GB2145580A - Chamber assembly - Google Patents

Abstract

A chamber assembly for submarine repeaters comprises an open-ended tubular housing 1 and two end closure members 2 ,3 providing a lead-through for optical fibre and power cables 9, 10. The internal diameter of the housing is reduced in the vicinity of one end to form an abutment against which one closure member 2 bears in the assembled chamber, entry to the housing for the two closure members and the repeater apparatus 4 being provided by the other end. This arrangement avoids the need to coil excess lengths of cable in the housing. <IMAGE>

Description

SPECIFICATION Chamber assembly The invention relatesto chamber assemblies suit ableforusewith cable mounted equipment in high pressure environments and finds particular application in repeater housing assemblies for use with submarine telecommunications cables.

Repeaters are mounted at breaks in an optical fibre cable spaced at intervalsalongthe length of the cable.

If the cable is for submarine installation, each repeater and its connections to the optical fibre signal elements and power supply elements comprised buy a cable must be provided with protection means capable of withstanding high external pressure. The protection means must also allow access to be obtained to the repeater for purposes such as repair and maintenance.

Conventionally such protection means comprises a substantially symmetrical,tubular housing having a bulkhead at each end in the form of a plug, held in place be removable fastening means. Each bulkhead is adapted to be applied from outside the housing. The high pressureofasubmarineenironmentwhich acts on the outside of the repeater housing when installed has therefore acted in the past as a supplementary factor in keeping the bulkheads in place.

Each bulkhead further provides mountings for power and signal lead through, from the optical fibre cable into the assembled repeater housing. As a result, each bulkhead is effectively attached to the optical fibre cable before the repeater is installed.

Although such repeater housing assemblies have proved satisfactory in use, a disadvantage has been that it has been necessary to accommodate lengths of optical fibre signal elements and power supply elements which are greater than the length of the tubular housing. The excess lengths offibre in the assembly occur because during the installation procedure, one set of optical fibre signal elements and electrical supply elements must be passed through thetubularhousing before being connected tothe repeater. Lengths of each type of element, greater than the length of the tubular housing, musttherefore be left between at least one bulkhead which has been effectively attached to the cable, and the point at which the repeater is to be connected.

Accommodation for the excess lengths has been provided in the past by a chamber adjoining each bulkhead, the excess lengths being coiled therein.

These chambers have necessarily increased the length of the repeater housing assembly, which is rigid, and as a result made handling of the cable at a repeater more difficult. For instance, passage of the cable round a winch drum, often used in bow-laying of cables, is considerably hampered. In the case of optical fibres the need for accommodating excess lengths is also inconvenient because optical fibres are susceptibleto damage when bent.

Afurtherdisadvantage of known repeater housing assemblies has been that, before access can be gained to the repeater apparatus for repair or maintenance purposes, the excess lengths of element have had to be uncoiled to allowthe bulkheadsto be moved apart and the tubular housing to be moved to one side in order to expose the repeater apparatus. This has complicated the requirements for support and protection of cable and repeatercomponentsduring repair and maintenance.

The present invention is intended to provide a repeater housing assembly in which it is not necessary to accommodate lengths of optical fibre and of electrical supply elements which are significantly greaterthan the length ofthe housing, but which is suitable for submarine installation.

The present invention is further intended to provide a repeater housing assembly in which access can be gained to the repeater apparatus, for instance for repair and maintenance purposes, without significant disturbance of the distances between the repeater apparatus and each bulkhead.

According to the present invention there is provided achamberassemblyforuse in protecting repeater apparatus installed at a break in an optical fibre cable from a submarine environment, the assembly comprising an open-ended tubular housing, first and second end closure members, the end closure members being adapted to provide mounting for signal and power lead through from the cabletothe repeater apparatus, and sealing means, wherein the internal diameter ofthe housing is reduced in the vicinity of a first end to form an abutment against which the first end closure member bears in the assembled chamber, entry to the housing for the first end closure member and the repeater apparatus being provided by the second end ofthe housing.

A repeater housing assembly according to the invention will now be described by way of example onlywith referencetotheaccompanying drawings in which: Figure 1 shows a cross-section of a repeater housing assembly installed on an optical fibre cable.

Figure 2 shows part only ofthe repeater housing assembly of Figure 1, in which the sealing arrangements are presented in greater detail.

Figures 3a to 3h show in schematic form the steps involved in installing the repeater housing assembly at a break in an optical fibre cable.

Figure 4 shows in schematic form means to facilitate installation or dismantling of the repeater housing assembly.

Referring to Figure 1, a housingassemblyfora repeater4comprises a substantiallytubularhousing 1, first and second pluglike bulkheads 2, 3 and removable fastening means 5,6,24,25. Each bulkhead 2,3 provides a mounting arrangement7 (notshown in detail)forsignal lead through 9 and power lead through 1 from the cable 8 to the repeater 4. Suitable mounting arrangements are known and are not described below. Sealing means 11,26,28,29 are provided between each bulkhead 2,3 and the tubular housing 1.

The housing assembly also comprises clamping means for securing the ends oftensile load bearing elements of the cable 8 but suitable means are known and are nottherefore described herein.

The internal diameter of the tubular housing 1 is reduced in the vicinity of a first end to form a collar 12.

Afirst bulkhead 2 substantiallyfillsthe aperture surrounded by the collar 12 and extends therefrom to each side ofthe collar 12. The first bulkhead 2 is retained in the aperture by an enlarged head portion 13, and by fastening means 5, which abut opposite sides of the collar 12 and grip ittherebetween. The position ofthefirst bulkhead 2 is such thatthe surface ofthe enlarged head portion 13 provides part ofthe internal surface ofthe repeater housing assembly and the fastening means 5,6 are accessible from outside the assembly. Sealing means 11 is provided between the first bulkhead 2 and the inner periphery ofthe collar 12, and furthersealing means 28 is provided where the enlarged head portion 13 abuts the collar 12.

The fastening means 5,6 comprise an internally threaded ring 5 which co-operates with a thread on the end plug 2 in the manner of a nut and bolt assembly.

The ring 5 has a plurality ofthreaded bores 15 therein, running parallel to its rotational axis. Co-operating screw members 5,6 are positioned in the bores 15, suchthatthe shaft end 18 of each screw member bears against the collar 12.

The internal diameter of the tubular housing 1 is increased in the vicinity of its second end to provide a shoulder 21. The second bulkhead 3 shows an enlarged head portion 23which abutstheshoulder21, via sealing means 29, thereby preventing passage of the second bulkhead 3 into the internal cavity ofthe repeater housing assembly. Further sealing means 26 is provided between the enlarged head portion 23 and the tubular housing 1.

Fastening means 24,25,31 are provided to hold the second bulkhead 3 in place, comprising a ring 24, associated screw members 25 and an end cap 31. The ring 24 is retained in thetubular housing 1, coaxially therewith and adjacent to the bulkhead 3, by means of the end cap 31 which is screw mounted in the end of thetubularhousing 1. Furtherdescription of the end cap 31 is given below. The screw members 25 are positioned in threaded bores 15" in the ring 24 which run parallel to the rotational axis ofthe ring 24. The shaft ends 27 of the screw members 25 bear against the enlarged head portion 23 ofthe second bulkhead 3, thus holding the bulkhead 3 in place.

Referring to Figure2thesealing means 11,26 between the first bulkhead 2 and the inner periphery of the collar 12, and between the second bulkhead 3 and the tubular housing 1, comprise in each case a pair of '0' rings 11 26' seated in peripheral grooves 1", 26" in the bulkhead 2,3. The furthersealing means 28,29 between the enlarged head portions 13,23 ofthe bulkheads 2,3 and the collar 12 and the shoulder 21 respectively, are in the form of Graylok seals.

Thetubularhousing 1 is extended beyond the bulkheads 2,3 and theirfastening means 5,6,24,25 by means ofthe removable end cap 31 and by means of a further removable end cap 30. The bulkheads 2,3 and their fastening means 5,6,24,25 are thereby substantially protected from damage due to contact with the sea bed or other submarine objects, while being easily accessible on removal of the end caps 30, 31. Each end cap 30,31 comprises a short, externally threaded cylinder32with an outwardly turned lip 33.

The threaded cylinder 32 co-operateswith an internal thread nearthe end ofthetubular housing 1 and grub screws 34 applied from the outer surface ofthe tubular housing 1 preventfurther rotation ofthe installed end caps 30,31. The outwardly turned lip 33 lies adjacent to its respective end ofthetubular housing 1, providing the extension thereto.

An advantage ofthe form of seals 1 1, 26 shown.

employing '0' ring pairs 11, is that means may be providedto allowtesting ofthe seals 11,26 before installation ofthe repeater housing assembly in the water. Referring to Figure 2, a shallow peripheral recess 35 is provided in the surface ofthe tubular housing 1 which lies between the grooves 11", 26" in the repeater housing assembly. Access to the recess 35 is provided by a recloseable bore 36. To test the seals 11,26 when the housing is at least partially assembled, grease undera preselected pressure may be used to fill the recess 35. If no grease passes either '0' ring 11 26' the selas 11,26 may be considered sufficient.

In the description below, theterm "first bulkhead" is a member of the type described above as the first bulkhead 2 and theterm "second bulkhead" is a member ofthetype described above as the second bulkhead 3.

Referring to Figure 3, installation ofthe repeater4 and repeater housing assembly at a break in an optical fibre cable comprisesthefollowing steps:- i) Mounting an end cap 30,31 on the optical fibre cable 8to each side of the break (Figure 3a) ii) Mounting fastening means 5,6 associated with a first bulkhead 2 on the optical fibre cable 8 on afirst side ofthe break, between an end cap 30 and the break (Figure 3b) iii) Mountingthetubularhousing 1 the optical fibre cable8 on thefirstside ofthe break, between the fastening means 5,6 and the break (Figure 3c) iv) Installing the first bulkhead 2 on the optical fibre cable 8 between thetubularhousing 1 and the break, which installation includes the mounting arrangement 7 for signal lead through 9 and power lead through lOin the bulkhead 2from the cable 8 to the region ofthe break (Figure3d) v) Installing a second bulkhead 3 preceded by its associated fastening means 24,25,31 on the optical fibre cable 8 on a second sideofthe break, in the same manner regarding signal and power lead through as installation ofthe first.bulkhead 2 (Figure 3e) vi) Mounting the repeater apparatus 4 between the ends of the optical fibre cable 8 at the break, effectively rejoining the ends ofthe cable 8 (Figure 3f) vii) Sliding thetubular housing 1 overthefirst bulkhead 2 into position over the repeater 4 and into engagement with each bulkhead 2,3 (Figure 39) viii) Applying the relevantfastening means 5,6, 24,25,31 to each bulkhead 2,3 (Figure 3h) ixt Fitting each end cap 30,31 in place on the end of thetubularhousing 1 and holding itin position by means of the grub screws 32,33 (Figure 3i) Application of each fastening means 5,6,24,25,3t urges the relevant bulkhead 2,3 into betterengage mentwiththetubularhousing 1.With regard to the first bulkhead 2, tightening the screws in the fastening ring 5 has the effect, once the shaft end 18 of the screws 6 are in contact with the collar 12,of urging the fastening ring 5 away from the collar 12. The first bulkhead 2, being fixedly attached to the fastening 5, is thus urged in the same direction and so further into engagement with the collar 12. With regard to the second bulkhead 3, tightening ofthe screws 25 in the fastening ring 24 has the effect, once the shaft ends 27 ofthe screws 25 are in contact with the bulkhead 3, of urgingthe bulkhead 3 and the fastening ring 24 apart.

Since the fastening ring 24 is retained in the tubular housing 1 by the end cap 31, the bulkhead 3 is thus urged further into engagement with the shoulder 21.

Referring to Figure 3f, to gain access to the repeater apparatus 4for repair or maintenance purposes, it is necessary to undo both end caps 30,31, to disassemblethefastening means 5, 6, 24, 25 between the bulkheads 2,3 and the tubular housing 1, and to slide the tubular housing 1 to one side, over the first bulkhead 2. The repeater apparatus 4 is thus exposed.

Referring to Figure 4, in orderto facilitate gaining access to the repeater apparatus 4 as above, means may be provided to hold each bulkhead 2,3 and the repeater apparatus 4 in a fixed spatial relationship before the tubular housing 1 is installed. Such means may comprise for example rigid longitudinal members 37 which extend between the bulkheads 2,3 and support the repeater apparatus 4 in a fixed position relative to the bulkheads 2,3. By the use of these longitudinal members 37, supportofthe repeater apparatus 4 is provided independently ofthe tubular housing 1 which may therefore be moved into and out of position over equipment constituting a single rigid component.

Claims (8)

1. A chamber assembly, for use in protecting repeater apparatus installed at a break in a telecommunication cablefrom a submarine environment, the assembly comprising an open-ended tubular housing, first and second end closure members, the end closure members being adapted to provide mounting for signal and power lead through from the cableto the repeater apparatus, and sealing means, wherein the internal diameter of the housing is reduced in the vicinityof a first endtoform an abutment against which the first end closure member bears in the assembled chamber, entry to the housing forthe first end closure member and the repeater apparatus being provided by the second end of the housing.

2. A chamber assembly according to claim 1 wherein the internal diameter ofthe housing is increased in the vicinity of the second end to form an abutment against which the second end closure member bears in the assembled chamber.

3. Achamber assembly according to claim 2 wherein the abutment against which the first end closure member bears in the assembled chamber forms one side of a collar construction through which the first end closure member projects, the portion of the end closure member which extends beyond the collarconstruction in an outward direction from the chamber assembly having an external thread which is adapted to co-operate with an internally threaded retaining ring in the manner of a nut and bolt assembly, the retaining ring in co-operation with the collar construction providing fastening means to hold the firstend closure member in place in the assembled chamber

4.A chamber assembly according to claim 3 wherein the retaining ring has a plurality of threaded bores therein, running parallel to the major rotational axis of the ring, through which co-operating screws may be driven such that the shaft end of each screw bears againstthe collar construction thereby exerting a force which acts to separate the retaining ring and the collar construction.

5. Achamber assembly according to claim 4 wherein the housing, in the assembled chamber, extends beyond the second end closure member and is internally threaded in the portion which so extends, a threaded end cap co-operating therewith to provide a stop member against which furtherfastening means, to hold the second end closure member in place in the assembled chamber, may be retained.

6. A chamber assembly according to claim 5 whereinthefurtherfastening meanscomprisesa ring equipped with threaded bores, which bores run parallel tothe major rotational axis of the ring and through which bores co-operating screws may be driven such that the shaft end of each screw bears against the second end closure memberthereby exerting a force which acts to separate the ring and the second end closure member.

7. A chamber assembly according to claim 5 wherein the tubular housing and each end closure member are substantially cylindrical and sealing means are provided between each end closure member and the housing which comprise a pair of'O' rings seated in adjacent grooves, which grooves lie in substantially parallel planes and are constructed in the surface of each end closure memberwhich abuts the inner curved surface of the housing.

8. A chamber assembly substantially as described hereinbefore, with reference to the accompanying figures.