GB2520094A

GB2520094A - Pole Engagement device for marine vessels

Info

Publication number: GB2520094A
Application number: GB1403224.7A
Authority: GB
Inventors: Stephen James Phillips
Original assignee: SOUTH BOATS IOW Ltd; Alicat Workboats Ltd
Current assignee: SOUTH BOATS IOW Ltd; Alicat Workboats Ltd
Priority date: 2013-09-17
Filing date: 2014-02-24
Publication date: 2015-05-13
Also published as: GB201316490D0; GB201403224D0

Abstract

A pole engagement device 1 for a marine vessel comprises a tapered recess 2 for engaging with a docking pole Z of a marine structure such as a wind turbine. The recess has an opening 2A for receiving the docking pole and a pair of opposed, converging faces 3A and 3B that in use contact either side of the docking pole when it is received within the recess. An inner end of the recess has a width less than that of the opening. The device is arranged such that in use the contact force between the docking pole and the pair of opposed faces is greater than a thrust force urging the docking pole into the recess, allowing for enhanced vessel stability during docking and crew transfer.

Description

Pole Engagement Device for Marine Vessels The present invention relates to a pole engagement device for marine vessels.

Background

Wind farms make use of wind turbines (sometimes referred to as windmills) to convert wind energy into electricity. In offshore wind farms it is often desirable to make repairs to wind turbines. Most wind turbines have a tower extending from the sea bed with one or more vertical mooring poles adjacent a ladder extending up the tower. In order to make repairs, a vessel transporting a technician needs to dock onto the or each pole so that the technician can transfer to the ladder and then climb up the tower.

A common practice is to drive a vessel's bow onto a pole whilst using the vessel's engine thrust to hold it into position whilst a technician transfers to a tower ladder, but the bow can fall way from the pole, especially in a swell, as the vessel heaves, pitches, rolls and yaws. It is known to provide a hydraulic clamp on the bow of a vessel to secure the vessel onto the pole which can accommodate both pitch, roll and yaw of a vessel, but these are expensive and heavy to install on a vessel, and the complicated mechanics are prone to corrosion and failure with sea water breaking over them in rough weather.

The invention seeks to provide a simple solution to supporting a vessels bow against a wind turbine tower pole or poles.

Summary of Invention

The invention provides a pole engagement device as defined in the appended independent claims, to which reference should now be made. Preferred or advantageous features of the invention are set out in dependent sub-claims.

A pole engagement device defined by a portion of the bow of a vessel, or for fitment to the bow of a vessel, may comprise a tapered recess to receive a pole between opposing faces of the recess and to create a pair of contact points either side of the pole, whereby a force created by the vessel moving forward towards, or urged towards, the pole causes a greater force at the contact points on the pole.

A pole engagement device defined by, or for fitment to, the bow of a vessel, may comprise a tapered recess having an opening to receive a pole, opposing faces of the tapered recess contacting either side of the pole when the pole is received by the tapered recess, whereby a first force created by the vessel being urged towards the pole causes a second force at contact points between the opposing faces of the tapered recess and the pole, the second force being greater than the first force.

A pole engagement device may comprise a recess for engaging with a docking pole of a marine structure, the recess having a first end defining an opening for receiving the docking pole, the opening preferably having a width greater than the diameter of the docking pole, a second end having a width less than the diameter of the docking pole, and a pair of opposing faces extending between the first end and the second end, in which the opposing faces converge within the recess such that a contact force between the docking pole and the pair of opposing faces is greater than a thrust force urging the docking pole into the recess. If the opening has a width equal to or less than the width of the docking pole, the opening must be of sufficient width to enable the docking pole to engage with the opposing faces of the recess.

A pole engagement device according to any aspect of the invention produces a force multiplication effect to increase the frictional force available to restrain the bow of a vessel against a docking pole over that normally resulting from the propulsive thrust of a vessel. The propulsive thrust moves the vessel towards the pole or urges the vessel against the pole.

The pole engagement device may be for use in docking a vessel with any marine structure having a docking or mooring pole. Typically, the marine structure will be a wind turbine. The marine structure may be a structure possessing a docking pole for allowing crew transfer, such as a lighthouse, or a rig, or a larger vessel.

A docking pole of a wind turbine typically has a diameter of about 330 mm. A recess of a pole engagement device for engagement with a typical pole will, therefore, have an opening with a width of between 300 mm and 400 mm to allow engagement of the pole with opposing faces of the device within the recess.

Figure 3 illustrates a conventional docking arrangement between a vessel 30 and a docking or mooring pole 40 of a wind turbine. A rubber fender 50 on the bow of the vessel 30 is pushed up against the docking pole 40 and makes contact with the pole at a point 45. Thrust (F) provided by the vessel's propulsors results in a frictional force between the fender and the docking pole, which restrains the bow of the boat sufficiently for crew transfer. The frictional force available to prevent the fender sliding off the docking pole is both a function of the force by which it is being pushed onto the docking pole (thrust force -F) and the coefficient of friction of the fender material against the docking pole. There are also other considerations, such as whether the interface is wet, whether the materials are strong enough to support the theoretical friction force and whether deformation of the materials changes the local angle of contact.

For a rubber fender on a steel pole, the maximum coefficient of friction is approximately 0.7.

Thus for a thrust force of F, the maximum frictional force available from a conventional fender is approximately 0.7 x F as per Figure 3.

In the present invention a docking pole engages with opposing faces within a tapered or V-shaped recess. This allows the resultant normal force (FN) at the points of contact to be considerably greater than the thrust force produced by the propulsion system. It can be seen in the simplistic force diagrammatic in Figure 4 how the resultant normal force (FN) is related to the thrust force (F).

Figure 4 schematically illustrates a docking pole engaged with opposing faces 11, 12 of a tapered recess 10. Each opposing face is tapered by 30 degrees. For a taper angle (ci) of 30 degrees (when the total angle (2a) formed by convergence of the opposing faces is 60 degrees), the resultant normal force equates to the thrust force divided by the sine of 30 degrees making the resultant force at the point of contact twice the thrust force. This can be shown by the equation; Resultant Normal Force = Thrust (F) / Sin 30 = F /0.5 = 2 x F lithe taper angle (a) is decreased to 20 degrees then the resultant normal force is about three times the thrust force, and for a taper angle of 15 degrees, about four times the thrust force.

Thus, the use of a tapered recess acts to provide a contact force at the point of engagement between a docking pole and a vessel, which is a multiple of the thrust force urging the vessel into contact with the pole.

A recess has a first end defining an opening and a second end opposite the opening. Side walls or faces extend between the first end and the second end. Such side walls may be termed opposing faces. A recess axis may be defined extending between a central point of the first end, or opening and a central point of the second end. The angle between the direction of the opposing faces and the direction of the recess axis may be termed the taper angle.

Preferably, the taper angle is between 10 and 30 degrees, for example about 20 degrees, or about 25 degrees. Thus, preferably the total angle formed by convergence of the opposing faces is between 20 and 60 degrees, for example about 40 degrees, or about 50 degrees.

As used herein the term tapered recess indicates a recess having opposing side faces or walls that converge within the recess. The opposing faces may be planar. The opposing faces may be curved in one or more planes. A tapered recess may be a V-shaped recess or a wedge shaped recess. Engagement between the tapered recess and a docking pole results in two-point contact on the docking pole.

The dimension of the pole engagement device that extends along the longitudinal axis of the pole with which the device engages may be termed the depth of the device. Typically this is a vertical dimension as a docking pole will usually be arranged vertically. The depth of a pole engagement device is preferably between 200 mm and 1000 mm, for example between 400 mm and 800 mm. Preferably the depth is between 500 and 700 mm, for example about 600 mm.

For preferred applications the thrust force of a vessel utilising the pole engagement device will be between 1 ton and 20 tons depending on the size of the boat and the power of its engines.

That is, the thrust force urging the device against the pole is preferably between 1 ton and 20 tons. The contact force developed between the pole and the device may be multiples of the thrust force. Stress developed in the materials in contact (materials of the pole and the opposing faces of the recess) depends on the contact force and the contact area. Where a high contact force is developed the contact area is preferably sufficiently high to prevent the stress in the materials from exceeding a failure stress of that material. Where the opposing faces comprise a rubber material, the contact area between the pole engagement device and a pole may preferably be within the range between 1000 mm2 and 50,000 mm2.

The recess extends for a suitable distance along the fore-aft axis of the vessel. Preferably the recess extends between 200 mm and 400 mm, for example between 260 mm and 360 mm.

Preferably the opposing faces are curved in a vertical and/or horizontal plane.

Preferably the opposing faces are formed from a high friction material. The material may be of resilient material. The material may be a rubber or synthetic rubber. The material may be selected from the list consisting of natural rubber, synthetic rubber, butyl rubber, hypalon, neoprene, nitrile rubber, poly-acrylate, fluoro-elastomer and silicone rubber.

Preferably the pole engagement device further includes a joint means to secure the engagement device to the bow of a vessel, said joint means allowing the pole engagement device to pitch, roll or yaw relative to the vessel.

Preferably the pole engagement device further includes a shock absorbing means to absorb shock when the pole engagement device engages a pole and/or experiences a wave slam.

Preferably a sensor is provided to indicate the forces at the contact point. The sensor may sense the vertical force between pole engagement device and the pole as the vessel moves up and down in swell.

Preferably a release device is provided to bias the pole out of the tapered recess. The release device may include a roller adjacent the base of the recess drivable towards the open end of the recess.

Preferably a gangplank is provided adjacent the recess to allow a person to reach a mooring pole or a point adjacent the pole such as a ladder, said gangplank having one end pivoted to the bow of a vessel and a free end biased towards the pole.

An embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1A shows a perspective view of the bow of a vessel with a pole engagement device, Figure 1 B shows a perspective view of the bow of a vessel with the pole engagement device on a mooring pole, Figure 2A shows the pole engagement device of Figure 1 engaging a single pole on a tower, and Figure 2B shows the pole engagement device of Figure 1 engaging a double pole on a tower.

Referring to Figures 1A and lB there is shown a pole engagement device 1 for fitment to the bow X of a marine vessel such as a catamaran.

Pole engagement device 1 comprises a tapered recess 2 having a wider open end 2A and a narrower closed end 2B. Recess 2 has a pair of opposing faces 3A,3B which are curved in the vertical plane and linear in the horizontal plane (although they could be curved in the horizontal plane). Opposing faces SA,3B are formed from high friction resilient material such as rubber or synthetic rubber. Recess 2 is adapted to receive a vertical mooring pole Z on a wind turbine tower between opposing faces of the recess and to create a pair of contact points A, B either side of the pole, whereby a force created by the vessel moving forward towards the pole causes a greater force at the contact points on the pole.

A release device in the form of roller 4 driven by a ram 5 is provided which can be driven towards or away from the recess open end 2A.

A gangplank 6 is provided adjacent the recess to allow a person to reach a second mooring pole Y or a point adjacent the pole such as a ladder. Gangplank 6 has one end GA pivoted to the bow of a vessel and a free end 6B biased towards the pole by a spring 7.

In use, the vessel can dock on the pole by moving up to the pole slowly and engaging the pole in the recess 2. The vessel can use its engines to apply forward thrust to the vessel so pushing the pole into the tapered recess. The opposing faces 3A,3B will grip the pole at the contact pointA,B so preventing the bow of the vessel moving up and down in any swell.

Because the opposing faces are angled a few degrees (e.g. up to 30 degrees) either side of the fore and aft line of the vessel, the force at the contact points A,B will be greater than the force applied by the vessel's engines in a forward direction. Thus if the vessel's engines apply a forward force of 5 tons towards the pole, the force at the contact points A,B may be two or three times this value.

As the vessel engages the pole, the roller can abut the pole to accommodate up and down movement of the bow of the vessel until the pole is gripped by the contact points. If it is necessary to release the grip of the contact points, roller 4 can driven by a ram 5 towards the recess open end 2A to push to pole out of the recess.

As shown in Figure 1 B, the gang plank free end GB can abut a second pole Y, and be maintained against the pole Y by spring 7 as the vessel yaws about pole Z. A technician can use the gangplank to climb onto a tower. Gangplank free end could alternatively abut against a point on a tower such as a ladder instead of pole Y. As shown in Figure 2A a single recess 2 may be provided on the bow of a boat X to engage with a single pole Z on a tower. Alternatively a pair of recesses 2 could be provided on a bow to engage with a pair of poles Y,Z on a tower as shown in Figure 2B.

The invention may take a form different to that specifically described above. For example the pole engagement device may further include a joint means to secure the device to the bow of a vessel, said joint means allowing the pole engagement device to pitch, roll or yaw relative to the vessel. The pole engagement device may further include a shock absorbing means to absorb shock when the pole engagement device engages a pole. A sensor may be provided to indicate the forces at the contact point. The sensor may sense the vertical force between pole engagement device and the pole as the vessel moves up and down in swell.

Further modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

Claims

CLAIMS1. A pole engagement device defined by, or for fitment to, the bow of a vessel, said pole engagement device comprising a tapered recess having an opening to receive a pole, opposing faces of the tapered recess contacting either side of the pole when the pole is received by the recess, whereby a first force created by the vessel being urged towards the pole causes a second force at contact points between the opposing faces of the tapered recess and the pole, the second force being greater than the first force.
2. A pole engagement device comprising a recess for engaging with a docking pole of a marine structure, the recess having a first end defining an opening for receiving the docking pole, the opening preferably having a width greater than the diameter of the docking pole, a second end having a width less than the diameter of the docking pole, and a pair of opposing faces extending between the first end and the second end, in which the opposing faces converge within the recess such that a contact force between the docking pole and the pair of opposing faces is greater than a thrust force urging the docking pole into the recess.
3. A device according to claim 1 or 2, wherein the opposing faces are curved in a vertical and/or horizontal plane.
4. A device according to claim 1, 2, or 3, wherein the opposing faces are formed from a high friction material.
5. A device according to claim 4, wherein the material is of resilient material.
6. A device according to claim 4 or 5, wherein the material is a rubber or synthetic rubber.
7. A device according to any preceding claim, wherein the pole engagement device further includes a joint means to secure the engagement device to the bow of a vessel, said joint means allowing the pole engagement device to pitch, roll or yaw relative to the vessel.
S. A device according to any preceding claim, wherein the pole engagement device further includes a shock absorbing means to absorb shock when the pole engagement device engages a pole and/or experiences a wave slam.
9. A device according to any preceding claim, wherein a sensor is provided to indicate the forces at the contact point.
10. A device according to claim 9, wherein the sensor senses the vertical force between pole engagement device and the pole as the vessel moves up and down in swell.
11. A device according to any preceding claim, wherein a release device is provided to bias the pole out of the tapered recess.
12. A device according to claim 11, wherein the release device includes a roller adjacent the base of the recess drivable towards the open end of the recess.
13. A device according to any preceding claim, wherein a gangplank is provided adjacent the recess to allow a person to reach a mooring pole or a point adjacent the pole such as a ladder, said gangplank having one end pivoted to the bow of a vessel and a free end biased towards the pole.
14. A pole engagement device for fitment to the bow of a vessel substantially as hereinbefore described with reference to and as shown in the accompanying drawings.