Patent Description:
Vessels such as tugboats have engines that typically produce <NUM> to <NUM>,<NUM> kW (~ <NUM> to <NUM>,<NUM> hp).

<CIT> discloses a single and multi-engine drive system for a twin screw vessel. <CIT> discloses a ship propulsion device. <CIT> discloses improvements in or relating to ice-breaker vessels. <CIT> discloses a ship propulsion device with at least two motors for driving two variable pitch propellers. <CIT> discloses a ship's propulsion system. <CIT> discloses Fuel economizing drive system for naval and merchant ships.

Tugboats can have different types of propulsors for their method of propulsion. Some tugboats have two propulsors such as azimuthing thrusters to provide thrust. If an engine failure occurs, then the inoperative azimuthing thruster can produce a big drag load. If this happens close to shore when heading back to a harbor, the problem could be minor. However, if the tugboat or vessel is in operation or far away from shore, any failure of the engine could become a serious problem.

Tugboats can be massively over engineered to provide very high peak loads. In most operations, for example during free sailing, maximum peak load is not required by the engine. It may be desirable to have a system that minimizes running hours on the engines as well as increasing the load on the engine in operation and therefore only running low load when sailing between two locations.

Furthermore, in some circumstances it may be advantageous to have a system that can flexibility in the operation of the tugboat engines.

Examples of the present invention aim to address and overcome fully or at least partly the aforementioned problems.

The present invention provides a linking drive system coupling together a first drivetrain and a second drivetrain of a vessel the first drivetrain for connecting a first prime mover and a first propulsor, the first drivetrain comprising a first drive shaft, the second drivetrain for connecting a second prime mover and a second propulsor, the second drivetrain comprising a second drive shaft; , the linking drive system comprising: a linking drive clutch, the linking drive clutch comprising at least a first clutch part and a second clutch part which are engageable with each other and can transmit rotation therebetween; at least one flexible drive link coupled between the linking drive clutch and the first and / or second drivetrains, wherein the at least one flexible drive link is coupled between the linking drive clutch and the first and / or second drive shafts; wherein the linking drive clutch is engageable to allow rotation of one of the first and second drive shafts, generated by a respective one of the first and second prime movers, to be transferred to the other of the first and second drive shafts; characterised in that the linking drive system comprises: at least a first flexible drive link, the first flexible drive link being coupled between the first drive shaft and the first clutch part of the linking drive clutch; and at least a second flexible drive link coupled between the second drive shaft and the second clutch part of the linking drive clutch.

In an example, the linking drive system may comprise a chain drive or a belt drive.

In an example, the at least first and second flexible drive links may be coupled to the first and second drive shafts on a prime mover side of a main drive clutch.

In an example, the at least first and second flexible drive links may be coupled to the first and second drive shafts on a propeller side of a main drive clutch.

In an example, the at least first and second flexible drive links may be coupled to the first and second drive shafts on a linking drive clutch side of a hydraulic pump of the propulsor such that the hydraulic pump can operate a slew of the propulsor when the linking drive clutch is engaged.

In an example, the linking drive system may comprise a linking drive clutch controller configured to control the engagement of the first clutch part and the second clutch part.

In an example, the linking drive system may comprise a sensor for detecting a rotation of at least one of the first and second drive shafts, the first and second flexible drive links or the first clutch part and the second clutch part.

In an example, the linking drive clutch controller may be configured to activate the engagement of the first clutch part and the second clutch part when there is no relative rotation, or below a pre-defined threshold rotation.

In an example, the linking drive clutch may be an electromagnetic clutch.

In an example, the linking drive system may be a chain drive system and the chain drive system comprises at least a first sprocket and a second sprocket, wherein the first sprocket is coupled to the first drive shaft and the second sprocket is coupled to the second drive shaft, and the at least first and the at least second flexible drive links are chains.

In an example, the chains may be each enclosed in a chain box.

In an example, the chain box may comprise a reservoir or a spraying device for lubricating the chains.

In an example, the linking drive system may comprise at least one diverter sprocket, the diverter sprocket is arranged such that the direction of at least a portion of the chain is diverted.

In another aspect of the invention there is provided a vessel comprising a drive system according the previous aspect.

In an example, the vessel according may be a tugboat.

In another aspect of the invention there is provided a linking drive kit mountable on a vessel drive system for coupling together a first drivetrain and a second drivetrain of a vessel, the linking drive kit comprising: a linking drive clutch, the linking drive clutch comprises at least a first clutch part and a second clutch part which are engageable with each other and can transmit rotation therebetween; at least a first chain coupled between the first drivetrain and the first clutch part, wherein the first chain is coupled between a first drive shaft of the first drivetrain and the first clutch part of the linking drive clutch, the first drivetrain connecting a first prime mover and a first propulsor; and at least a second chain coupled between the second drivetrain and the second clutch part, wherein the second chain is coupled between a second drive shaft of the second drivetrain and the second clutch part of the linking drive clutch, the second drivetrain connecting a second prime mover and the second propulsor; wherein the linking drive clutch is engageable to allow the rotation of one of the first and second drive shafts, generated by a respective one of the first and second prime movers, to be transferred to the other of the first and second drive shafts.

The invention will, for simplicity, be explained throughout the application in relation to a vessel, namely at tugboat. However, in other examples, the vessel can be any other types of vessel that have at least two prime movers and each prime mover having at least one propulsor associated therewith. For example, the vessel can be a platform supply vessel, an anchor handler, a ferry, a barge, a container ship, a tanker, a fishing boat, a cruise ship, a yacht or any other type of vessel. Hereinafter, the term "tugboat" will be used, but the tugboat can be any type of vessel.

<FIG> shows a perspective view of an example of a vessel such as a tugboat <NUM> having propulsors <NUM>, <NUM>. The tugboat <NUM> is for assisting a marine vessel, such as a container ship, to maneuver. Operation of the tugboat <NUM> for maneuvering a container ship is known and will not be discussed in further detail.

The tugboat <NUM> includes a hull <NUM> and fenders <NUM>. In other examples of the tugboat <NUM>, the fender <NUM> could be omitted. The tugboat <NUM> also has a deck <NUM> and a wheelhouse <NUM> mounted on the deck <NUM> and /or the hull <NUM>.

The tugboat <NUM> comprises a plurality of propulsors <NUM>, <NUM> for providing propulsion to the tugboat <NUM>. <FIG> shows a single propulsor <NUM>, but further propulsors may be provided. In some examples, the propulsor <NUM> is an azimuth thruster <NUM>. In some examples, the tugboat <NUM> normally has two propulsors <NUM>, <NUM>. In some examples, the plurality of propulsors <NUM>, <NUM> are azimuthing thrusters which can rotate about a vertical axis to direct thrust in a plurality of directions. Some azimuthing thrusters are azimuthing podded drives which are also known as "azipods". Hereinafter, azimuthing podded drives will be referred to as azimuth thrusters. The second propulsor <NUM> (not shown in <FIG> but shown in <FIG>) is located adjacent and parallel to the first propulsor <NUM>.

In an example, the at least one propulsor <NUM>, <NUM> is one or more of: a propeller, a thruster, a rudder propeller, an electric rudder propeller, a fixed pitch propeller, a variable pitch propeller, an azimuthing thruster, a water jet propulsor, or an azimuthing podded drives thruster. In another example, the at least one propulsor <NUM>, <NUM> are bow thrusters. Yet another example, the at least one propulsor <NUM>, <NUM> are stem thrusters. In an example, at least one propulsor <NUM>, <NUM> are azimuthing podded drives. In some examples, the at least one propulsor <NUM>, <NUM> are propellers. In an example, the at least one propeller <NUM>, <NUM> is a fixed or variable pitch propeller. In an example, at least one propulsor <NUM>, <NUM> is a plurality of propulsors comprising a combination of two or more of: a propeller, a thruster a rudder propeller, an electric rudder propeller, a fixed pitch propeller, a variable pitch propeller, an azimuthing thruster, a water jet propulsor, or an azimuthing podded drives. In yet other examples, the at least one propulsor <NUM>, <NUM> can be any means suitable for providing propulsion to the tugboat <NUM>.

An example of a configuration of a first propulsion drivetrain system <NUM> for the first propulsor <NUM> is illustrated in <FIG> illustrates a schematic side view of the first propulsion drivetrain system <NUM> for a vessel comprising two propulsors, <NUM>, <NUM>.

<FIG> discloses the first propulsion drivetrain system <NUM> comprising the first propulsor <NUM> and a first prime mover <NUM>. The first propulsor <NUM> is coupled to and driven by a first prime mover <NUM>. In some examples, the first prime mover <NUM> can be a diesel engine, electrical motor, or a diesel-electric hybrid system. The diesel engine can be a <NUM>-stroke diesel engine or a <NUM>-stroke diesel engine. In other examples, the first prime mover <NUM> is an internal combustion engine that can burn any type of fossil fuel. In some examples, the first prime mover <NUM> can be any suitable means for powering the first propulsor <NUM>.

The first propulsor <NUM> and the first prime mover <NUM> are coupled together by a first drivetrain <NUM>. The first drivetrain <NUM> comprises a first drive shaft <NUM> having a first and second part 23a, 23b connected to the first prime mover <NUM>. In some examples, the first drivetrain <NUM> comprises one or more gearboxes and clutches for transmitting drive from the first prime mover <NUM> to the first propulsor <NUM>. In some examples, the first drivetrain <NUM> comprises a first main drive clutch <NUM>. The first main drive clutch <NUM> is configured for selectively engaging the first prime mover <NUM> to the first propulsor <NUM>.

The first part 23a of the first drive shaft <NUM> is connected between the first prime mover <NUM> and a first main drive clutch <NUM>. The second part 23b of the first drive shaft <NUM> is connected between the first main drive clutch <NUM> and the first propulsor <NUM>.

The second propulsor <NUM> will have a similar propulsion drivetrain system <NUM> to the first propulsion drivetrain system <NUM>. The second propulsion drivetrain system <NUM> will now be described with reference to <FIG> illustrates a schematic side view of the second propulsion drivetrain system <NUM> for a vessel comprising two propulsors, <NUM>, <NUM>.

<FIG> discloses second propulsion drivetrain system <NUM> comprising the second propulsor <NUM> and a second prime mover <NUM>. The second propulsor <NUM> is coupled to and driven by a second prime mover <NUM>. Similar to the first propulsion drivetrain system <NUM>, in some examples, the second prime mover <NUM> can be a diesel engine, electrical motor, or a diesel-electric hybrid system. The diesel engine can be a <NUM>-stroke diesel engine or a <NUM>-stroke diesel engine. In other examples, the second prime mover <NUM> is an internal combustion engine that can burn any type of fossil fuel. In some examples, the second prime mover <NUM> can be any suitable means for powering the second propulsor <NUM>.

The second propulsor <NUM> is coupled together by a second drivetrain <NUM>. The second drivetrain <NUM> comprises a second drive shaft <NUM> having a first and second part 33a, 33b connected to the first prime mover <NUM>. In some examples, the second drivetrain <NUM> comprises one or more gearboxes and clutches for transmitting drive from the second prime mover <NUM> to the second propulsor <NUM>. In some examples, the second drivetrain <NUM> comprises a second main drive clutch <NUM>. The second main drive clutch <NUM> is configured for selectively engaging the second prime mover <NUM> to the second propulsor <NUM>.

The first part 33a of the second drive shaft <NUM> is connected between the second prime mover <NUM> and a second main drive clutch <NUM>. The second part 33b of the second drive shaft <NUM> is connected between the second main drive clutch <NUM> and the second propulsor <NUM>. In other examples of the first and second drivetrain systems <NUM>, <NUM>, the first and second main drive clutches <NUM>, <NUM> could be omitted and the first and second propulsors <NUM>, <NUM> are respectively directly connected to the first and second prime mover <NUM>, <NUM>.

Now turning to <FIG>, the tugboat <NUM> will be discussed in further detail. <FIG> discloses a schematic cross-sectional top view of a tugboat <NUM> having two propulsors <NUM>, <NUM> and a linking drive system <NUM>. The linking drive system <NUM> is selectively engageable for transmitting drive between the first and second drivetrain systems <NUM>, <NUM> of the tugboat <NUM>. In this way, drive can be transmitted from the first prime mover <NUM> to the second propulsor <NUM>. Alternatively, drive can be transmitted from the second prime mover <NUM> to the first propulsor <NUM>. In some examples, the linking drive system <NUM> can comprise at least one chain drive, or a belt drive. In other examples, the linking drive system <NUM> can be any suitable drive means for providing drive between the first and second drive shafts <NUM>, <NUM>.

The linking drive system <NUM> further comprises a linking drive clutch <NUM> for selectively coupling the drive between the first and second drive shafts <NUM>, <NUM>. The linking drive clutch <NUM> comprises at least a first clutch part <NUM> and second clutch part <NUM> which are engageable with each other and can transmit rotation therebetween. Either the first or second prime mover <NUM>, <NUM> can provide drive to both the first and second propulsors <NUM>, <NUM> via the linking drive system <NUM>. Accordingly, the first clutch part <NUM> can drive the second clutch part <NUM>. Alternatively, the second clutch part <NUM> can drive the first clutch part <NUM>. As shown in <FIG>, the linking drive clutch <NUM> is mounted between the first and second drive shafts <NUM>, <NUM>. In other examples, the linking drive clutch <NUM> can be mounted on either the first or second drive shaft <NUM>, <NUM>. In this example both of the first clutch part <NUM> and second clutch part <NUM> are mounted on e.g. the first drive shaft <NUM>. In this way, a single flexible drive link <NUM> is used to couple the drive between the first and second drive shafts <NUM>, <NUM>.

The first clutch part <NUM> and second clutch part <NUM> are selectably moveable between a first position in which the first clutch part <NUM> and second clutch part <NUM> are not in physical engagement and no rotation is transmitted and a second position in which the first clutch part <NUM> and second clutch part <NUM> are in physical engagement and rotation is transmitted therebetween. The linking drive clutch <NUM> can be any type of clutch such as a slip clutch, a non-slip clutch, a mechanical or an electromagnetic clutch. The linking drive clutch <NUM> can also be operable remotely, e.g. from the wheelhouse <NUM> of the tugboat <NUM>.

The linking drive system <NUM> further comprises at least a first flexible drive link <NUM>. The first flexible drive link <NUM> is coupled between the first drive shaft <NUM> and the first clutch part <NUM> of the linking drive clutch <NUM>. The linking drive system <NUM> also comprises at least a second flexible drive link <NUM>. The second flexible drive link <NUM> is coupled between the second drive shaft <NUM> and the second clutch part <NUM> of the clutch <NUM>. By using the linking drive system <NUM> and having the above configuration, the rotation from one of the first and second drive shafts <NUM>, <NUM> can be transferred to the other of the first and second drive shafts <NUM>, <NUM> when the linking drive clutch <NUM> is engaged. In this way, when the linking drive clutch <NUM> is engaged, the first and second drivetrains <NUM>, <NUM> are linked. This means that a single prime mover <NUM>, <NUM> (e.g. the first or the second prime mover <NUM>, <NUM>) can drive both the first and second propulsors <NUM>, <NUM>. Advantageously if one of the prime movers <NUM>, <NUM> is inoperable, the other prime mover <NUM>, <NUM> can power the first and second propulsors <NUM>, <NUM>.

In an example, the linking drive system <NUM> is a chain drive system <NUM> in which the first flexible drive link <NUM> and the second flexible drive link <NUM> are a first and a second drive chain <NUM>, <NUM>. The chain drive system <NUM> will be described briefly turning to <FIG> and <FIG>. <FIG> shows a schematic cross-sectional side views of a first sprocket <NUM> connected to at least one flange <NUM> e.g. first and second flanges 28a, 28b of the first drive shaft <NUM>. In an example, the linking drive system <NUM> comprises a first and second sprockets <NUM>, <NUM> respectively mounted on the first and second drive shafts <NUM>, <NUM>. <FIG> only shows the first drive shaft <NUM>, but the second sprocket <NUM> is mounted to the second drive shaft <NUM> in the same way as shown in <FIG>. The first and second sprockets <NUM>, <NUM> mesh with the first and second drive chains <NUM>, <NUM>. The first and second sprockets <NUM>, <NUM> can be attached to the first and second drive shafts <NUM>, <NUM> in different ways which will be discussed in further detail below with respect to <FIG>. Similarly, the first clutch part <NUM> and second clutch part <NUM> respectively comprise first and second clutch sprockets 49a, 49b (as best shown in <FIG>) for meshing with the first and second drive chains <NUM>, <NUM>.

As mentioned above, the second part 23b of the first drive shaft <NUM> connects between the first main drive clutch <NUM> and the first propulsor <NUM>. In an example, the first sprocket <NUM> is mounted on the second part 23b of the first drive shaft <NUM> outputted from the first main drive clutch <NUM>. In other examples, the first sprocket <NUM> and the second sprocket <NUM> can be mounted at any position on the first and second drive shafts <NUM>, <NUM>.

The first and second flexible drive links <NUM>, <NUM> can easily be directed around any existing parts of the tugboat <NUM> which allows for easier installation of the linking drive system <NUM>. Existing parts could be pipes for water, hydraulics, fuel, or sensors or any other already existing installation in the tugboat <NUM>. Advantageously, this means that retrofit of the linking drive system <NUM> can mounted on existing drivetrain systems of a tugboat <NUM>.

Furthermore, the linking drive system <NUM> being a chain drive or a belt drive will advantageously mean that the first and second drive shafts <NUM>, <NUM> will rotate in the same direction. This means that the linking drive system <NUM> can be simple and does not require additional gearboxes for reversing the rotation of e.g. linking transmission drive shafts between the first and second drive shafts <NUM>, <NUM>.

Some examples of different configurations for the first and second flexible drive links <NUM>, <NUM> will be further discussed in relation to <FIG> show a schematic view of different layouts of the first and second flexible drive links <NUM>, <NUM> of the linking drive system <NUM>.

For example, the linking drive system <NUM> is mounted in the tugboat <NUM> such that first and second flexible drive links <NUM>, <NUM> take a path which is a "V shape". The linking drive clutch <NUM> is mounted in the centre of the V shape, illustrated in <FIG>.

In some alternative examples, the linking drive system <NUM> is mounted in the tugboat <NUM> such that the first and second flexible drive links <NUM>, <NUM> take a path which is a "U shape".

The linking drive clutch <NUM> is mounted with the linking drive clutch <NUM> in the centre of the U shape, illustrated in <FIG>.

Also illustrated in <FIG> are additional linking diverter sprockets <NUM>, <NUM> for forming the U shape. The shape or path of the first and second flexible drive links <NUM>, <NUM> can be customized in any way with first and second linking diverter sprockets <NUM>, <NUM>. In some examples, there can be any number of linking diverter sprockets <NUM>, <NUM>. <FIG> show two exemplary paths for the linking drive system <NUM>, but in other examples there can be any number of flexible drive links <NUM>, <NUM> and linking diverter sprockets <NUM>, <NUM> to guide the linking drive system <NUM> along any shaped path. In some examples, the number of linking diverter sprockets <NUM>, <NUM> are selected depending on how many turns around existing components in the tugboat <NUM> is needed.

In some examples, the first and second flexible drive links <NUM>, <NUM> are both single chain loops. However, in other examples, the first and / or the second flexible drive links <NUM>, <NUM> comprise a plurality of chain loops. For example, the first and second flexible drive links <NUM>, <NUM> are separated in to many smaller flexible drive links along a desired path.

Turning to <FIG>, this will be discussed in further detail. For example, the U shape illustrated in <FIG> could comprise four flexible drive links 25a, 25b, 35a, 35b. A first flexible drive link 25a is connected between the first drive shaft <NUM> and the first linking diverter sprocket <NUM>. A second flexible drive link 25b is connected between the second linking diverter sprocket <NUM> and the linking drive clutch <NUM>. A third flexible drive link 35b is connected between the linking drive clutch <NUM> and the second linking diverter sprocket <NUM>. A fourth flexible drive link 35b is connected between the second linking diverter sprocket <NUM> and the second drive shaft <NUM>. The flexible drive links <NUM>, <NUM> are designed to be of a size and material that can withstand any effect on the first and second drive shafts <NUM>, <NUM> produced by the prime movers <NUM>, <NUM> and that is to be transferred to the other drive shaft <NUM>, <NUM>.

In some examples as mentioned above, the flexible drive links <NUM>, <NUM> are a chain. The chain comprises a plurality of chain link pieces (not shown for the purposes of clarity).

At least one of the chain link pieces is a removeable chain link piece. The removeable chain link piece can be disassembled and permits the flexible drive links <NUM>, <NUM> to be removed from the linking drive system <NUM>. This permits replacement or maintenance of the chain. In some examples, each chain link piece is separable from immediately adjacent chain link piece. This means that if one or more chain link pieces break during operation, one or more chain link pieces can be removed and / or replaced. In this way, using a chain for the flexible drive links <NUM>, <NUM> for the linking drive system <NUM> increases the ease of maintenance and repair. Since at least one or more chain link pieces are separable, this means that the first and second drive shafts <NUM>, <NUM> do not have to be removed during replacement of the chain.

Alternatively, as mentioned above, the flexible drive links <NUM>, <NUM> are belts (not shown). In this case, the belts are a unitary loop of material. In order to replace the belt, the first and second drive shafts <NUM>, <NUM> have to be removed during replacement of the belt. Optionally back up replacement belts can be initially positioned around the first and second drive shafts <NUM>, <NUM> and moved into engagement with the linking drive system <NUM> when needed (e.g. a belt snaps during operation).

The linking drive system <NUM> further allows for powering and driving the first and second propulsors <NUM>,<NUM> if one of the prime movers <NUM>, <NUM> fails. For example, if the first prime mover <NUM> fails, then linking drive clutch <NUM> is engaged allowing the rotation of the second drive shaft <NUM> generated by the second prime mover <NUM> to be transferred to the first drive shaft <NUM>. Thus, the second prime mover <NUM> drives both propulsors <NUM>, <NUM>. Similarly, if the second prime mover <NUM> fails, then linking drive clutch <NUM> is engaged allowing the rotation of the first drive shaft <NUM> generated by the first prime mover <NUM> to be transferred to the second drive shaft <NUM>. In some examples, the linking drive system <NUM> is configured to transfer 400kW between the first and second drive shafts, <NUM>, <NUM>. In some examples, this is enough power to allow free sailing of the tugboat <NUM> without a bollard pull e.g. a towing container ship. In some examples, 300kW-500kW is transferred between the first and second drive shafts <NUM>, <NUM>. In some other examples, 100kW-700kW is transferred between the first and second drive shafts <NUM>, <NUM>. In some other examples, 100kW-1500kW is transferred between the first and second drive shafts <NUM>, <NUM>.

Turning back to <FIG>, the linking drive system <NUM> will be discussed in further detail. <FIG> shows an example wherein the at least first and second flexible drive links <NUM>, <NUM> are coupled to the first and second drive shafts <NUM>, <NUM> between the first and second main drive clutches <NUM>, <NUM> and the first and second propulsors <NUM>, <NUM>. In this way, the first and second main drive clutches <NUM>, <NUM> are between the first and second prime movers <NUM>, <NUM> and the linking drive system <NUM>. In some examples, the first and second main drive clutches <NUM>, <NUM> can be respectively integral with the first and second propulsors <NUM>, <NUM>. That is, the first and second main drive clutches <NUM>, <NUM> are mounted within the housing (not shown) of the first and second propulsors <NUM>, <NUM> e.g. an azimuthing thruster. Alternatively, <FIG> schematically represents that the first and second main drive clutches <NUM>, <NUM> are separate components from the first and second propulsors <NUM>, <NUM>.

In some types of propulsors <NUM>, <NUM> hydraulic pumps (not shown) are used to control the slew of the propulsor <NUM>, <NUM> and the power to drive the hydraulic pumps is taken from the first and / or the second drive shafts <NUM>, <NUM> connected to the propulsor <NUM>, <NUM>. Therefore, if the first and second flexible drive links <NUM>, <NUM> are arranged as in <FIG> and described above, also the hydraulic pumps will be powered all the time, even if one of the first or second prime movers <NUM>, <NUM> fail.

In some examples, the flexible drive links <NUM>, <NUM> are positioned between the first or second propulsors <NUM>, <NUM>. In this case, if the drive is transmitted between directly between the first or second propulsors <NUM>, <NUM>, then the hydraulic pump is positioned between the linking drive system <NUM> and the first and second main drive clutches <NUM>, <NUM>. In this less preferred example, the hydraulic drive does not receive power from the first or second drive shafts <NUM>, <NUM>.

Another example will now be described in reference to <FIG> shows a schematic cross-sectional top view of the tugboat <NUM> having the first and second propulsors <NUM>, <NUM> and the first and second flexible drive links <NUM>, <NUM> coupled to the first and second drive shafts <NUM>, <NUM> between the first and second prime movers <NUM>, <NUM> and the first and second main drive clutches <NUM>, <NUM>.

By having the first and second flexible drive links <NUM>, <NUM> coupled in this way to the first and second drive shafts <NUM>, <NUM>, it is possible to use separate first and second propulsors <NUM>, <NUM> and first and second main drive clutches <NUM>, <NUM> compared to an integrated first and second propulsor <NUM>, <NUM> and first and second main drive clutch <NUM>, <NUM> arrangement (as mentioned above with respect to <FIG>). In an example, the linking drive clutch <NUM> and the first and second flexible drive links <NUM>, <NUM> are designed to withstand the full torque of the prime movers <NUM>, <NUM>. In an example, the linking drive clutch <NUM> and the first and second flexible drive links <NUM>, <NUM> are designed to withstand the full torque of the prime movers <NUM>, <NUM>.

In an example, the linking drive system <NUM> comprises a clutch controller <NUM>, illustrated in <FIG> illustrates a schematic cross-sectional top view of the tugboat <NUM> having the first and second propulsors, <NUM>, <NUM>, the linking drive system <NUM> comprising the linking drive clutch <NUM> and the clutch controller <NUM>. The clutch controller <NUM> is, in an example, configured to control the engagement of the first clutch part <NUM> and second clutch part <NUM> of the linking drive clutch <NUM>. The clutch controller <NUM> remotely and/or autonomously controls the linking drive clutch <NUM> from e.g. the wheelhouse <NUM> or another place on the tugboat <NUM>.

<FIG> shows an example with least one rotation sensor <NUM>. In some examples, the rotation sensor <NUM> determines a relative rotation between one or more parts of the first propulsion drivetrain system <NUM> and the second propulsion drivetrain system <NUM>. For example, the rotation sensor <NUM> determines a rotation direction and/or speed of rotation of at least one of the first or second drive shafts <NUM>, <NUM>, the first or second flexible drive links <NUM>, <NUM> or the first clutch part <NUM> and second clutch part <NUM> of the linking drive clutch <NUM>. In some examples, the rotation sensor <NUM> is mounted adjacent on the first clutch part <NUM> and detects relative movement of the second clutch part <NUM> with respect to the first clutch part <NUM>.

In <FIG>, the rotation sensor <NUM> is arranged at the first and second clutch parts <NUM>, <NUM>. In some examples, the rotation sensor <NUM> is placed at the first or second drive shaft <NUM>, <NUM>, or at the first or second flexible drive links <NUM>, <NUM>. In an example, several rotation sensors <NUM> are used to detect the rotation of several of the first or second drive shafts <NUM>, <NUM>, the first or second flexible drive links <NUM>, <NUM> or the first and second clutch parts <NUM>, <NUM> of the linking drive clutch <NUM>. The rotation sensor <NUM> can e.g. be an optical sensor, magnetic sensor, hall-effect sensor, inductive sensors, oscillatory sensor, magnetoresistive sensor or eddy current sensors. The clutch controller <NUM> and the rotation sensor <NUM> are connected to each such that a signal resulting from any detected rotation direction and/or speed of rotation from the rotation sensor <NUM> is sent to the clutch controller <NUM>, illustrated in <FIG> shows a schematic view of the clutch controller <NUM> connected to the rotation sensor <NUM> and the linking drive clutch <NUM>. The connection between the clutch controller <NUM> and the rotation sensor <NUM> can be e.g. wired and/or wireless.

In an example, the clutch controller <NUM> is configured to activate the engagement of the first and second clutch parts <NUM>, <NUM> of the linking drive clutch <NUM>. In some examples, the clutch controller <NUM> comprises an actuator (not shown) for moving the first clutch part <NUM> and second clutch part <NUM> between the first position in which the first clutch part <NUM> and second clutch part <NUM> are not in physical engagement and no rotation is transmitted and a second position in which the first clutch part <NUM> and second clutch part <NUM> are in physical engagement and rotation is transmitted therebetween. In some examples, the clutch controller <NUM> is configured to actuate the linking drive clutch <NUM> when a differential rotation is zero between the first clutch part <NUM> and second clutch part <NUM>. In another example, the clutch controller <NUM> is configured to engage the first clutch part <NUM> and second clutch part <NUM> below a pre-defined threshold of speed of the differential rotation. In some examples, the threshold is below <NUM> revolutions per minute(rpm), <NUM> rpm or <NUM> rpm.

In some examples, the clutch controller <NUM> is configured to automatically control the linking drive clutch <NUM>, illustrated in <FIG> shows a flowchart of a method <NUM> for controlling the linking drive clutch <NUM> by the clutch controller <NUM>. In this way, the clutch controller <NUM> can act independently and quickly based on e.g. input from the rotation sensor <NUM>. In some examples, the engagement between the first clutch part <NUM> and second clutch part <NUM> is actuated by the operator of the tugboat <NUM>. However, the clutch controller <NUM> prevents the operator of the tugboat <NUM> engaging the linking drive clutch <NUM> when it is unsafe to do so. For example, when the first clutch part <NUM> and second clutch part <NUM> are moving relative to each other and will damage each other if the first clutch part <NUM> and second clutch part <NUM> physically engage each other.

In some examples, the clutch controller <NUM> is configured to actuate and selectively engage the first clutch part <NUM> and second clutch part <NUM> of the linking drive controller <NUM>. The method <NUM> comprises the step of detecting a speed and/or direction of rotation <NUM> of least one of the first or second drive shafts <NUM>, <NUM>, the first or second flexible drive links <NUM>, <NUM> or the first clutch part <NUM> and second clutch part <NUM> of the linking drive clutch <NUM>. The method further comprises the step of determining <NUM>, if the speed of rotation is below a pre-defined threshold, zero or in a same direction. Lastly, the method comprises the step of activating <NUM> the linking drive clutch <NUM> to engage the first clutch part <NUM> and second clutch part <NUM> so that rotation is transferred therebetween and between the first and second drive shafts <NUM>, <NUM>.

Furthermore, in some examples, the clutch controller <NUM> can additionally selectively engage the first clutch part <NUM> and second clutch part <NUM> of the linking drive clutch <NUM> based on further status information of the tugboat <NUM>. For example, in certain pre-defined situations the clutch controller <NUM> receives status information of the tugboat <NUM> such as sudden power drop in one of the prime movers <NUM>, <NUM> or faulty drive clutches <NUM>, <NUM>.

Illustrated in <FIG> is an example of the first sprocket <NUM> connected to the at least one flange <NUM> of the second part 23b of the first drive shaft <NUM>. <FIG> illustrates that the first drive shaft <NUM> already comprises an existing mounting position on the first drive shaft <NUM> between the first and second flanges 28a, 28b. The existing open position has enough space to receive the first sprocket <NUM>. The first sprocket <NUM> can be fastened via bolts <NUM> to the first and second flanges 28a, 28b, as illustrated in <FIG>. Other ways of fastening the first sprocket <NUM> is also possible such as e.g. welding.

Illustrated in <FIG> is another example of the first sprocket <NUM> being connected to the outside surface of the first flange 28a. In order to connect the first sprocket <NUM> to the first flange 28a the first sprocket <NUM> can be in two parts, further seen in <FIG>. In some examples the first sprocket <NUM>, can have a cutout that is big enough for the first sprocket <NUM> to be slid over the first drive shaft <NUM> and into place.

To protect the first and second drive chains <NUM>, <NUM> they may be each enclosed in a chain box <NUM>, illustrated in <FIG> shows a schematic cross-sectional side view of a chain box <NUM> comprising the first drive chain <NUM> and an oiling mechanism <NUM>.

The chain box <NUM> serves at least two purposes. Firstly, the chain box <NUM> shields the crew from the moving first and second drive chains <NUM>, <NUM>. Secondly, the chain box <NUM> protects the first and second drive chains <NUM>, <NUM> from the environment. The chain box <NUM> may extend around the first and second drive chains <NUM>, <NUM> and the first and second sprockets <NUM>, <NUM> on each of the first and second drive shafts <NUM>, <NUM>, as illustrated in <FIG>. The chain box <NUM> can also comprise a sealed bearing (not shown) for the first and second drive shafts <NUM>, <NUM> to pass through.

The chain box <NUM> may also have an oiling mechanism <NUM>. The oiling mechanism <NUM> can be an oil sump <NUM> or reservoir whereby the moving first or second drive chain <NUM>, <NUM> dips into, illustrated in <FIG>. This means that the moving first or second drive chain <NUM>, <NUM> is constantly lubricated during operation. The oil sump <NUM> or reservoir can be situated in the bottom of the chain box <NUM>. Further oiling mechanisms <NUM> can spray oil on to the first sprocket <NUM>, on the first drive shaft <NUM>, or at a first clutch sprocket 49a mounted on the first clutch part <NUM> of the linking clutch <NUM>. <FIG> shows the chain box <NUM> for the first sprocket <NUM> mounted on the first drive shaft <NUM>, the first flexible drive link <NUM> e.g. the first drive chain <NUM> and the first clutch sprocket 49a. An identical chain box <NUM> is provided for the second sprocket <NUM> mounted on the second drive shaft <NUM>, the second flexible drive link <NUM> e.g. the second drive chain <NUM> and a second clutch sprocket 49b mounted on the second clutch part <NUM> of the linking clutch <NUM>. Indeed, in some examples there are a plurality of chains used in the linking drive system <NUM> and each chain comprises a chain box <NUM>. In some examples, alternatively, the spray mechanism <NUM> can spray oil on the first or second drive chain itself <NUM>, <NUM> so that the first or second drive chain <NUM>, <NUM> is constantly lubricated during operation.

The linking drive system <NUM> may also be a kit mountable on the existing vessel propulsion drivetrain systems <NUM>, <NUM>. In an example, the linking drive system <NUM>, in the form of the kit, comprises the first sprocket <NUM>, the second sprocket <NUM>, the linking drive clutch <NUM> and the at least first and second drive chains <NUM>, <NUM>.

In an alternative example of a linking drive system (not shown) for linking together and driving the first and second propulsors <NUM>, <NUM>. A tugboat has the first and second propulsors <NUM>, <NUM>, and the linking drive system comprising a linking drive clutch <NUM> and first and second rigid drive links (not shown).

The alternative linking drive system has most of the same feature and effects as described above except that instead of the first and second flexible drive links <NUM>, <NUM>, any type of first and second rigid drive links can be used. So, the first and second flexible drive links <NUM>, <NUM> are replaced by the first and second rigid drive links.

The placement of the first and second rigid drive links is in a same way as in <FIG> and <FIG> of the linking drive system <NUM>. Thus, the first and second rigid drive links are coupled on the prime mover side of hydraulic pumps for controlling slew of the first and second propulsors <NUM>, <NUM>. Thus, the rotation from one of the first and second drive shafts <NUM>, <NUM> can be transferred to the other drive shaft <NUM>, <NUM> when the clutch <NUM> is engaged, driving the first and second propulsors <NUM>, <NUM> and the slew of the first and second propulsors <NUM>, <NUM>.

Another example will be discussed in reference to <FIG> shows a schematic cross-sectional top view of a tugboat <NUM> having two propulsors <NUM>, <NUM> and a linking drive system <NUM>. The example shown in <FIG> is the same as the examples shown in reference to the previous examples discussed in reference to <FIG>, <FIG>. However, the tugboat <NUM> as shown in <FIG> optionally comprises a firefighting engine <NUM>. The firefighting engine <NUM> can selectively be coupled to the linking drive system <NUM> which will be discussed hereinafter.

The firefighting engine <NUM> is arranged to drive a firefighting system <NUM>. The firefighting (FIFI) system <NUM> comprises at least one pump (not shown) for pumping water out of a nozzle (not shown). The firefighting engine <NUM> is coupled to the linking drive system <NUM> via firefighting engine drive shaft <NUM> and firefighting clutch <NUM>.

In this way, the firefighting engine <NUM> can be used to divert drive to either propulsor <NUM>, <NUM>. For example, this may be required if both the first and second prime movers <NUM>, <NUM> are not operational.

The firefighting clutch <NUM> selectively engages the firefighting engine <NUM> to the linking drive system <NUM>. In normal operation, the firefighting engine <NUM> is isolated the from the linking drive system <NUM> and the firefighting clutch <NUM> is disengaged. In normal operation, the linking drive clutch <NUM> is also disengaged and the first propulsion drivetrain system <NUM> and the second propulsion drivetrain system <NUM> not linked.

Alternatively, if the firefighting clutch <NUM> is disengaged, and one of the first or second prime movers <NUM>, <NUM> is not operational, the other prime mover <NUM>, <NUM> can provide drive to both the first and the second propulsors <NUM>, <NUM> similar to the previous examples discussed in reference to <FIG>, <FIG>.

The clutch controller <NUM> can be of a pure software character and include programming instructions described herein for detection of input conditions and control of output conditions, illustrated in <FIG> and discussed above. The programming instructions can be stored in a memory of the clutch controller <NUM>, not shown. In some examples, the programming instructions correspond to the processes and functions described herein. The clutch controller <NUM> can be executed by a hardware processor. The programming instructions can be implemented in C, C++, JAVA, or any other suitable programming languages. In some examples, some or all of the portions of the clutch controller <NUM> can be implemented in application specific circuitry such as ASICs and FPGAs.

Claim 1:
A linking drive system (<NUM>) coupling together a first drivetrain (<NUM>) and a second drivetrain (<NUM>) of a vessel, the first drivetrain for connecting a first prime mover (<NUM>) and a first propulsor (<NUM>), the first drivetrain comprising a first drive shaft (<NUM>), the second drivetrain for connecting a second prime mover (<NUM>) and a second propulsor (<NUM>), the second drivetrain comprising a second drive shaft (<NUM>); the linking drive system comprising:
- a linking drive clutch (<NUM>), the linking drive clutch comprising at least a first clutch part (<NUM>) and a second clutch part (<NUM>) which are engageable with each other and can transmit rotation therebetween;
- at least one flexible drive link (<NUM>, <NUM>) coupled between the linking drive clutch and the first and / or second drivetrains, wherein the at least one flexible drive link is coupled between the linking drive clutch and the first and / or second drive shafts;
- wherein the linking drive clutch is engageable to allow rotation of one of the first and second drive shafts, generated by a respective one of the first and second prime movers, to be transferred to the other of the first and second drive shafts;
- characterised in that the linking drive system comprises:
- at least a first flexible drive link, the first flexible drive link being coupled between the first drive shaft and the first clutch part of the linking drive clutch; and
- at least a second flexible drive link coupled between the second drive shaft and the second clutch part of the linking drive clutch.