The invention relates to a mooring hook for connecting to a mooring line of a ship and/or a floating offshore structure. The mooring hook has a quick release function which can be activated even if mooring hook is under a large load, e.g. a load of 1000 kilonewton. The mooring hook of the invention is typically rated to withstand a predetermined design load of at least 250 kilonewton, e.g. from 250 to 2500 kilonewton. While also being capable of being opened at the design load

Background of the invention

Ships and floating offshore constructions are moored to the shore by means of mooring hooks. Mooring hooks can also be fitted on floating structures or any other suitable location for connection to another maritime object. In general, the ship pays out multiple mooring lines with an eye on each end and this eye is connected to the mooring hook. The hook is equipped with a release system in order to release the mooring line, usually by remote control, in case of departure or in case of emergencies. In order to release, especially in case of an emergency, the mooring hooks should be capable of releasing the mooring line reliably under high load, e.g. of at least 1000 kilonewton, while minimizing mechanical damage and wear to the hook's construction. Mooring hooks may be mounted with a bottom side thereof fixed directly to a quay or maritime object, e.g. using bolts or the like. Most mooring hooks however are equipped with a horizontal connection shaft which is rotatably connected to a stool to allow rotation of the hook around the connection shaft, e.g. when connected to a mooring line which extends at an angle to the horizontal plane. A swivel piece can be mounted between the stool and the hook in order to allow for the hook to rotate around a vertical axis. Often various hooks are combined in a large stool with multiple swivel pieces.

German patent DE 376914 describes a rotatably mounted tow-hook which has a leg at a rear end of the hook, wherein, when the hook is in a closed position, an end of the leg is secured in a forked portion, and when the hook is in a released positon the end of the leg is completely moved out of the forked portion.

From US 5,123,374 a releasable toggle locking mooring hook is known which comprises a releasable hook that is rotatable around a shaft, the hook having an outer hook portion and an inner hook portion on either side of the shaft. The releasable toggle locking mooring hook further comprises a toggle linkage mechanism that is arranged below the shaft and comprises one end attached to the inner portion of the hook, a stop/release mechanism, a self-locking safety latch and a self-release mechanism adapted to provide a secure locking mooring hook and a low friction, low effort releasing means while the mooring hook is under heavy tensile load. The known mooring hook can be used in the mooring of ships, boats and barges to a dock or oil well platform, in which a mooring line, usually under tension, is run from the ship to a mooring means mounted on the dock or platform. When it is desired that the ship leave this moorage, the known mooring means can be actuated manually, mechanically or by a pre-set tensioned self-releasing means to release mooring line and thus, allow the ship to sail.

A drawback of the known mooring hook is that as the inner hook portion of the releasable hook is relatively short, the links of the toggle link mechanism are subjected to high loads. In particular when the hook is in the open or closed position this can result in damage to the links and/or to the shafts connecting the links.

It is an object of the present invention to provide an improved mooring hook in which the above drawback is at least partially overcome.

Summary of the invention

To this end, according to a first aspect, the present invention provides a mooring hook, in particular a quick release mooring hook, for a mooring line, comprising: a support structure supporting a main shaft; a hook body rotatable around the main shaft between an open and a closed position, wherein the hook body has a first leg and a second leg at an angle to the first leg; a first link and a second link each having a first end and an opposite second end, wherein the first link is hingeably connected at its first end to the second leg end by a first hinge shaft and is hingeably connected at its second end to the first end of the second link by a second hinge shaft, and wherein the second link is hingeably connected at its second end to the support structure by a third hinge shaft; wherein, when the hook body is in the closed position, a smallest angle between a first line segment between the axes of rotation of the first and second hinge shaft, and a second line segment between the axes of rotation of the second and third hinge shaft extends between 0 and 20 degrees, preferably between 5 and 9 degrees.

When in the closed position, the first and second link are either parallel to each other or at an acute angle to each other, with the forces exerted by the hook body on the links being directed substantially along the length of each link. When seen in projection onto a plane normal to the main hinge shaft, the first line segment does not form an extension of the second line segment along a straight line when the hook body is in the closed position. When a mooring line exerts a pull on the hook body, the force exerted on the links and on the shafts connected with the links to keep the hook body in the closed position can thus remain relatively small.

When the hook body is in the closed position, and when seen in projection onto a plane normal to the mains shaft, the first segment is preferably arranged between the second segment and the main shaft, though in an alternative embodiment the second segment may be arranged at least partially between first segment and the main shaft. In both cases however the smallest angle is between 0 and 20 degrees.

The configuration of the links allows the hook of the invention to be constructed with its main shaft relatively close to a bottom side of the hook. This is particularly desirable, as in general the shorter a distance of the main shaft to the bottom side of the hook, the smaller the moment that is exerted via the hook on a structure on which supports the hook is supported, e.g. a quay of floating structure, will be. That is, the closer the main shaft is to the structure supporting the hook body, the smaller the chance of the hook body being pulled out of the support structure. Generally, when the hook is in the closed position, a side of the second leg against which the mooring line lies, will face the second hinge shaft and will typically extend upwards. When the hook body is in the open position, the side of the second leg will generally extend in a more horizontal direction to allow the mooring line to be moved out of the hook.

Due to the manner in which forces exerted on the hook body are transferred to the main shaft and the first and second link, the mooring hook of the invention can be of a light weight construction. Assuming both the mooring hook of the invention and the prior art mooring hook of US 5,123,374 are rated for a same pull capacity and are substantially made from a same metal, the mooring hook of the invention, in particular the main shaft, hinge shafts and first and link, thereof, can be constructed using substantially less material, e.g. at least by a factor 2, than in the prior art mooring hook.

In a preferred embodiment both the open and the closed position of the hook body the first hinge shaft hingeably connects the first end of the first link to the second leg of the hook body, the second hinge shaft hingeably connects the second end of the first link to the first end of the second link, and the third hinge shaft hingeably connects the second end of the second link to the support structure. Thus, when then hook is moved from an initial closed position to the open position and vice versa, the links will follow the movement of the hook. In contrast to quick release systems in which the hook is completely uncoupled from any links when in the open position, the present embodiments allows the hook and links to be easily reset to the closed position by exerting a force on the hook. Such a force may for instance be provided on the hook by an elastically deformable buffer block as described below.

In an embodiment, when the hook body is in the closed position, a smallest angle between a further line segment between the axes of rotation of the main shaft and the first hinge shaft, and the first line segment extends between 100 and 130 degrees, preferably between 1 15 and 120 degrees. The further line segment will generally substantially coincide with the direction in which the second leg of the hook body extends. When a mooring line is held by the hook, the mooring line will typically extend from a portion contacting the hook body along a direction substantially parallel to the further line segment. Generally, the more parallel the further line segment is to the direction in which the mooring line extends, the smaller the resulting force will be that is exerted on the main shaft and the support structure.

In an embodiment a, or the, further line segment between the axes of rotation of the main shaft and the first hinge shaft extends substantially horizontally when the hook body is in the closed position. This embodiment is especially suitable for when the hook body is arranged for holding a mooring line which extends substantially horizontally from the hook body.

In an embodiment, when the hook body is in the open position, a smallest angle between the first line segment and the second line segment extends between 160 and 175 degrees. Thus when in the open position, the first, second and third hinge shafts are not aligned on a line, when seen in projection onto a plane normal to these shafts. The impact on the hinge shafts as the hook body moves from the closed position to the open position is thus reduced. The hinge shafts are preferably provided with bearings. A reduction in impact on the hinge shafts will thus also reduce risk of damage to the bearings.

In an embodiment the axes of rotation of main shaft and the third hinge shaft are fixed with respect to the support structure, and the axes of rotation of the first and second hinge shaft are moveable with respect to the support structure. Though the axes of rotation of the main shaft and third hinge shaft are fixed relative to the support structure, the main shaft and third hinge shaft may however be able to rotate around their respective axis of rotation and relative to the support structure.

In an embodiment the mooring hook further comprises a moveable blocking element, such as a rotatable pin, that is supported by the support structure and is moveable between a blocking position and a non-blocking position, wherein the first link comprises a cam portion at its second end, the cam portion being adapted for abutting the moveable blocking element when the hook body is in the closed position and the blocking element is in the blocking position. The moveable blocking element is arranged such that, when in the non-blocking position, it is spaced apart from the cam portion, allowing the cam portion to move beyond the blocking element and in turn allowing the hook body to move from the closed position to the open position. A quick release of the hook body from the closed position to the open position is enabled when the blocking element is moved from the blocking position to the non-blocking position.

In an embodiment the cam portion is arranged for, during movement of the hook body from the open to the closed position, abutting the blocking element to cause the blocking element to move from the non-blocking position to the blocking position. For instance, during movement of the hook body from the open to the closed position, the cam portion may slide over a planar surface of the blocking element, causing rotation of the blocking element to its blocking position.

In an embodiment the first line segment is shorter than the second line segment. This is typically achieved by making the first link shorter than the second link.

In an embodiment the first link comprises two link parts, wherein first hinge shaft and/or the second leg of the hook body is arranged at least partially between said two link parts. The second leg of the hook body may remain free from recesses for accommodating the two link parts, allowing the hook body to be manufactured in a simple manner.

In an embodiment the first link comprises two link parts wherein the first end of the second link is arranged at least partially between the two link parts.

In an embodiment, when seen in projection onto a plane normal to the second hinge shaft, the second link has a curved shape, allowing the second link to deform elastically to temporarily decrease its curvature and increase the length of the second line segment, when the hook body is in the open position. As the hook body snaps from the closed position to the open position, some of the impact on the second and third hinge shaft thus can be compensated for by elastic deformation of the second link from its curved shape to a less curved shape. The curve preferably has a concave side facing the main shaft. More preferably, at least a portion of the concave side facing the main shaft also faces a portion of the second line segment.

In an embodiment the mooring hook further comprises a buffer block that is mounted on the hook body, preferably on a side of the second leg that faces away from the hook point. The buffer block is arranged for absorbing some of the impact when the hook body is moved from the closed position to the open position, by deforming elastically. The buffer block may comprise an elastically deformable material, e.g. an elastomer such as rubber or synthetic rubber. The hook body preferably is provided with a recess in the second leg, for accommodating at least a portion of the buffer block. The buffer block can thus easily be replaced. For instance, the recess may be have a dove tail shape and a portion of the buffer block may have a corresponding shape for fitting in the recess, with another portion of the buffer block projecting out of the recess. Additionally, by arranging the buffer block in this manner it is substantially shielded from contact with the mooring line.

In an embodiment the buffer block is arranged for contacting the first and/or second link when the hook body is in the open position. The buffer block thus moves along with the hook body and generally remains spaced apart from the support structure. By arranging the buffer block in this manner, it is no longer necessary to provide the hook body with a shoulder for abutting a buffer block that is fixed to the front of the support structure. Preferably, buffer block provides an upper limit for the smallest angle between the first line segment and the second line segment when the hook body is in the open position. Preferably the buffer block is arranged for contacting both the first and the second link when the hook body is in the open position, wherein the portions of the first and second link that contact the buffer block are substantially and coplanar and preferably substantially flat. In this manner the impact load is distributed over a wide surface.

In an embodiment a distance between the first hinge shaft and the third hinge shaft is smaller when the hook body is in the closed position than when the hook body is in the open position, preferably at least by a factor 3.

In an embodiment the support structure comprises two plates, one on either side of the hook body, each plate having an outer side facing away from the hook body, wherein the main shaft is arranged completely spaced apart from the outer sides. The main shaft thus does not extend completely through the two plates, though it may extend partially through an inner side of each plate. Consequently, at least near the main shaft, the outer sides of the two plates can thus be substantially smooth, thus minimizing wear of portions of the mooring line which come into contact with the outer sides. Additionally, the risk of a mooring line getting caught on the outside of the mooring hook is reduced as well.

Preferably, the ends of the main shaft are partially inserted into correspondingly shaped recessed portions in the plates, with an edge of the recessed portions abutting the circumferential edge of the corresponding end of the main shaft. A large part of the forces in the connection, which are primarily the result of shear force, can thus be transferred via the circumferential edges at the ends of the main shaft to the support plates. The main shaft typically protrudes into the plates over a depth of about 30-55% of the plate thickness directly around the recesses. E.g. if the plates have a thickness directly around the recesses of 40 mm, then the main shaft may extend about 15 mm into each plate. Each end of the main shaft may be held by fitting faces at the ends of the shaft in the recesses in of the corresponding plates.

In an embodiment the main shaft is connected to the plates via one or more connecting elements, such as bolts, through openings in the plates which extend from an outer side of each plate to its inner side.

In an embodiment the plates comprise upper edges near the point of connection with the main shaft, wherein said upper edges taper upwards towards a centre plane of the support structure which extends normal to the main shaft. When the hook body holds a mooring line, the mooring line is substantially supported by the hook, and may in part be supported by the upwardly tapering edges.

In an embodiment the first leg of the hook body is adapted to extend at an angle of less than 20 degrees to the horizontal when the hook body is in the open position. This allows a substantially horizontally extending mooring line to easily move out of the hook when the hook is mounted substantially horizontally.

In an embodiment the mooring hook further comprises a spring which interconnects the support structure to the first or second link and is adapted for aiding movement of the hook body, and the first and second link over a dead centre position thereof during movement of the hook body from the open position to the closed position. When the hook body is in the open position, the spring may thus assist a person in manually rotating the hook to the closed position. Preferably, the spring is substantially unloaded when the hook body is in the open position.

According to a second aspect, the invention provides a method of returning a hook body in a mooring hook of the invention to a closed position wherein the mooring hook comprises a buffer block that is mounted on the hook body, and wherein the method comprises using elastic energy stored in the buffer block upon opening of the hook body to drive movement of the hook from the open position to the closed position. When the hook body has been moved, due to force exerted thereon, from the closed position to the open position this causes elastic deformation of the buffer block. When the buffer block regains its original shape it exerts sufficient force on the hook body to move the hook body back, preferably completely back, to the closed position. In this manner the mooring hook is quickly available for operation after the hook has been moved to the open position. In case the mooring hook is provided with a blocking element as described above, the blocking element will of course typically be arranged or adapted for allowing the movement of the hook from the open position to the closed position. Short description of drawings

The present invention will be discussed in more detail below, with reference to the attached drawings, in which

Figs. 1 A and 1 B schematically show in side view a prior art mooring hook respectively with a hook body in an open position and a closed position;

Figs. 2A and 2B schematically show in side view a mooring hook according to the invention, respectively with a hook body in an open position and a closed position;

Fig. 3 illustrates forces acting on the mooring hook of Fig. 2A;

Fig. 4 shows an exploded view of the mooring hook of Fig. 2A;

Figs. 5A-5C illustrate moving a blocking element of a mooring hook to allow movement of the hook body from the closed position to an open position;

Fig. 6A and 6B show another embodiment of a mooring hook according to the invention, with a spring for urging the hook body back to the closed position when the hook body is in the open position.

Description of embodiments

Fig. 1A schematically shows a prior art mooring hook 100 having a hook body 130 in a closed position in which it holds a mooring line 1 which extends substantially horizontally from the mooring hook. The hook body 130, which comprises a first leg 131 with a hook point 137, and a second leg 132 that is at an angle to the first leg, is rotatable around a main shaft 150 between the closed position shown in Fig. 1 A and an open position in which the mooring line 1 can move out of the hook body 130 along the direction in which the mooring line extends. The mooring hook 100 is further provided with a support structure 140 comprising two plates on either side of the hook body 130 which support the main shaft 150. Only one of these plates is shown for reasons of clarity.

A first link 1 10 is connected to the hook body by a first hinge shaft 151 and is connected to a second link 120 by a second hinge shaft 152. The second link 120 is connected to the support structure on both sides by a third hinge shaft 153. In the closed condition of the hook body, shafts 151 , 152, 153 are in a straight line to counter the compressive load between the second leg 132 of the hook body 130 and the support structure 140. The first hinge shaft 151 is provided at an end of the second leg 132, which end lies on one side of the main shaft 150 and the hook point 137 lies on an opposite side of the main shaft 150. Below the second hinge shaft 152 a support block 141 is fixed to the support structure and abuts the first and second link. Further, below the hook body 130 a buffer block 147, comprising an elastomer such as rubber, is fitted in a recess of the support structure 140, for stopping the hook body when opened under load, see also Fig 1 B. The support structure 140 can be connected at its bottom side to a quay / or ship structure, or can be connected via connection shaft 142 to a swivel or other structure (not shown for reasons of clarity). The mooring line 1 has an eye, which, after having been slid over the upward hook point 131 of the hook body 130, rests on an upper edge of the support structure 140 and abuts the hook body. The hook body can be moved from the closed position shown in Fig. 1 A to the open position shown in Fig. 1 B, by moving the second link shaft 152 upward from the support block 141 by means of a separate actuation mechanism (not shown), so that the hinge shafts 151 ,152,153 are no longer arranged in a straight line and cannot withstand the compressive load without moving. Due to the pull on the hook body 130 by the mooring line 1 , the hook body then rotates counter clockwise until stopped by the buffer block 147, which is shown in Fig. 1 B to be elastically compressed. The first link 1 10 and second link 120 will then rotate upward until they are again arranged in a straight line, and the mooring line slides over the hook body point 130 and out of the mooring hook 100. Once the mooring line 1 no longer exerts a pull on the hook body 130, the buffer block 147 expands back to its undeformed rest configuration, causing the hook body to rotate back towards the closed position.

Figure 2A schematically shows a mooring hook 200 according to the invention. The mooring hook 200 is provided with a hook body 230, a support plate structure 240, a first link 210 and a second link 220. The support structure 240 comprises two side plates, only one of which is shown in Figs. 2A and 2B to allow the interior of the mooring hook 200 to be seen more clearly. When the mooring hook 200 is in use, the support structure 240 may be connected at its bottom side to a quay / ship structure, or may be connected via a connection shaft 242 to a swivel or other structure.

The hook body 230 is rotatable around main shaft 250 between the closed position shown in Fig. 2A and the open position shown in Fig. 2B. The main shaft 250 is connected on either side of the hook body 230 to support plates of support structure 240. The first link 210 is connected to the hook body by a first hinge shaft 251 and to the second link 220 by a second hinge shaft 252. A second link 220 is connected to the support plate structure 240 on both sides by a third hinge shaft 253, and the axes of rotation of the main shaft and the first, second and third hinge shafts extend parallel to each other. A first line segment 11 extends along the first link 210 between the axes of rotation of the first and second hinge shafts 251 ,252, and a second line segment I2 extends along the second link 220 between the axes of rotation of the second and third hinge shafts 252,253.

The second link 220 has a curved shape which is concave towards the main shaft 250. When, during opening of the mooring hook a high load is applied on the second and third hinge shaft 252, 253 in the direction of the second line segment I2, the second link 220 can elastically deform to a less curved shape and absorb some of load. The elastic deformation may temporarily absorb some of the sudden loads on the second and third hinge shaft when the hook body is in the open position, in this manner reducing risk of damage to the second and third hinge shafts.

In the closed position of the hook body 230, as shown in Fig. 2A, and when seen in projection onto a plane normal to the axis of rotation of the main shaft 250, a smallest angle a1 between the first and second line segments extends at about 15 degrees. A smallest angle B1 between the first line segment 11 and a line segment m2 which extends between the axis of rotation of the first hinge shaft 210 and the axis of rotation of the main shaft 250, is about 1 15 degrees.

A rotatable locking pin 260 is provided between both plates of the support plate structure 240, the pin having a partially cylindrical outer surface 261 at a substantially constant distance to the pin’s axis of rotation, and further having a substantially planar surface 262 which lies closer to the pin’s axis of rotation than does the cylindrical outer surface. The pin is arranged for abutting a cam portion 215 of the first link 210 with its cylindrical outer circular surface 261 in such a manner that the pin blocks the cam portion 215 from rotating, in this manner blocking any movement between the first and second link which would increase the first angle a1 . The pin may be rotated, e.g. using a lever or actuator connected to the pin, in such a manner that its cylindrical outer surface 261 is turned away from the cam portion 215, allowing the cam portion 215 to slide past the planar surface 262 and also allowing relative movement between the first and second link so that the hook body 230 can be rotated to the open position.

The hook body comprises the first leg 231 with a hook point 237 around which an eye of the mooring line 1 can be slid, and a second leg 232 that extends at an angle to the first leg. The first link 210 is connected by the first hinge shaft 251 to an end of the second leg 232. A line segment ml extends substantially from the hook point 237 to the axis of rotation of the main hinge shaft 250, substantially parallel to the inner shape of the hook point. In the closed position shown, line segment ml is substantially parallel to line segment I2. An acute angle g between the line segments ml and m2 is about 60 degrees.

On a side of the second leg which faces away from the hook point 237, the second leg is provided with an accommodation space 233 which holds a buffer block 234 so that the buffer block is arranged for rotating in conjunction with the hook body 230. The buffer block is spaced apart from the support structure 240.

Fig. 2B shows the mooring hook 200 of Fig. 2A, in which the hook body 230 has been moved to an open position. By rotating the locking pin 260, the cam 215 was allowed to move past the planar surface 262 of the pin 260, in turn allowing the second link 220 to rotate clock wise and hook body 230 to rotate counter clockwise due to a pull exerted on the hook body 230 by the mooring line 1. This rotation continues until the ends of second link 220 abut the buffer block 234 of the hook body 230, causing elastic deformation of the buffer block. In this position the hook body is in the open position, in which the smallest angle a2 between the first and second line segments about 165 degrees, and the largest angle b2 between the first line segment 11 and line segment m2 is about 310 degrees. In this open position the mooring line can easily slide out of the mooring hook 200.

Once the mooring line 1 no longer exerts a pull on the hook body, the hook body can rotate back into locked position due to the force exerted on the hook body by the buffer block 234 when the elastically deformed buffer block reverts back to its original shape. Typically, in order for the buffer block to be able to drive movement of the hook body back to the closed position, the load under which the hook was opened should at least be 20% of the hook’s design load.

Figure 3 schematically illustrates various forces acting on the various components in the mooring hook 200 when the hook body 230 is in the closed position and the pin 260 blocks relative movement between the first and second links 210,220 towards the open position. Here the pin is shown to be connected to a lever 264 which can be used to rotate the pin 260 between a blocking position in which the pin abuts the cam portion 215, as shown, and a non-blocking position in which the cam portion can move past the pin 260. The mooring line 1 acts on the hook body with a substantially horizontally directed force F at a first moment arm distance d1 . This moment is transformed via the main shaft 250 into a load force F _si at the first hinge shaft 251 at a second moment arm distance d2. The first link 210 connects this load force Fsi via the second hinge shaft 252 to the second link 220. At the second hinge shafts 252, the load force Fsi can be considered to be split up into a force component Fu parallel to first line segment 11 and a force component FL2 parallel to the second line segment I2 (see Fig. 2A). The second link 220 connects the load via the third hinge shaft 253 to the support plate structure (not shown). The combination of force Fu and FL2 is substantially equal to the resultant force F _P exerted by the cam portion 215 on the locking pin 260. The sum of force F and force Fsi substantially equals the resultant force FM that is exerted on the main shaft 250.

In Fig. 3 the horizontally directed force F exerted on the hook body 230 by the mooring line 1 extends at a smallest angle f of about 5 degrees to line segment m2. The resultant force FM that is exerted on the main shaft 250 is at a smallest angle Q of about 15 degrees to the direction of force F. In the closed position of the hook body 230 shown, segment ml extends substantially parallel to segment 11. In any case, segment 11 has a length that is smaller than the length of segment I2. In the example shown, in which the mooring hook 200 has a predetermined design load of 1000 kilonewton, segment 11 has a length of about 26 cm, whereas segment I2 has a length of about 39 cm. Segment m2 has a length of about 33 cm, and the lever 263 that is connected to the pin 260 has a length of about 60 cm.

Fig. 4 schematically shows an exploded view of the mooring hook 200. The support structure 240 comprises two plates 240a, 240b between which the main shaft 250 is held. The main shaft 250 does not extend completely through the plates 240a, 240b, but is placed with its ends against recessed portions 243b on the inner sides 241 a, 241 b of the plates, in such a manner that circumferential surfaces of the ends lie against edges of the recessed portions. Shear forces on the main shaft can thus be transferred via the circumferential surfaces at the ends of the main shaft to the plates. In other words, the main shaft is provided at its end with fitting faces which fit in the recesses.

The main shaft does not project beyond the outer sides 242a, 242b of the plates 240a, 240b, allowing the outer sides to be substantially smooth thus reducing the risk the outer sides causing wear of the mooring line. Bolts which extend from recesses in the outer side into the main shaft ensure the main shaft is held in place relative to the support structure. The third hinge shaft 253 is also arranged completely between the inner sides 241 a, 241 b of the plates, and can be fastened to the support structure using bolts as well.

The first link, which is referred to in Figs. 2A, 2B and 3 with reference numeral 210, comprises two parallel parts 210a,210b which are attached on either side of the hook body 230 to the first hinge shaft 251 . The second link 220 moves partially between these two parts 210a, 210b when the hook body 230 moves from the open position to the closed position and vice versa. The second link 220 has a somewhat curved shape, allowing the second link to deform elastically along the direction of line segment I2 when the hook body is in the open position. The elastic deformation of the second link reduces the impact on the first and second hinge shafts, and thus helps to prevent deformation of these hinge shafts and bearings in which these hinge shafts are arranged.

The parts 210a, 21 Ob of the first link each comprise a cam section 215a, 215b for abutting the pin 260. When the cam sections abut cylindrical surfaces of the pin, movement of the first link parts 210a, 210b from beyond the pin is blocked. When the lever 264 is pulled until the planar portions 262 of the pin face the cam sections 215a, 215b and are spaced apart therefrom, the pin no longer blocks the cam sections and the cam sections can slide past pin, allowing the hook body to move to the open position.

The design of the hook 200 allows the outer surface of the main shaft 250 to lie relatively close, i.e. well within one fourth of the diameter of the main shaft, to upwardly tapering edges

244a, 244b of the plates 240a, 240b at a location near the main shaft 250, as can also be seen in Figs. 2A and 2B. The total height of the mooring hook 200, and in particular the total distance of the portion of the hook body which holds the mooring line to a bottom side of the mooring hook, is thus kept small.

Figs. 5A-5B illustrate how the pin 260 can be rotated using a lever, though any other kind of actuator for rotating the lever could be used instead. The lever is biased, e.g. by means of a spring or the like, to the position shown in Fig. 5A. In Fig. 5A the pin 260 is in a blocking position in which its cylindrical outer surface 261 abuts the cam portion 215 of the first link 210, in this manner blocking the first link from moving past the pin. In Fig. 5B the lever has been pulled, e.g. using a powered actuator or via a rope attached to the lever, so that the cylindrical outer surface no longer abuts the cam portion 215 and the first link can move past the pin 260.

Fig. 5C illustrates that, when hook body 230 rotates back to the closed position and the cam 215 moves counter clockwise in the opposite direction, the sloping side of the cam 215 presses on planar surface 262 of the locking pin 260. This will cause the pin and the lever arm 264 connected thereto to rotate a few degrees clockwise, enabling cam portion 215 to pass. Once the cam portion has returned to the position as in Fig 5A, the bias on the lever will cause the locking pin 260 and lever arm 264 rotate back to their original position and lock the cam portion 215 behind the locking cylindrical surface portion of the pin 260.

Figs 6A and 6B show a portion of a mooring hook 600 according to a further embodiment, respectively with the hook body 630 in an open position and a closed position. The mooring hook

600 is provided with a tension spring 670 which interconnects second link 620 to the support structure 640. Except for the spring, the mooring hook 600 has a similar construction as the mooring hook of Figs. 2A and 2B, and comprises a first link 610, main shaft 650, first, second and third hinge shaft 651 ,652,653, pin 660 and so on. If the pin is moved to the non-blocking position while the mooring line exerts a force on the hook body that is 20% or less of the hook's design load, then the elastic deformation of the buffer block and subsequent return of the buffer block to its undeformed state, may not be sufficient to return the hook body to the closed position. In that case a person may have to manually push the hook body back to the closed position, during which the spring will assist in moving the hook body and first and second link over a dead centre position thereof. The spring 670 is adapted to assist in returning the hook body to the closed position following a release with marginal load (e.g. less than 20% of the mooring hook’s design load) in which the elastic deformation of the buffer block is insufficient to return the hook body to the closed position. The spring is substantially unloaded when the hook body is in the completely open position.

The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims. In particular, though in the figures illustrate the mooring hook of invention has been shown in combination with a mooring line with a substantially completely horizontally directed mooring line load, it will be appreciated that the mooring hook can also be used for mooring lines which extends at an angle to the horizontal.