GB2080967A - An improved method of manufacturing cable - Google Patents

Abstract

In the manufacture of an optical cable comprising helically wound flexible optical cable elements, a faulty optical cable element is replaced by a sound optical cable element in a single operation using a single machine. In the method the cable C is caused to travel in a rectilinear direction, in the direction of its length, and, at a position 14 fixed in space along the advancing cable, the faulty optical cable element is unwound and wound on a take-up reel 5, and at the same time, the sound flexible optical cable element is helically wound from a pay-off reel 10 on to the advancing cable at the fixed position in space, in such a way that the sound optical cable elements fills the helical space vacated by the faulty optical cable element. The method is also applicable to electric cables comprising a layer of bare or insulated electric conductors helically wound around the cable axis. <IMAGE>

Description

SPECIFICATION An improved method of manufacturing cable This invention relates to flexible elongate bodies of the kind comprising at least one layer of flexible elongate elements helically wound around the axis of the elongate body, all such flexible elongate bodies of this kind hereinafter, for convenience, being included in the generic term "cable". The invention is especially, but not exclusively, concerned with an optical cable having at least one layer of flexible elongate optical elements helically wound around the cable axis but it is to be understood that the invention is also applicable to electric cables of the kind comprising at least one layer of bare or insulated elongate electric conductors helically wound around the cable axis.

One known form of optical cable that is especially suitable for use in the transmission of light for communication purposes comprises a central flexible elongate reinforcing member and, surrounding the reinforcing member, at least one layer of flexible elongate elements helically wound around the reinforcing member, each of some or all of the flexible elements comprising a flexible optical element in the form of a rubber or plastics tube in which is loosely housed at least one separate optical fibre and/or at least one optical bundle.Optical fibres and optical bundles are of very small cross-sectional area and are extremely fragile and, during manufacture of an optical cable of the aforesaid kind, there is a risk that an optical fibre or optical bundle loosely housed in a rubber or plastics tube will break or fracture or will be otherwise so damaged that it is no longer suitable for the transmission of light along the length of the cable. The cost per unit length of optical fibre and the cost of manufacture of optical cable elements and of the optical cable itself are such that it is highly undesirable to scrap an optical cable because an optical fibre or optical bundle of one of the optical cable elements has been so damaged that it is no longer serviceable. On the other hand it is also undesirable for an optical cable to be installed with an unserviceable optical element.

It is an object of the present invention to provide a method of manufacturing a cable as hereinbefore defined in which a faulty flexible elongate element of the cable is replaced by a sound flexible elongate element.

According to the invention the method comprises causing the cable to travel in a rectilinear direction in the direction of its length; unwinding from the advancing cable at a position fixed in space along the advancing cable at least one helically wound faulty flexible elongate element; and helically winding a sound flexible elongate element on to the advancing cable at said fixed position in such a way that the sound flexible elongate element fills the helical space vacated by the faulty flexible elongate element.

Where the helically wound flexible elongate elements of the layer are held on the cable by at least one overlying layer of helically wound ribbon, tape, string or other flexible elongate binder (all such flexible elongate binders hereinafter, for convenience, being included in the generic term "tape"), preferably, at a position upstream of the fixed position along the advancing cable at which the faulty flexible elongate element is replaced, the or each overlying helically wound tape is unwound from the cable and, preferably also, at a position downstream of said fixed position along the advancing cable, at least one tape is helically wound around the layer of helically wound flexible elongate elements.

The faulty flexible elongate element which is unwound from the advancing cable is preferably wound on to a drum or reel so that any part or parts of the faulty flexible elongate element that may be sound and re-usable can be readily recovered in a separate operation.

The invention also includes apparatus for use in the manufacture of a cable as hereinbefore defined, which apparatus comprises means for causing the cable to travel in a rectilinear direction in the direction of its length under a substantially constant tension; an unwinding head which is rotatable about the cable axis and which supports at least one take-up reel; a winding head which is longitudinally spaced from the unwinding head along, and is rotatable about, the cable axis and which supports at least one pay-off reel; means for rotatably driving the unwinding and winding heads about the cable axis in the same rotational direction and at the same rotational speed; means for rotatably driving the or each take-up reel about its axis; means for rotatably driving the or each pay-off reel about its axis; and, at a position fixed in space intermediate of the unwinding and winding heads, guide means for guiding a faulty flexible elongate element being unwound from the cable to the take-up reel or one of said take-up reels and for guiding a sound flexible elongate element from the pay-off reel or one of said payoff reels and into the helical space on the cable vacated by the faulty flexible elongate element.

Preferably, the unwinding and winding heads aye secured to opposite ends of a common frame which is rotatably driven about the cable axis with the cable travelling through the centres of the unwinding and winding heads. Preferably, also, each take-up reel and pay-offreel is so supported by its head that its axis lies in a plane radial to the cable axis. In a preferred embodiment, the unwinding head lies downstream of the intermediate guide means and the winding head lies upstream of the intermediate guide means.

The or each take-up reel may have, associated with the reel, a traverse mechanism for winding the faulty flexible elongate element in regular layers on the reel so that a sound part or sound parts of the flexible element can subsequently be readily recovered from the reel in a separate operation.

The intermediate guide means preferably comprises a tubular die which is supported on the common frame approximately mid-way between the winding and unwinding heads and through which the cable will travel and, upstream of and downstream of the die, freely rotatable guide pulleys which are also mounted on the common frame. Preferably, the tubular die is freely rotatable about its axis and, over an intermediate part of the length of its bore, is so shaped or carries means that will engage in the helical space vacated by the faulty optical cable element. For example, the intermediate part of the bore of the tubular die may have an integral inwardly projecting helical flute or may carry a freely rotatable wheel or roller that will engage in and maintain the helical space vacated by the faulty optical cable element.

Alternatively, the tubular die may be fixed and in this case, the bore of the die will be smooth.

The head that is upstream of the intermediate guide means may also support coaxial with the head, a rotatably driven take-up spool for unwinding from the advancing cable and collecting a binder tape which is helically wound around the cable. The head that is downstream of the intermediate guide means may also support, coaxial with the head, at least one rotatably driven carrier for a pad or pads of binder tape to be helically wound around the cable. Appropriate tape guide means is preferably associated both with the tape take-up spool and with the tape carrier.

The means for causing the cable to travel in a rectilinear direction in the direction of its length preferably comprises at least one pair of endless belts by which the cable can be drawn.

The endless belt take-up device or devices, the common frame and the take-up and pay-off reels are preferably driven from a common motor through an infinitely variable speed gear box so that the speed of advance of the cable, the rotational speed of the common frame and the rotational speed of the take-up and pay-off reels can be inter-related with the length of lay of the helically wound flexible elongate elements of the cable. Braking of the take-up and pay-off reels relative to the diameter of the flexible element on the reel is preferably so controlled that the flexible element being unwound from the cable and the flexible element being wound on the cable can be maintained under substantially constant tension.

The invention is further illustrated by a description, by way of example, of improved apparatus for use in the manufacture of an optical cable by means of which a faulty optical cable element of the cable can be replaced by a sound optical cable element, with reference to the accompanying drawing which shows a side elevation of the apparatus.

The optical cable for use with which the apparatus illustrated in the drawing has been particvlarly designed, comprises a central flexible reinforcing wire around which are helically laid eight plastics tubes in each of some of which is loosely housed a separate optical fibre. The plastics tubes are held around the central reinforcing wire by a helically lapped binder tape.

Referring to the drawing, the apparatus comprises an elongate frame 1 at one end of which, the downstream end, is an unwinding head 2 and at the other end of which the upstream end, is a winding head 3. An optical cable C in which a faulty optical cable element is toabe replaced can be caused to travel in a rectilinear direction in the direction of its length through the centres of the winding and unwinding heads 3, 2 by means of an endless belt take-up device 4.

The unwinding head 2 supports a rotatably driven take-up reel 5 associated with which is a traverse mechanism 6. Also supported on and coaxial with the unwinding head 2 is a rotatably > driven carrier 7 for pads 8 of binder tape to be helically wound around the cable C via a guide 9.

The winding head 3 supports a rotatably driven pay-off reel 10 and, co-axial with the head, a rotatably driven take-up spool 1 t for unwinding from the cable C and collecting the binding tape which is helically wound around the cable.

Supported by the frame 1 intermediate the heads 2, 3 is guide means comprising a freely rotatable central tubular die 14 through which the cable C will travel, which, over an intermediate portion of the length of its bore, has a helical flute that will engage in the helical space on the cable vacated by the faulty optical cable element and which has a throated opening at each of its ends and, at each end of the die, free tiotatable pulleys 15, 16.

The endless belt take-up device 4, the frame 1 and the take-up and pay-off reels 5 and 10 are driven through appropriate gearing from a common motor (not shown). The take-tip spool 11 is driven by motor 17 and the carrier 7 Is driven by motor 18.

In use, cable C is caused to travel through the appratus and frame 1 is rotatably' driven about the cable. As the frame 1 rotates, the binder tape is unwound from the cable C by and is collected on the spool 11 and the faulty optical cable element is unwound from the cable at the die 14 and wound on the take-up reel 5 via the guide pulley 1 5 and traverse mechanism 6. At the same time a sound optical cable element from the pay-off reel 10 passes around the guide pulley 1 6 and, at the die 14, is wound in the helical space on the cable vacated by the faulty optical cable element. A binder tape from a pad 8 on the carrier 7 is helically wound around the repaired cable.

The method and apparatus of the invention * have the important advantage that they provide for simple and inexpensive repalrof optical cable with substantial saving in scrt-p material.

Claims (19)

1. A method of manufacturinga cable as hereinbefore defined having a faulty flexible elongate element which method comprises causing the cable to travel in a rectilinear direction in the direction of its length; unwinding from the advancing cable at a position fixed in space along the advancing cable at least óhe helically wound faulty flexible elongate element,çnd helically winding a sound flexible elongate element onto the advancing cable at said fixed position in such a way that the sound flexible elongate element fills the helical space vacated by the faulty flexible elongate element.

2. A method as claimed in Claim 1 in which the helically wound flexible elongate elements of the cable are held on the cable by at least one overlying layer of helically wound tape or other flexible elongate binder, wherein, at a position upstream of the fixed position along the advancing cable at which the faulty flexible elongate element is replaced, the or each overlying helically wound tape is unwound from the cable and, at a position downstream of said fixed position along the advancing cable, at least one tape is helically wound around the layer of helically wound flexible elongate elements.

3. A method as claimed in Claim 1 or 2, wherein the faulty flexible elongate element which is unwound from the advancing-cable is wound onto a drum or reel.

4. Apparatus for use in the manufacture of a cable as hereinbefore defined, which apparatus comprises means for causing the cable to travel in a rectilinear direction in the direction of its length under a substantially constant tension; an unwinding head which is rotatable about the cable axis and which supports at least one take-up reel; a winding head which is longitudinally spaced from the unwinding head along, and is rotatable about, the cable axis and which supports at least one payoff reel; means for rotatably driving the unwinding and winding heads about the cable axis in the same rotational direction and at the same rotational speed; means for rotatably driving the or each take-up reel about its axis; means for rotatably driving the or each payoff reel about its axis; and, at a position fixed in space intermediate of the unwinding and winding heads, guide means for guiding a faulty flexible elongate element being unwound from the cable to the take-up reel or one of said take-up reels and for guiding a sound flexible elongate element from the payoff reel or one of said payoff reels and into the helical space on the cable vacated by the faulty flexible elongate element.

5. Apparatus as claimed in Claim 4, wherein the unwinding and winding heads are secured to opposite ends of a common frame which is rotatably driven about the cable axis with the cable travelling through the centres of the unwinding and winding heads.

6. Apparatus as claimed in Claim 5, wherein each take-up reel and payoff reel is so supported by its head that its axis lies in a plane radiai to the cable axis.

7. Apparatus as claimed in any one of Claims 4 to 6, wherein the unwinding head lies downstream of the intermediate guide means and the winding head lies upstream of the intermediate guide means.

8. Apparatus as claimed in any one of Claims 4 to 7, wherein the or each take-up reel has, associated with the reel, a traverse mechanism for winding the faulty flexible elongate element in regular layers on the reel.

9. Apparatus as claimed in any one of Claims 5 to 8, wherein the intermediate guide means comprises a tubular die which is supported on the common frame approximately midway between the winding and unwinding heads and through which the cable will travel and, upstream of and downstream of the die, freely rotatable guide pulleys which are also mounted on the common frame.

10. Apparatus as claimed in Claim 9, wherein the tubular die is freely rotatable about its axis and, over an intermediate part of the length of its bore, is so shaped or carries means that will engage in the helical space vacated by a faulty optical cable element.

1 Apparatus as claimed in Claim 10, wherein the intermediate part of the bore of the tubular die has an integral inwardly projecting helical flute or carries a freely rotatable wheel or roller that will engage in and maintain the helical space vacated by a faulty optical cable element.

12. Apparatus as claimed in any one of Claims 4 to 11, wherein the head that is upstream of the intermediate guide means also supports, coaxial with the head, a rotatably driven take-up spool for unwinding from the advancing cable and collecting a binder tape which is helically wound around the cable.

13. Apparatus as claimed in any one of Claims 4 to 12, wherein the head that is downstream of the intermediate guide means also supports, coaxial with the head, at least one rotatably driven carrier for a pad or pads of binder tape to be helically wound around the cable.

14. Apparatus as claimed in Claim 12 or 13, wherein appropriate tape guide means is associated both with the tape take-up spool and with the tape carrier.

1 5. Apparatus as claimed in any one of Claims 5 to 14, wherein the means for causing the cable to travel in a rectilinear direction in the direction of its length comprises at least one pair of endless belts.

16. Apparatus as claimed in Claim 15, wherein the endless belt take-up device or devices, the common frame and the take-up and payoff reels are driven from a common motor through an infinitely variable speed gearbox so that the speed advance of the cable, the rotational speed of the common frame and the rotational speed of the take-up and payoff reels can be inter-related with the length of lay of the helically wound flexible elongate elements of a cable.

17. Apparatus as claimed in Claim 16, wherein means is provided for braking of the take-up and payoff reels relative to the diameter of the flexible element on the reel.

18. Apparatus for use in he manufacture of an optical cable substantially as hereinbefore described with reference to and as shown in the accompanying drawing.

19. A method of manufacturing an optical cable having a faulty optical cable element substantially as hereinbefore described with reference to the accompanying drawing.