Patent Description:
It is a requirement that supply boats or tugboats shall be equipped with an emergency release for releasing the towing hook. If the load on the towing rope becomes too large or the angle between the tugboat and the towing rope becomes incorrect, the tugboat can tilt and be pulled around as it capsizes, with tragic consequences.

For example, a tugboat with a towing rope attached to the tow can be about to turn to get the stern in the direction of travel, and suddenly an acceleration is generated in the tow. Many tugboats do not have stability reserves to withstand the force generated in the tow rope as it tightens across the transverse side. Lack of stability reserves can be due to the towing arrangement which has an effective attachment point of the towing connection approximately amidships and in the centre of the vessel. This makes the tugboat vulnerable to large tilting and capsizing. In such cases, it can be fatal if the emergency release for the towing hook is too far from the maneuvering position. Although the towing connection can be triggered from the current steering position for the boat, this will not remove all hazards.

New Norwegian Regulations require that tugboats and similar vessels shall withstand being pulled transversely through the water at a speed of five knots. The requirement focuses on the attachment point of the towing connection for both longships and transverse ships. The location of the attachment point can thus largely be determined based on the vessel's basic stability.

<CIT> shows a rotatable arm equipped with a hook for receiving a mooring line. A second "heaving line" is used to pull the mooring line through a guide collar and through a groove in the hook and over the hook so that the mooring line is hooked securely onto the hook.

<CIT> shows a tug with a towing hook mounted at the outer end of a towing arm, the inner end of which is mounted on the main deck of the tug in a manner such that the arm can swivel above the main deck from one side to the other side of the tug about an upright axis under the control of a power-operated driving mechanism. The tow line passes through a fairlead and then to the drum of a self-tensioning winch. The drive to the arm augments the steering capability and the characteristics of the winch keep the power required for the drive within controlled limits. The arm is also pivoted about a horizontal axis so that it can swing upwards and downwards and is mounted on a platform, mounted on a carriage which is movable fore and aft on rails on the main deck. These movements of the arm are also controlled by power mechanisms and they adjust the position of the point of action of the tow line in such a way that in whatever direction the tow line extends, even exactly athwartships from the tug, the line of action of the pull in the tow line produces only a small capsizing moment upon the tug.

Documents <CIT>, <CIT> and <CIT> constitute other relevant prior art.

It is an object of the present invention to provide a release system which is to release the towing hook in case of danger of the tugboat capsizing due to excessive tilting and/or trim angle in towing caused by the towing.

The trigger system according to the invention shall, in principle, not be affected by rolling and stamping due to waves. This is achieved by the release system only reacting to the angle between the towing rope/hook and the towboat's longitudinal and transverse vertical axis. The angle between the towing line and the towboats vertical axis for release can be adjusted and can be different for the angles in the horizontal plane so that there can be one angle for trimming, and another for tilting, with a stepless continuous transition.

It is further an object that the release system, on the same basis as mentioned above, releases a towing wire that runs through the towing hook.

In combination, it is thus an object to provide a towing hook that can lock the towing wire to the hook, so it behaves similar regardless if the towing rope is in the hook or the towing wire runs through the hook, such that registration of the hook movements is the same to provide the automatic release.

The towing hook, according to the invention, is designed to be used both with an ordinary tow rope and with wire from a winch and can also be used with a release system described in <CIT> (corresponding to <CIT>) in both configurations. At least some of the sensors can, in this case, be designed as described in said <CIT>.

When used with a towing rope, the release system, according to the invention, automatically releases the towing hook's attachment hook and releases the towing rope at a pre-set danger angle, but when using a towing wire, the release system releases a drum on a winch at a pre-set danger angle.

It is the vertical angle of the towing hook in relation to the vertical axis of the boat that leads to a release when the pre-set danger angle is exceeded. The towing rope loop is attached to the attachment hook when the towing rope is used, so the towing hook will always be in the direction of the towing rope, both horizontally and vertically. For the same to happen when a towing wire from a winch is used, the towing hook, according to the invention, is made so that the towing wire can run through a groove in the middle of the fastening hook.

According to the invention, a release system is provided on a supply boat or tugboat, where the release system comprises a towing hook rotatably mounted and equipped with a fastening hook for receiving a towing rope, in that the fastening hook is equipped to receive an open, through-running groove for receiving a towing wire that runs to a winch. The towing hook comprises one or more sensors which register the vertical and/or horizontal angular direction, and hence the direction, of the towing hook relative to the boat, where said sensors are connected to a control unit which, based on the registered angular directions of the towing hook, is arranged to activate a release mechanism on the towing hook to release the towing wire from the fastening hook or to activate a release mechanism on the winch that lets out the towing wire. The fastening hook of the towing hook comprises two upwardly projecting hook parts for forming the open, through-running groove lying between two said hook parts, where a bolt runs between the two upwardly connecting hook parts of the fastening hook, as the bolt is removable to permit insertion or removal of the towing wire in the through-running track.

The fastening hook of the towing hook is preferably rotatably mounted on a support shaft, where the rotational movement of the support hook is locked or released by the release mechanism.

Furthermore, the fastening hook of the towing hook is preferably rotatably mounted on a support shaft, and the fastening hook comprises a first wire disc in the through-running groove, where the first wire disc is mounted on said support shaft.

The support shaft can be located on the towing hook in an area below the towing rope placement on the towing hook, whereby a lower part of the fastening hook and the first wire disc lies in an opening or recess in the towing hook.

Furthermore, a second wire disc can be mounted on the detachable bolt that runs between the two upwardly extending hook parts of the fastening hook.

A head and a fastening nut of the bolt can, when in use, be detachable recessed in a respective recess on an outside of the two hook parts.

In one embodiment, the towing hook comprises an articulated rotatably turning arm which is mounted on a support shaft equipped with the sensor for registration of the horizontal position of the towing hook and which, in an articulated connection, comprises a rotatable shaft equipped with the sensor for registration of the vertical position of the towing hook.

The towing hook can comprise a first block disc for guiding the towing wire on to the winch, where the block disc, in one embodiment, is mounted on the same support shaft as the towing hook.

In another embodiment, the towing hook can comprise a first block disc for leading the towing wire on to the winch, where the block disc is mounted such that it can flip on a horizontal shaft on the towing hook and follows the movement of the towing hook in the horizontal plane.

The release system can also comprise a second block disc to guide the towing wire to the winch.

The release mechanism on the winch can comprise a locking bolt or ratchet mechanism which can be activated by the control unit based on registered angular directions of the towing hook.

Correspondingly, the release mechanism on the towing hook can comprise a ratchet mechanism which can be activated by the steering unit based on registered angular directions of the towing hook.

Furthermore, the steering unit can be connected to one or more sensors for registration of the tilting angle and trim angle of the boat and where the steering unit releases the winch automatically at dangerous tilting and trimming.

Preferred embodiments of the invention shall, in the following, be discussed in more detail with reference to the accompanying figures, in which:.

Releasers for towing hooks come in many variants, both pneumatic, hydraulic and purely mechanical, such as cord pulls. Common to all is that some form of device is used to release the fastening hook, wheel or fastener itself, which holds the towing rope so that it is released. The releaser can be operated or activated from the wheelhouse or other suitable places on the boat. The releaser is therefore not further explained in the present application, as a releaser for a towing hook is considered known to a person skilled in the art.

In the present description and claims, the entire pivotable unit is called a towing hook, while the hook itself, to which the loop of the towing rope is attached, is called an attachment/fastening hook. A release system according to the invention will comprise a towing hook, discs, winch and releasers, etc. By towing wire is meant a load-bearing wire, cables or the like.

The towing hook <NUM> comprises a swinging arm or a turning arm <NUM> which is mounted on the supply boat or towing boat (not shown) in a support shaft <NUM> which allows rotatable movement of the towing hook in a horizontal plane. Furthermore, the towing hook <NUM> is moved up and down in a vertical plane in that the turning arm <NUM> comprises an articulated connection with a rotatable shaft <NUM>. Alternatively, the support shaft <NUM> can be arranged for said vertical movement. The support shaft <NUM> and possibly the rotatable shaft <NUM> are equipped with sensors <NUM>,<NUM> for registering angular directions, and hence the direction of the towing hook <NUM>, that is the position of the towing hook <NUM> in relation to the boat. The sensors can be, for example, magnetometers or corresponding sensors for the registration of angular directions. The loop of the towing rope <NUM> is attached to the fastening hook <NUM> when the towing rope is used, as shown in <FIG>, so that the towing hook <NUM> will always be in the direction of the towing rope both horizontally and vertically. With the invention the corresponding towing hook <NUM> will stand in the direction of the towing wire <NUM> both horizontally and vertically when a towing wire <NUM> from a winch <NUM> is used, as shown in <FIG> and <FIG>.

On said support shaft <NUM>, a first block disc <NUM> is also arranged, where the block disc lies on the turning arm <NUM> of the towing hook <NUM>. The first block disc <NUM> guides the towing wire <NUM> on to a second block disc <NUM> located at a distance from the towing hook <NUM>, whereupon the towing wire <NUM>, possibly via other block discs or similar, is guided to the winch <NUM>.

The first block disc <NUM> on the towing hook <NUM> can be mounted to follow the towing hook in the horizontal plane but can flip, i.e. be tiltable, about a horizontal shaft such that the towing wire <NUM> can be guided straight into the winch <NUM>, which can then stand some distance vertically over the towing hook <NUM>.

The sensors <NUM>,<NUM> are connected to a control unit <NUM> which, based on registered angular directions of the towing hook <NUM>, can trigger a release mechanism <NUM> on the towing hook <NUM>. The connection to the control unit can be a wired connection with wires <NUM>,<NUM> or be wireless. The control unit <NUM> can also be any logic circuit or programmable unit suitable for the purpose. The release mechanism <NUM> is, in this case, shown as a ratchet mechanism with a lever which can be activated but can, as mentioned, be any known type of release mechanism.

However, the control unit <NUM> can also be connected to sensors <NUM> which are independent of the vertical angle of the towing hook <NUM>, for registration of the tilt angle and the trim angle when the boat is working on tasks such as, for example, anchor handling, where the towing wire <NUM> points downwards into the sea and does not affect the vertical angle of the towing hook <NUM>. By coupling in these sensors <NUM> during such work, the control unit <NUM> of the release system will then be able to ensure that the winch <NUM> is triggered automatically in the event of dangerous tilting and trimming during these operations.

The fastening hook <NUM> of the towing hook <NUM> acts as a normal hook to receive the loop of the towing rope <NUM>. To be able to receive a towing wire <NUM> that runs to the winch <NUM> the fastening hook is equipped with a double hook in the sense that the fastening hook <NUM> comprises upwardly projecting/outwardly projecting hook parts 12a,12b so that an open groove <NUM> or slot between the hook parts is formed, as shown in <FIG>.

In the lower part of the fastening hook <NUM> between the two hook parts 12a,12b, a first wire disc <NUM> is inserted into the groove <NUM> of the fastening hook <NUM>, on the same rotatable bolt <NUM> for the fastening hook <NUM>, but so that the wire disc is hidden in the groove <NUM> and does not come into contact with the towing rope <NUM> when this is used. The rotatable bolt <NUM> is placed so that the lower part of the fastening hook <NUM> and the wire disc <NUM> lie in an opening or recess <NUM> in the outer end of the turning arm <NUM>. The wire disc <NUM> is inserted so that the towing wire <NUM> will slide easily through the fastening hook groove <NUM> without wear on the fastening hook anywhere.

Between the two hook parts 12a,12b, in an area above where the towing wire <NUM> will lie in the groove <NUM>, a detachable barrier in the form of a bolt <NUM> or the like can be mounted, possibly also with a corresponding second wire disc <NUM>. <FIG> shows the fastening hook <NUM> with the second wire disc <NUM> fitted on the bolt <NUM>, while <FIG> shows the fastening hook <NUM> without the second wire disc <NUM>. The bolt <NUM>, or the bolt <NUM> together with the second wire disc <NUM>, thus make up the detachable barrier. The detachable bolt <NUM> is there to be able to be removed and make it possible to remove the towing wire <NUM> when the towing rope <NUM> shall be used and so that the towing hook <NUM> shall follow with the towing wire <NUM> vertically to the direction of the towing wire when used. The bolt <NUM> ends in the form of a head and nuts are preferably mounted countersunk on a respective outside of the fastening bolt <NUM> so that it will not be able to cause wear on a towing rope <NUM> when used.

When towing with towing rope <NUM>, the towing force goes directly to the towing hook <NUM>, while with towing wire <NUM> the towing forces go directly via the block discs <NUM>,<NUM> to the winch drum <NUM> of the winch <NUM>. The winch drum <NUM> comprises a locking bolt or release mechanism corresponding to that of the towing hook, which holds the winch <NUM> until it is released by the automatic release system, or when the winch <NUM> is to be driven manually. This allows the winch <NUM> to hold all the towing forces it can be exposed to without the brake being applied. The winch may be equipped with a water brake to control and regulate the speed when released. The release mechanism on the winch <NUM> is connected to the control unit <NUM> in a wired connection with a wire <NUM> or is wirelessly connected.

The winch <NUM> only needs to have a small, limited traction force and can be used for in and out winding of the towing wire <NUM> when connecting and disconnecting the towing object and can have an automatic brake that works when it shall be driven and the towing safety is automatically disengaged. The winch <NUM> can therefore be small and simple but should have a spooling device and should have its own separate empty zone at the end of the drum where the last <NUM>-<NUM> turns are laid before locking the winch drum <NUM>, so that the towing wire is not damaged by large loads. The towing wire end can be secured to the winch drum only for the permitted towing force so that it is released if the towing wire runs out to the end with too much force during automatic release.

The block discs <NUM>,<NUM> shown, are preferably positioned so that the direction of the towing wire <NUM> in relation to the direction of the block disc is always the same regardless of the direction of the towing hook <NUM> and towards the winch drum <NUM> so that the towing wire, block discs, towing hook or winch are not exposed to undesired wear or influencing on the movement of the towing hook.

Claim 1:
A release system for a supply boat or tugboat, wherein the release system comprises a towing hook (<NUM>) configured to be rotatably mounted and provided with a fastening hook (<NUM>) for receiving a towing rope (<NUM>), where the fastening hook (<NUM>) is equipped with an open, through-running groove (<NUM>) for receiving a towing wire (<NUM>) that runs to a winch (<NUM>), wherein
the towing hook (<NUM>) comprises one or more sensors (<NUM>,<NUM>) which register a vertical and/or horizontal angular direction of the towing hook (<NUM>) relative to the boat,
wherein said sensor(s) (<NUM>,<NUM>) is/are connected to a control unit (<NUM>) which, based on registered angular direction of the towing hook (<NUM>), is arranged to activate a release mechanism (<NUM>) on the towing hook (<NUM>) for release of the towing rope (<NUM>) from the fastening hook (<NUM>) or to activate a release mechanism on the winch (<NUM>) which releases the towing wire (<NUM>), and
the fastening hook (<NUM>) of the towing hook (<NUM>) comprises two upwardly projecting hook parts (12a,12b) for forming the open, through-running grove (<NUM>) lying between said hook parts (12a,12b), where a bolt (<NUM>) runs between the two upwardly projecting hook parts (12a,12b) of the fastening hook (<NUM>), said bolt (<NUM>) being removable to allow insertion or removal of the towing wire (<NUM>) in the through-running groove (<NUM>).