The present invention relates to a reel drive apparatus, particularly but not necessarily exclusively for use on a ship. The invention further relates to a cable-unwinding system, to a ship having such a system, to a method of selectively unwinding flexible cable from a reel without at least fully untethering neighbouring reels using such a reel drive apparatus, and to a method of changing a flexible cable to be unwound from a ship into a sea using the said reel drive apparatus.

Submarine cables are used for a wide variety of applications, in particular for power cables, such as windfarm interconnection, cross-channel power distribution and flexible pipes such as flowline and umbilicals connecting subsea well heads and manifolds The cables, pipes, other conduits and/or other flexible elongate elements, are deposited onto the ocean floor using specialist cable and/or pipe layer ships, with the cable and/or pipe to be laid being unspooled from the ship as it travels across the sea. Hereinafter, the term flexible refers to either cable or pipe, as outlined above. The flexible cable and/or pipe to be laid is typically wound onto a large reel, which has a predefined length which can be deposited onto the ocean floor. Once a length of cable and/or pipe has been laid, the crew of the ship will need to switch to another reel of cable and/or pipe in order to continue the laying process. A similar process is required when changing between different types of cable and/or pipe; for example, larger and heavier cables and/or pipes may be required for shallow-water or inland water regions.

The spools or reels are large, with diameters being several times the height of an adult, typically in the region of 10 metres, and are mounted vertically on edge with their rotational axes therefore horizontal. To spool and unspool the reels, a rotary mechanism must be provided in order to lift and rotate the heavy spools, typically being in the order of 40 tonnes to 400 tonnes. This is achieved by providing rails either side of the reel position upon which are mounted movable towers. Each tower has a motor which is engagable with a hub of the reel from either side of the reel, and the towers are capable of engaging with and then lifting the reel away from its reel support in order to permit free rotation of the reel by the motors.

The reels are generally stored on the deck of the ship, upright on the perimeter edges of their end plates, and when not in use, are tethered in position so as to prevent ejection of the reels in rolling seas. Unfortunately, this means that the towers are obstructed by the tethers which maintain the position of the reels, and therefore, in order to position the towers next to a reel to be used, the tethers for adjacent reels must be disconnected in order to allow passage of the towers alongside the adjacent reels. This dramatically increases the time required for the crew to change from one reel to the next, and increases the risk of ejection of an untethered reel in inclement ocean or weather conditions.

Furthermore, cable and/or pipe layer ships are not usually permanently equipped for the task of laying ocean cables and/or pipes, and are instead refitted for a specific project. Every time a particular ship must be used as a cable and/or pipe layer, the reel supports, towers and tower rails must be installed onto the ship, and then removed at the end of the project. As such, there is a large amount of preparatory work which must be undertaken in order to fit a ship for cable and/or pipe laying.

The present invention seeks to provide a simplified way of switching between different reels to be spooled and unspooled on a ship, thereby reducing the modification required to the deck of the ship during outfitting.

According to a first aspect of the invention, there is provided reel drive apparatus for use on a ship to unwind and/or wind flexible cable and/or pipe therefrom into and/or out of water, the reel drive apparatus comprising: a reel having a reel body for storing a flexible cable and/or pipe, and a cable and/or pipe stop at or adjacent to each end of the reel body which projects radially relative to the reel body for axially constraining the flexible cable and/or pipe; a reel support which is mountable to a deck of a ship and on which the reel is seatable in an upright condition for rotation; a reel drive unit which is engagable with the reel and adapted to impart a rotational drive to one side of the reel whilst the reel is mounted on the reel support to wind and/or unwind the flexible cable and/or pipe; and a crane by which the reel drive unit is suspendable at a side of a reel for engagement therewith.

The present arrangement advantageously allows a single reel drive unit to be used to rotate each of the reels onboard a ship using a crane to hoist and suspend the reel drive unit into position. This is a significant improvement over rail-mounted towers as are presently used, firstly because the reel drive unit can be hoisted into position without needing to untether or completely untether adjacent reels, and secondly because cumbersome and awkward rails associated with the towers do not need to be installed on the deck. This not only improves the overall safety on the deck, as reels are less likely to become loose and shift, but also simplifies the of fitting a ship for use as a cable and/or pipe layer. Preferably, the crane may be a ship boom crane, but alternatively may be a static-frame crane.

A wide variety of cranes, preferably being ship-mounted cranes, could feasibly be used in conjunction with the present reel drive apparatus, advantageously allowing the present arrangement to be retrofitted to existing ships without significant alteration to the above- board layout of the ship. Since the existing crane of the ship can be used to hoist the reel drive unit, a wide range of ships could be considered as cable and/or pipe layer ships in the future.

Optionally, the reel support may comprise at least one roller supportably engagable with an edge of the end plates of the reel, in which case, the at least one roller may be freely rotatable.

Permitting free rotation of the reel on the reel support allows the reel drive unit to be engaged with the reel without any or a significant load being imparted to the movable parts of the reel drive unit. This allows for a significant proportion of the structural framework associated with motor towers to be dispensed with, reducing the overall bulk of the apparatus on the deck.

Preferably, the reel drive unit may be engagable with a hub of the reel. In one preferred embodiment, the reel drive unit may comprise a reel engagement head and a motor, the reel engagement head being drivable by the motor. Said reel engagement head may have an outer surface which is complementarily engagable with a portion of the reel. Furthermore, the reel drive unit may include a reel locking means for securing the reel drive unit to the reel in an engaged condition. It is preferable that the reel drive unit complementarily engages with the reel so as to be readily able to impart rotational force thereto without stresses or uneven load; this can be most readily achieved via hub engagement. Locking engagement between the two also ensures that accidental release of the reel drive unit does not occur during tumultuous motion of the ship. The reel drive unit may include a guide leg for aligning the reel drive unit relative to the reel, and said guide leg may be foldable, retractable or collapsible in a storage condition. Furthermore, the reel support may include a locator with which the guide leg is complementarily engagable for aligning the reel drive unit relative to the reel. One of the problems of tower-mounted motor arrangements is that they block the deck of the ship, limiting mobility for the crewmembers. The present reel drive unit is compact and portable, meaning that it can be stowed as a standalone device separately of the rest of the reel apparatus when not in use. The provision of a locator or other suitable an alignment means, such as a guide channel or guide rail, allows for the reel drive unit to be more easily engaged with the reel, which may otherwise be more difficult than that for a tower motor unit given the greater freedom of movement conferred by crane-based hoisting. The locator is primarily beneficial in preventing or limiting back-driving of the reel drive unit, once powered to impart a rotational drive to the reel to which it is engaged.

Preferably, the reel drive unit may be three-dimensionally positionable and alignable when engaged with the crane.

By allowing the reel drive unit to be positioned and aligned, preferably in suspension, in three dimensions above the deck of a ship, a single reel drive unit can be used to drive any of the reels present onboard. This is in stark contrast to the present solution, in which a tower must be engaged from either side of the reel in order to secure and raise the reel before it can be freely rotated to unwind its cable and/or pipe. Similarly, the manoeuvrability of the reel drive unit via the crane removes the need for deck-mounted rails, as are used for the towers, thereby allowing better utilisation of deck space.

According to a second aspect of the invention, there is provided reel drive apparatus for use on a ship to unwind flexible cable and/or pipe therefrom into the sea, the reel drive apparatus comprising: a reel having a reel body for storing a flexible cable and/or pipe, and a cable and/or pipe stop at or adjacent to each end of the reel body which projects radially relative to the reel body for axially constraining the flexible cable and/or pipe; a reel support which is mountable to a deck of a ship and on which the reel is seatable in an upright condition for rotation; a reel drive unit which is engagable with the reel at one side and which is adapted to impart a rotational drive to said one side of the reel whilst the reel is mounted on the reel support to wind and/or unwind the flexible cable and/or pipe; and a drive-unit lifting device by which the reel drive unit is positionable at a side of a reel for engagement therewith.

In this case, the drive-unit lifting device is preferably a crane. However, the drive-unit lifting device may be a track-mounted structure, outboard of a termination point of any tethers, and thus moveable on a fore to aft deck-mounted track.

Preferably, the reel drive apparatus further comprises an engagable locator which, when the reel drive unit is engaged therewith, enables axial movement of the reel drive unit relative to the selected reel and prevents or limits back-driving of the reel drive unit when actuated. In this case, the engagable locator may be a track spur extending from the said fore to aft track and along which the drive-unit lifting device can move to approach a selected reel for engagement. Additionally or alternatively, the engagable locator may be a channel or rail in or on which an anti-rotation element of the drive-unit lifting device is engagable to prevent or limit back-driving. In this latter case, the reel drive unit may be lowered onto the locator, or alternatively may be slid onto the locator. According to a third aspect of the invention, there is provided a cable and/or pipe-unwinding system for a ship to unwind flexible cable and/or pipe therefrom into the sea, the cable and/or pipe-unwinding system comprising: a plurality of reels, each reel having a reel body and an end plate at or adjacent to each end of the reel body which overlaps the said end of the reel body, a flexible cable and/or pipe being storable on the reel body and between the end plates; a plurality of reel supports which are mountable to the deck of a ship and on which the plurality of reels is respectively seatable in an upright condition; a reel drive unit which is engagable with each of the plurality of reels and adapted to impart a rotational drive to the engaged reel whilst mounted on a respective reel support to wind and/or unwind the flexible cable and/or pipe; and a crane on the deck of the ship from which the reel drive unit is suspendable so as to be selectively raisable and/or lowerable into position at or adjacent to each of the plurality of reels.

The provision of a cable and/or pipe unwinding system having a plurality of reels with the crane-mounted reel drive unit allows for the reel drive unit to be hoisted into position in a selective manner so as to avoid tethers or ropes which secure the reels which are not in use. This advantageously improves the overall safety of the deck of the ship, since there is no need to loosen reels which are not in use and could otherwise break free of their confinement.

The system may further comprise a guide on the deck of the ship with which the reel drive unit is engagable for aligning the reel drive unit relative to the reel. Furthermore, the plurality of reel supports may be provided in two parallel rows, the reel drive unit being engagable with each of the plurality of reels from an outward-facing direction of the two parallel rows.

Alignment of the reel drive unit is important, since there is a greater freedom of movement for the reel drive unit when mounted to a crane than when compared with tower-mounted equivalents. The provision of rows or banks of reel supports, with the reel drive unit being engageable with reels thereon from an outside or outboard to inboard direction, allows for the rows to be closely packed together, since in the present invention, there is no need to introduce a drive engagement with a reel other than on one easily-accessible side of a reel.

According to a fourth aspect of the invention, there is provided a ship having a cable and/or pipe-unwinding system in accordance with the second aspect of the invention.

According to a fifth aspect of the invention, there is provided a method of selectively unwinding flexible cable and/or pipe from a reel without at least fully untethering neighbouring reels using a reel drive apparatus, preferably in accordance with the first aspect of the invention, the method comprising the steps of: a] selecting which flexible cable and/or pipe is to be unwound from an associated ship into a sea; b] untethering a corresponding reel on which the selected flexible cable and/or pipe is wound so that the said reel is rotatable on the reel support; c] without requiring at least complete untethering of one or more neighbouring reels, using a crane on the ship to lift and position a reel drive unit for engagement with the untethered reel; and d] with the reel drive unit engaged with the untethered reel, operating the reel drive unit to rotate the untethered reel on the corresponding reel support, thereby enabling the flexible cable and/or pipe to be unwound. Preferably, during step d], the untethered reel may be rotated without being lifted.

According to a sixth aspect of the invention, there is provided a method of changing a flexible cable and/or pipe to be unwound from a ship into a sea using a reel drive apparatus, preferably in accordance with the first aspect of the invention, the method comprising the steps of: a] tethering an untethered reel with which the reel drive unit has been engaged to prevent rotation on its respective reel support; b] untethering a different reel so that the said different reel is rotatable on its respective reel support; c] without requiring at least complete untethering of one or more neighbouring reels, using a crane on the ship to lift and position a reel drive unit for engagement with the untethered reel; and d] with the reel drive unit engaged with the untethered reel, operating the reel drive unit to rotate the untethered reel on the corresponding reel support, thereby enabling the flexible cable and/or pipe to be unwound.

The invention will now be more particularly described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a side view of one embodiment of plurality of reels tethered in place on a plurality of reel supports as part of a reel drive apparatus in accordance with the first aspect of the invention;

Figure 2 shows an end view of the plurality of reels of Figure 1;

Figure 3 shows a perspective representation of one embodiment of a ship having a reel drive apparatus in accordance with the first aspect of the invention mounted onto a deck of the ship;

Figure 4 shows an enlarged perspective representation of the reel drive apparatus of Figure 3;

Figure 5 shows a perspective representation of the reel drive unit of the reel drive apparatus of Figure 3; Figure 6 shows an exploded representation of the reel drive unit of Figure 6;

Figure 7a shows an end view of the reel drive unit of Figure 6;

Figure 7b shows a cross-section along line B-B through the reel drive unit of Figure 7a, indicating a locking mechanism in an unlocked condition;

Figure 7c shows a cross-section along line B-B through the reel drive unit of Figure 7a, indicating the locking mechanism in a locked condition; and

Figure 8 shows a perspective representation of the reel drive apparatus of Figure 4, with the reel drive unit in a plurality of different conditions.

Referring to Figures 1 and 2, there is shown a storage and tethering arrangement, indicated globally at 10, for a plurality of reels 12 upon which flexible cable and/or pipe can be stored. Such a storage and tethering arrangement 10 may be utilised for any planar surface, but is particularly designed for installation onto the deck of a ship.

The reels 10 are massive, typically having a diameter in a range of 5 metres to 15 metres, and more typically having a diameter in a range of 8 metres to 12 metres. More typically, a reel diameter may be approximately 10 metres.

Each reel 12 has a reel body 14, formed here as a tubular element, and an end plate 16 at each end of the reel body 14, each end plate 16 overlapping the end of the reel body 14 in a radial direction so as to act as an axial stop for a flexible cable and/or pipe wound around the reel body 14. Each reel 12 preferably includes a hub 18 at each end of the reel body 14 with which a rotary drive means may be engagable.

Each reel 12 is supported in an upright on-edge condition, whereby perimeter edges of the opposing end plates 16 are engaged with and seated on a reel support 20. The reel support 20 is preferably shaped as a saddle which is complementarily formed to engage with an edge of the end plates 16. The reel supports 20 shown are formed having first and second spaced apart support members 22a, 22b, spaced at a distance which is equal to the length of the reel body 14. It will be appreciated, however, that the reel support 20 could be formed as a unitary support, with one or more bridges joining the first and second support members 22a, 22b, and a cable and/or pipe guide could also be provided associated with the reel support 20 to direct the flexible cable and/or pipe being wound or unwound from the reel 12.

One or more rotation elements, preferably such as wheels, runners, bearings or rollers 24, as shown, may preferably be mounted on or at each of the first and second support members 22a, 22b so as to be contactable with the edge of the end plates 16 of a reel 12 placed thereupon. Such rollers 24 may be freely rotatable to allow the reel 12 to rotate on or at the reel support 20.

Each reel 12 preferably includes a plurality of anchoring points 26 to which tethers or ropes 28 may be secured to prevent the reel 12 from escaping or being dislodged from the reel support 20, particularly under lateral or tumultuous rolling motion which is common at sea. The storage and tethering arrangement 10 shows a typical configuration of tethers 28 overlapping one another to lash a reel 12 in position; a wide variety of tethering arrangements are possible, however. An indicative crewm ember 30 is depicted in Figures 1 and 2 to provide an indication of the relative scale of the reels 12, but this is for illustrative purposes only, and no inference of the actual scale of the reels 12 should necessarily be drawn from the size of the indicative crewmember 30. As can be seen, each reel 12 is tethered from both end plates 16 so as to ensure that it is securely held to the reel support 20. An installed storage and tethering arrangement 10 on a ship 32 is shown in Figures 3 and 4 in combination with a crane 34 and reel drive unit 36 to form a complete reel drive apparatus 38; the tethers 28 are omitted for clarity. The ship 32 comprises a hull 40 having a main deck 42 thereon, upon which is mounted the crane 34. The reel supports 20 are mountable onto the main deck 42 at or adjacent to the crane 34. In the depicted embodiment, each reel support 20 is preferably engaged with a guiding means, here a guide channel 44 which may assist with aligning a drive mechanism for the reel 12 towards the reel support 20; other means could be considered, such as a keyway, rail or buffer which positively engages with the reel drive unit 36, either through slotted engagement or, for example, as a saddle mounting. Such a channel could potentially extend between adjacent reel supports 20 to simplify transition of the reel drive unit 36 between reels 12.

From the crane 34 is suspendable a reel drive unit 36 which is engagable with the hub 18 of each reel 12. In the depicted embodiment, the crane 34 is a ship boom crane having a boom arm 46 and a jib 48 from which a crane line 50 depends. The reel drive unit 36 is engagable with the crane line 50, preferably via a suitably formed crane block. Whilst a ship boom crane is shown, it will be appreciated that a wide variety of crane, hoist or lifting mechanism types are available, particularly on ships, such as rigid frame cranes having movable trolleys, and therefore the depicted crane 34 is for illustrative purposes only. Preferably, however, the lifting means utilised in this embodiment will always enable, preferably by through suspension, an item to be lifted to be maneuvered over more than one reel, to thus be deployed at different sides of the reels. The reel drive unit 36 can be seen in more detail in Figures 5, 6 and 7a to 7c. The reel drive unit 36 has a unit frame 52 which may be used to house or support one or more drive mechanisms, such as the, preferably electric, motor or motors 54 shown. The motor 54 is coupled to a reel engagement head 56 via a slew ring 76 which is here sized so as to be receivably engagable within the hub 18 of a reel 12. The reel drive unit 36 also includes a guide leg 58, which is preferably collapsible, retractable or foldable, and which may have at one end a guide element 60 which is complementarily engagable with the guide channel 44 of the reel support 20. Here, the guide leg 58 is both telescopic, having first and second mutually engagable leg portions 58a, 58b, and foldable, being connected to the unit frame 52 via a movable linkage, such as a pivoting or folding linkage 62 as shown.

The reel engagement head 56 may preferably be provided so as to be tubular, having a tapering cylindrical profile in order to be readily introducible into a hub 18 of the reel 12. The head may have a rivuleted or corrugated outermost circumferential perimeter 64 so as to be able to contact or wedgingly engage with an inner surface of the reel body 14 once introduced to the hub 18. This is particularly effective if complementarily shaped to one or more connectors 66 of the reel body 14, such as those visible in Figure 4. Furthermore, there may preferably be provided one or more apertures 68 in the body of the reel engagement head 56 which allow for the engagement of a locking means.

The components of the locking means can be seen in Figure 6; an actuatable element, such as a pivotable lever 70, cranked arm, or cam element is positioned so as to be engaged with an internal framework 72 of the reel engagement head 56 and actuatable relative thereto. A locking block 74 may then be provided which is engaged with an outer end of the pivotable lever 70. It will be appreciated that the locking block may be any appropriately engagable locking element which will prevent axial disengagement of the reel drive unit 36 from the reel 12. The internal framework 72 may be coupled to the reel engagement head 56, the had 56 coupled to the unit frame 52 via the slew ring 76.

The action of the locking means is shown in Figures 7a to 7c. An unlocked condition is shown in Figure 7b; the pivotable lever 70 is housed within the body of the reel engagement head 56, as is the locking block 74, and therefore the reel drive unit 36 can be simply engaged and disengaged with the reel 12. However, as shown in the locked condition of Figure 7c, the pivotable lever 70 can be actuated, potentially by a screwjack, hydraulic actuator or pneumatic actuator such that the locking block 74 sits external to the perimeter 64 of the reel engagement head 56, thus preventing the reel drive unit 36 from being physically extracted from the hub 18. This may be achieved by providing one or more complementary engagement slots in the hub 18, or a lip on the reel 12 against which the locking blocks 74 abut if extraction of the reel drive unit 36 is attempted.

The process by which the reel drive unit 36 can be positioned is indicated in Figure 8; sequence of positions of the reel drive unit 36 are shown in a single Figure for ease, and are thus referenced as 36a, 36b an 36c.

The reel drive unit 36a in its initial state may be collapsed and stowed on the ship 32 wherever suitable; preferably, the reel drive unit 36a is sufficiently portable, in this case machine portable and not manually portable due to the physical dimensions of the unit, so as to be readily stowable in a standalone condition separately of the remainder of the apparatus for easy access by the crane 34. In a stowed condition, folding linkage 62 is optionally collapsed such that the guide leg 58 is positioned at or adjacent to a planar side of the unit frame 52.

When the reel drive unit 36b is to be used, the crane 34, indicated by crane line 50, can be engaged with the reel drive unit 36b, so as to be lifted ready for engagement with the reel 12. When attached to the crane 36, the reel drive unit 36b is three-dimensionally positionable and alignable, particularly but not necessarily exclusively being able to be manoeuvred over the top of the reels and dropped down into place at one side of a selected reel. In other words, the reel drive unit 36b can be moved by the crane not only in any fore and aft direction, but also in any inboard and outboard direction as well as upwardly and downwardly. This is in contrast to the known prior art tower arrangements presently available, wherein the motor portion is constrained to predefined rails and thus only movable in two dimensions, being along one side of the reels, typically being fore and aft, and then vertically up or down.

In the second deployed condition, the guide leg 58 is folded into a vertical or downwards condition. In a third condition, as shown by reel drive unit 36c, the guide leg 58 has been telescopically extended so as to be in or nearly in contact with the deck 42 of the ship 32 even after raising and/or lowering of the reel drive unit 36c so as to be positioned and aligned with the hub 18 of the reel 12. The reel drive unit 36c can then be manoeuvred towards the reel 12 by the crane 34 such that the guide element 60 of the guide leg 58 engages with the guide channel 44 of the reel support 20.

Preferably, the reel drive unit 36c is manoeuvred into position at or adjacent to the reel 12 from an outboard-facing direction of the reel 12 if more than one parallel row of reel supports 20 is provided. By allowing access to the outboard-facing hubs 18 of the reels 12 using a single reel drive unit 36c, the rows of reel supports 20 can be more tightly packed than would otherwise be the case if access for towers between the rows were to be required.

The reel drive unit 36d may be decoupled from the crane line 50 once engaged with the desired reel 12, with the reel engagement head 56 coupling with the corresponding connectors 66 of the reel 12. With the reel drive unit 36 then connected to an onboard electrical supply if motor driven, or hydraulic or pneumatic drive systems, actuation can take place to enable coupled rotary motion of the reel engagement head 56 and thus reel 12. The locking means is also activated so as to limit the risk of accidental or unintentional decoupling of the reel drive unit 36d and the reel 12 in use. A cable and/or pipe unwinding system for a ship 32 can thus be provided. A plurality of reels 12 and reel supports 20 can be provided on the deck 42 of a ship 32, preferably in two parallel rows. In an initial condition, all of the reels 12 will be tethered in position on the reel supports 20.

When a flexible cable and/or pipe on one of the reels 12 is to be unwound, the selected reel 12 can be untethered. The crane 34 can then collect the reel drive unit 36, raising and/or lowering it into position at or adjacent the reel 12, preferably engaging with the hub 18 thereof. As the reel drive unit 20 is activated for rotation, having engaged with the reel 12, flexible cable and/or pipe will be unwound, and can be fed into the sea off a side of the ship 32. The reel 12, being untethered, is able to freely rotate on the reel support 20 in tandem with the rotation of the reel drive unit 36, releasing flexible cable and/or pipe in the process.

Once the flexible cable and/or pipe on the reel 12 is finished, or if a different flexible cable and/or pipe is required for any reason, then the reel drive unit 36 can be disengaged from the reel 12 and the reel 12 re-tethered. The next reel 12 required can then be untethered, and the crane 34 can hoist the reel drive unit 36 into position without required intermediate reels 12 to be untethered; the crane 34 is able to raise the reel drive unit 36 over and above the tethers 28 and into position without difficulty.

This approach has several advantages over the existing arrangements. Firstly, intermediate reels 12 do not need to be untethered when changing between reels 12 onboard the ship 32, mitigating the risk of unbound reels 12 escaping from their respective supports 20. This is not possible with the present track-mounted towers.

Additionally, only a single reel drive unit 36 is required for all reels 12, since the drive unit 36 can be hoisted to the outer side of any reel 12. At present, towers must be provided on both sides of a reel 12, and towers must be associated with each row of reels 12 on a ship. The present arrangement significantly reduces the infrastructure required to drive a reel 12. Additionally, the provision of the freely rotating parts of the reel supports 20 ensures that the reels 12 do not need to be lifted in order to be driven. The reel drive unit 36 can therefore afford to be less structurally robust compared with the tower arrangement as presently used, since no weight is supported through the reel drive unit 36. It will be appreciated that whilst a hub-driven reel is herebefore described, that a drive mechanism could be considered in which a different point of engagement is used between the reel drive unit and the reel. For example, the reel drive unit could span a diameter of an end plate of the reel, and the drive unit could engage with the edge of the end plate in order to impart drive. Similarly, the reel support need not necessarily be mounted below the reel, and different supports could be considered. For example, a framework could be considered which engages with the rotational axis of the reel, allowing rotation of the reel in a manner akin to that of a Ferris wheel.

It is feasible that the crane could be dispensed with in favour of mounting the reel drive unit on a deck-track. In this case, it is envisaged that a single track could be provided in a fore to aft direction on the deck, preferably to at an outboard side of row of reels and preferably outboard of the furthest tether point terminating on the deck. The reel drive unit can thus be mounted for movement on the track, for example, using a wheeled chassis or support, typically at a height of the hub of each reel and uninhibited by the tethers of the various other reels. Aligned with each reel hub, typically being centrally of each reel support, a track spur extends in an inboard direction of the fore to aft track, typically forming a right-angled offshoot terminating at or adjacent to each reel support. With the selected reel untethered, the track mounted reel drive unit can thus be run along the fore to aft track until the corresponding track spur is reached, and then redirected along the required track spur until the reel drive unit reaches the selected reel. Engagement can then take place between the reel drive unit and the reel hub, as described above in the first embodiment.

As above, the engagement of the reel drive unit with the track spur prevents or inhibits undesirable angular displacement of the reel drive unit during energisation and thus rotation of the coupled reel. The reel drive unit may be height-adjustably mounted on the fore to aft track to enable accommodation of differently sized reels. The height adjustment may be via an integrated lifting mechanism, such as a hydraulic or pneumatic piston or jack apparatus, or may be via an external device, such as the onboard ship crane whereby the required height of the reel drive unit once reached and without the reel drive unit being separated from the track is mechanically fixed using a physical load-bearing pin, brace or lock, thus allowing the crane to be safely decoupled from the reel drive unit and moved away.

However, the use of the fore to aft track, although not impeded by the tethering due to the greater spacing in the outboard direction, does not provide for the degree of flexibility in repositioning the reel drive unit for use with multiple rows of reels. As such, two or more reel drive units would be required for multiple rows of reels requiring access from different sides of the ship. Furthermore, outfitting a ship, due to the requirement of the track or tracks, would take longer and be more costly than the system described in the first embodiment above.

Although the apparatus and system described above is described in reference to laying cables, pipes and other elongate flexible elements or members in a sea, it may be used in any water, including in-shore waterways, lakes, rivers and other bodies of water.

Tethering is referred to above to enable restraining of the reels. However, other restraining means which may also be considered tethering although not or not only via straps may be considered. For example, the reel may be clamped to the support, such as via clamp elements that have a C-shaped profile to allow rotation on the support whilst remaining held in place. The tethering lines may thus be dispensed with. The reel drive unit is preferably freely-manoeuvrable when suspended from the crane or an other lifting device. However, it may be advantageous to tether using tethering lines the suspended reel drive unit to allow some guidance. In this case, one or more guide elements, such as ropes or cables, may be attached to the reel drive unit from, for example, the deck of the ship to allow the reel drive unit to be constrained whilst it is being positioned at or adjacent to the required or selected reel.

It is therefore possible to provide a reel drive apparatus which include a plurality of reels for depositing flexible cable and/or pipe into the ocean under a rotational driving force. The reel drive unit is hoistable using a crane on the ship so as to be able to engage with any of the reels present without needing to unnecessarily untether reels from which flexible cable and/or pipe is not required. This improves the ease with which changeover between reels can be achieved, whilst also improving the safety of the working environment for crewmembers, particularly in rough sea conditions and/or inclement weather.

The words 'comprises/comprising' and the words 'having/including' when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of examples only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined herein.