Splice chamber for wire link to an underwater vehicle

Described herein is a splice chamber for accommodating excess optical cable obtained when making a fusion splice connection between two reels of cable. The chamber comprises two portions which define a space for the optical cable. The chamber is constructed to divide into two longitudinal half portions along a longitudinal line, but each end is retained until conditions are suitable for release. The space inside of the chamber is shaped to determine the bend radius for the enclosed optical cable and protects the cable during storage and handling. When a predetermined force is applied to one end of the chamber, the two longitudinal half portions separate to release the optical cable stored therein, pivoting about the other end.

This application is the US national phase of international application PCT/GB02/05789 filed Dec. 19, 2002, which designated the US and claims priority to GB Application No. 0200354.9 filed 09 Jan. 2002. The entire contents of these applications are incorporated herein by reference.

The present invention relates to improvements in or relating to underwater vehicles.

It is known to use a wire command link to connect an underwater vehicle to its launch platform to provide an exchange of information between the underwater vehicle and the launch platform. The wire command link comprises a copper guide wire which is payed-out from the underwater vehicle as it moves through the water.

The guide wire system consists of two interconnected spools of guide wire, one of which is mounted on the underwater vehicle and the other of which is mounted on the launch platform. The spool of guide wire on the launch platform pays-out through a weighted metal hosepipe which falls, due to gravity, to a position below the launch platform to prevent entanglement of the guide wire with the structure and/or propulsion system of the launch platform. The spool of guide wire on the underwater vehicle unwinds and pays-out from the rear of the underwater vehicle.

Prior to launch of the underwater vehicle, the hosepipe is neatly coiled within a launch tube in the launch platform and is connected by a weak link to the rear of the underwater vehicle which is also located within the launch tube. During the launch phase, the underwater vehicle pulls the hosepipe out of the launch tube until fully deployed, when the weak link separates and the hosepipe falls to a position below the launch platform. The guide wire then pays-out from both spools as the underwater vehicle and the launch platform operate and/or manoeuvre independently.

Whilst copper guide wire is very robust and can be easily jointed and insulated using conventional techniques, there is a move to replace copper guide wire with optical fibres or microcables. Such optical fibres and microcables are, however, quite fragile, and have bend radius limitations. Such optical fibres and cables require a specialised jointing process such as fusion splice techniques.

In fusion splice techniques, lengths of optical fibres or microcables between 0.5 and 1 m are required on each optical fibre or microcable to be available so that the fusion splice technique can be carried out effectively and efficiently. This means that, after the joint has been made, up to 2 m of optical fibre or microcable remains outside the coils of fibre or cable in the underwater vehicle and the launch platform where it is vulnerable to damage due to its fragility.

It is therefore an object of the present invention to provide means for providing storage between the launch platform and the underwater vehicle for the fusion splice joint and any excess fibre or cable. This storage also provides protection for the fusion splice joint during the launch phase.

It is a further object of the present invention to control the bend radius of the optical fibre or microcable to ensure that communication can be maintained between the launch platform and the underwater vehicle and that the fusion splice joint is deployed in a controlled manner during launch of the underwater vehicle.

In accordance with one aspect of the present invention, there is provided a splice chamber for accommodating and protecting a splice and excess optical cable between a launch platform and an underwater vehicle, the chamber comprising:

two half portions joined longitudinally to define a storage chamber;

means for attaching the chamber to the launch platform;

means for attaching the chamber to the underwater vehicle; and

means for separating the two half portions of the chamber.

Advantageously, the storage chamber is shaped to control the bend radius of the optical cable stored therein. Moreover, the storage chamber is also shaped to accommodate twists induced into the optical cable during launch of the underwater vehicle from the launch platform.

The means for separating the two half portions of the chamber may comprise an active release device, for example, a spring-loaded device.

The means for attaching the chamber to the launch platform may comprise a hosepipe, the hosepipe being connected to the chamber by a swivel joint. The means for attaching the chamber to the underwater vehicle may include a weak link and/or the active release device. The weak link may comprise a load-sensitive device, for example, a shear pin located in a retaining collar.

In accordance with the present invention, the splice chamber comprises a double bellmouth chamber which is split longitudinally into two halves. The splice chamber is mounted between the outboard end of a hosepipe connected to a launch platform and to an underwater vehicle. The radius of the bellmouth determines the bend radius of the enclosed optical fibre or microcable.

The attachment point of the splice chamber to the end of the hosepipe contains a spring loaded device which ejects the two halves of the splice chamber when it is possible to do so. The attachment point to the underwater vehicle holds the two halves of the splice chamber closed and incorporates a load sensitive weak link or shear pin.

During the launch sequence, the underwater vehicle pulls the hosepipe out of the launch tube, the load being applied through the load-sensitive weak link or shear pin until the link or shear pin ruptures.

The splice chamber containing the splice and the excess optical fibre or microcable is released from the underwater vehicle and the two halves of the splice chamber are ejected by the spring and fall clear allowing the optical fibre or microcable guide wire to pay out from both the spool in the launch platform and the spool in the underwater vehicle.

Referring initially toFIG. 1, a splice chamber10is shown. The chamber10comprises two portions12,14which when placed together as shown define a space16in which optical fibre or microcable can be stored. The space16has a radius such that, when the optical fibre or microcable is inserted, there is no damage thereof due to bend radius limitations causing the optical fibre or microcable to snap or bend excessively.

Furthermore, the inner surfaces of the two portions12,14are shaped such that a minimum bend radius is maintained while the optical fibre or microcable is entering or leaving the storage space16.

Each portion12,14comprises two half portions12a,12band14a,14brespectively. Portions12a,12bare joined respectively to portions14a,14bat junctions,15a,15bin any appropriate way, for example, by welding.

When deployed, the chamber10divides in two along longitudinal line18to form two identical halves as described below with reference toFIGS. 4 to 8.

Holes20,22,24,26may be provided in the chamber10to reduce weight if required, for example, if the portions12,14are made of steel or other similar material. Holes20,22,24,26also permit visual inspection of the optical fibre or microcable within the chamber10.

Portion12of chamber10has a tapered neck portion25a,25bwhich ends in a lip28a,28bwhich extends over both half portions12a,12bas shown. Similarly, portion14of chamber10has a neck portion27a,27bin which is formed holes29a,29bfor receiving a shear pin as described below. It will be understood that the suffices ‘a’ and ‘b’ refer to the two half portions of the chamber10when divided along longitudinal line18.

FIG. 2illustrates a splice chamber10(shown generally for clarity) connected to a hosepipe30at one end and to an underwater vehicle (not shown in detail) at the other end. A swivel joint32is provided at the end of the hosepipe30to allow relative movement between the splice chamber10and the hosepipe30. A housing34is shaped to partially sit within the swivel joint32and allows unhindered access for the optical fibre or microcable (not shown). The end of the housing34remote from the swivel joint32is attached to an inner housing36by means of pins or screws38. Inner housing36abuts a member40which is biased in position against the action of a spring (not shown for clarity) located in recess42formed between inner housing36and member40. An outer housing44surrounds member40and inner housing36and is connected to inner housing36by screws or pins46. Housing44has a lip48which retains lip28a,28bformed neck portion25a,25bof the splice chamber10.

Neck portion27a,27bof the splice chamber10is connected to a collar50via a shear pin52located in one of holes29a,29b. Also attached to the housing50is a ball joint (not shown) which connects to the underwater vehicle (also not shown).

FIG. 3is similar toFIG. 2and parts which are identical are referenced the same. As before, the splice chamber10is connected to a hosepipe30, via neck portion25a,25band to an underwater vehicle (not shown) at the other end via neck portion27a,27b. A swivel joint32is provided at the end of the hosepipe30. The swivel joint32surrounds an inner housing56which is attached to housing44by means of screws or pins58and supports member40against the action of a spring (not shown for clarity) located in space60. As before, housing44has a lip48which engages lip28a,28bof neck portion25a,25bof splice chamber10. Neck portion27a,27bof the splice chamber10is connected to the underwater vehicle (not shown) via collar50and shear pin52as before.

In both the embodiments ofFIGS. 2 and 3, optical fibre or microcable attached to the launch platform (not shown) via the hosepipe30passes through housing34(FIG. 2) and 56(FIG. 3), through inner housing36(FIG. 2), through member40and into the splice chamber10. Here, the splice and excess optical fibre or microcable left over from the fusion splice operation is stored and protected prior to and during the underwater vehicle deployment. The splice, optical fibre or microcable is wound round the inside of space16and then passes through to the underwater vehicle via neck portion27a,27band ball joint (not shown).

FIGS. 4 to 8illustrate how the splice chamber10is released when it is no longer needed with reference to theFIG. 3embodiment. In each ofFIGS. 4 to 8, the swivel joint32and hosepipe30are not shown.FIG. 4illustrates the prior to hose separation position similar toFIG. 3. As the underwater vehicle moves away from its launch platform, the shear pin52breaks, when the forces are of the correct magnitude, and releases neck position27a,27bof the splice chamber10(FIG. 5). It will be appreciated that collar50with shear pin52retains neck portions27a,27bclosed, and once the pin52breaks, neck portion27a,27bis free to open along line18(FIG. 1) pivoting at the junction of lip28a,28band lip48. As the underwater vehicle moves further away (FIG. 6), the two halves of the splice chamber10move further outwards due to the action of the spring (not shown) in space60) until they are almost free (FIG. 7), and then detach from the housing44(FIG. 8) leaving the housing56, housing44and member40in place.