a geared system having gear ratios such as to distribute total angular movement of dielectric optical waveguides in passing through the guide means, evenly between the guide units.
8. A method of laying dielectric optical waveguides into a filament to produce an optical cable, said filament having a surface defining a plurality of grooves, the grooves each having the form of a helix, each said helix changing hand along the filament, the method comprising feeding filament along a path, paying out dielectric optical waveguides from fixed stores distributed around said path, leading paid out dielectric optical waveguides from respective stores into respective grooves through guide means located radially outwardly of the path, and rotating the guide means firstly in one direction and subsequently in the opposite direction so that individual dielectric optical waveguides circumferentially follow respective ones of the filament grooves where the dielectric optical waveguides exit from the guide means.
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE
9. Apparatus as claimed in claim 1 further comprising means for inhibiting introduction of tension in the dielectric optical waveguides as they are positioned in said grooves.
10. Apparatus as claimed in claim 9 wherein said tension inhibiting means comprises a drawing mechanism located intermediate said stores and said guide means, said drawing mechanism being driveable to draw dielectric optical waveguides from said stores and to present such waveguides, in a slack condition, to said guide means.
11. Apparatus as claimed in claim 10, in which said drawing mechanism comprises a pair of generally horizontal, resilient rollers pressed together to pinch dielectric optical waveguides therebetween.
12. Apparatus as claimed in claim 11, in which said stores are reels located close to a vertical plane containing said feedpath, said reels having substantially horiztonal rotational axes.
13. Apparatus as claimed in claim 9, in which said tension inhibiting means comprises an adaptation of said locating means to reduce frictional engagement between said locating means and said dielectric optical waveguides, said guide means comprising a rotatable support having a central aperture through which the filament is advanced, said support having a first array of bores located radially outwardly of the aperture to loosely receive respective dielectric optical waveguides therein, said locating means comprising a plurality of rods mounted within respective ones of a second circular array of bores extending through the support, the bores of said second array inclined to the feedpath and radially spaced from said first array, said adaptation comprising outer ends of the rods located in respective grooves being apertured to loosely receive respective dielectric optical waveguides.
14. Apparatus as claimed in claim 13, further comprising fixture means associated with each of said second bores to maintain the rods at predetermined positions within the bores.
15. Apparatus as claimed in claim 14, in which each said fixture means comprises a set screw mounted within the support, and a groove extending along an associated rod, said screw adapted to locate within the groove to clamp the rod within a respective bore.
16. Apparatus as claimed in claim 9, in which said tension inhibiting means comprises a thrust bearing mounting said guide means within a fixed support structure.
17. Apparatus as claimed in claim 9, in which said tension inhibitingmeans comprises a tape winding mechanism for winding tape helically around the filament, and dielectric optical waveguides positioned therein, as the filament exits from said guide means.
18. Apparatus as claimed in claim 17, in which said tape winding mechanism comprises a hollow rotatable reel on which such tape is wound, and a stripping device rotatable about said reel to strip tape from the reel and to apply stripped tape as a helical binding to the filament as it is advanced through the hollow reel.
19. Apparatus as claimed in claim 18, in which said reel is mounted for rotation against a friction bearing.
20. Apparatus as claimed in claim 19, in which drive to said stripping device is taken from said guide means.
21. Apparatus as claimed in claim 20, in which said stripping device includes a hub and a boom located radially outwardly of said hub, said boom having eyes integral therewith through which eyes tape is pulled from said reel by rotation of the stripping device.
22. Apparatus as claimed in claim 21, in which said tape is double wound on the reel and said stripping device has a pair of radially opposed booms.
23. Apparatus as claimed in claim 22, further including a member mounted concentrically about said feedpath and located interadjacent said guide and said tape binding means, said member having a conical outer surface for guiding stripped tape from said eyes to a location immediately downstream of said guide means.
24. A method as claimed in claim 8, the improvement comprising maintaining the dielectric optical waveguides substantially free of longitudinal tension downstream of entry thereof into the guide means.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,970A CA1083393A (en) | 1978-06-07 | 1978-06-07 | Load bearing optical fiber cables |
| GB7919564A GB2022644B (en) | 1978-06-07 | 1979-06-05 | Optical cable manufacute |
| DE19792922986 DE2922986A1 (en) | 1978-06-07 | 1979-06-06 | METHOD AND DEVICE FOR MANUFACTURING OPTICAL CABLES |
| FR7914478A FR2428266B1 (en) | 1978-06-07 | 1979-06-06 | IMPROVEMENT IN THE MANUFACTURE OF OPTICAL CABLES |
| JP7070679A JPS5512992A (en) | 1978-06-07 | 1979-06-07 | Improvement in optical cable production |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA304,970A CA1083393A (en) | 1978-06-07 | 1978-06-07 | Load bearing optical fiber cables |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083393A true CA1083393A (en) | 1980-08-12 |
Family
ID=4111644
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,970A Expired CA1083393A (en) | 1978-06-07 | 1978-06-07 | Load bearing optical fiber cables |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5512992A (en) |
| CA (1) | CA1083393A (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS56161508A (en) * | 1980-05-17 | 1981-12-11 | Nippon Telegr & Teleph Corp <Ntt> | Wire rod guide device to supporter fitted with groove |
| JPS57167469A (en) * | 1981-04-03 | 1982-10-15 | Teijin Ltd | Deep dyeing of fiber structure |
| JPS57167470A (en) * | 1981-04-03 | 1982-10-15 | Teijin Ltd | Deep dyeing of fiber product |
| JPS60222809A (en) * | 1984-04-19 | 1985-11-07 | Daiden Kk | Apparatus for producing optical fiber cable |
| FR2565361B1 (en) * | 1984-05-30 | 1986-09-05 | Telecommunications Sa | DEVICE FOR DISTRIBUTING OPTICAL FIBERS IN HELICOIDAL GROOVES OF A JUNC |
| JPH0713688B2 (en) * | 1987-01-16 | 1995-02-15 | 住友電気工業株式会社 | Fiber optic cable |
| JPH0713687B2 (en) * | 1987-01-16 | 1995-02-15 | 住友電気工業株式会社 | Fiber optic cable |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS52126238A (en) * | 1976-04-14 | 1977-10-22 | Hitachi Cable Ltd | Optical communication cable and its manufacture |
-
1978
- 1978-06-07 CA CA304,970A patent/CA1083393A/en not_active Expired
-
1979
- 1979-06-07 JP JP7070679A patent/JPS5512992A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0231362B2 (en) | 1990-07-12 |
| JPS5512992A (en) | 1980-01-29 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |