The present invention relates to improvements in marine anchors.

A marine anchor comprises a device including a fluke arranged to engage in a seabed soil to provide a back-reaction for mooring a floating structure via an anchor line attached thereto.

Where a marine anchor includes a permanently attached anchor shackle for connecting to a chain or wire anchor line, connection is often made by means of a D type shackle or a special detachable pear-shaped anchor-connecting link fitted between the anchor shackle and a link of a chain anchor line or a terminating socket of a wire anchor line. The D type shackle accommodates both the large diameter bar of an anchor shackle and the smaller diameter bar of a chain link or a wire line socket whereas the pear-shaped anchor-connecting link is designed to accommodate the two differing bar diameters.

Where the marine anchor is supplied with a detachable anchor shackle intended for threading through a chain end link, connection to a chain anchor line is usually made by means of a three link chain adapter together with a detachable chain connecting link, such as a Kenter link. The three link chain adapter comprises a common link, an enlarged link, and an end link with the end link having an internal aperture length greater than the diameter of an eye of the detachable anchor shackle.

Disadvantages of these arrangements include: low fatigue capability of pear-shaped anchor-connecting links and Kenter links; high cost of the connecting elements; and long delivery times for the connecting elements which often exceed the manufacturing time of the marine anchor. It is an object of the present invention to provide a marine anchor which mitigates these disadvantages.

According to the present invention, a marine anchor includes a plane of symmetry and comprises a fluke member connected to a first clevis member containing a first clevis arranged to open substantially away from said fluke member, characterised in that a second clevis member is pivotably attached to said first clevis member by means of a first pin member located in first bore-holes in said first clevis member and a second bore-hole in said second clevis member, said first bore-holes and said second bore-hole having a common first axis traversing said first clevis and said second clevis member, said second clevis member having a second clevis arranged to open away from said first pin member and including third boreholes having a common second axis traversing said second clevis, said third bore-holes accommodating a second pin member for linking with an anchor line member forming part of an anchor line, said first axis lying in a plane at substantially right angles to said plane of symmetry, said second axis lying substantially in said plane of symmetry, whereby pivoting of said second clevis member relative to said first clevis member and pivoting of said anchor line member about said second pin member and relative to said second clevis member allows said anchor line when taut to swing both in and transverse to said plane of symmetry without being subjected to bending.

Preferably said first clevis member comprises two arm members arranged substantially parallel to each other and spaced apart with one arm member at each side of said plane of symmetry.

Preferably, said first clevis member comprises an end portion of an elongate shank member attached to said fluke member. Preferably, said first clevis member comprises arm members fixedly spaced apart by a spacing member spaced from said first bore-holes.

Preferably, said second clevis member comprises an elongate block containing said second bore-hole at a first end for accommodating said first pin member and a slot, lying in a plane disposed substantially at right angles to said plane of symmetry, at a second end to form said second clevis, said second end containing said third bore-holes for accommodating said second pin member, said third bore-holes being arranged co-axially on said second axis, said second axis being spaced from said first axis.

Preferably, said first axis and said second axis in said second clevis member are spaced apart by a separation distance sufficient to allow said anchor line when taut to swing in a plane at right angles to said plane of symmetry through a swing angle of up to 180 ^° without being subjected to bending due to said anchor line member making contact with said first clevis member.

Preferably, said separation distance is not less than half of the width of said anchor line member plus the maximum extension of said first clevis member extending beyond said first axis away from said fluke member.

Preferably, said spacing member is spaced from said first bore-holes to give said second clevis member sufficient rotational freedom to allow said anchor line when taut to swing in said plane of symmetry through a swing angle of up to 180 ^° without being subjected to bending due to one of said second clevis member making contact with said spacing member and said anchor line member making contact with one of said arm members.

Preferably, said second clevis is adapted to accommodate one of a link of a chain anchor line and a closed socket of a wire anchor line. A particular embodiment of the present invention will now be described by way of example with reference to the accompanying drawings wherein:

Fig. 1 shows an oblique view of a marine anchor according to the present invention attached to an anchor line;

Fig. 2 shows an exploded oblique view of first and second clevis members of the anchor of Fig.1 ;

Fig. 3 shows a side elevation of the second clevis member of Figs.1 and 2.

Referring to Figs.1 to 3, in an embodiment of the present invention, a marine anchor 1 has a plane of symmetry (18A) and includes a fluke 2 and an elongate shank 3 attached to fluke 2 at an aft end 4 of shank 3. Anchor 1 is adapted for direct attachment to a link 5 of a chain anchor line 6 or to a closed socket 7 of a wire anchor line 8. Shank 3 is formed by side plates 9 and transverse plates 10. An end portion 1 1 (Fig.2) of shank 3 distal from fluke 2 forms a clevis member 12 containing first clevis 12A, opening away from fluke 2, comprising two clevis plate arms 13 arranged substantially parallel to each other and fixedly spaced apart by a transverse plate 10A.

An elongate clevis block 14 is located between clevis plate arms 13. First bore-holes 15 present in clevis plate arms 13 and second bore-hole 16 (Figs. 2, 3) present in end 17 of clevis block 14 are of equal diameter and have a common axis 18 arranged orthogonal to plane of symmetry 18A. Each of ends 13A of clevis plate arms 13 are rounded in profile as defined by radius R (Fig.2) centred on axis 18. Close-fitting pin 19 (Figs. 1 , 2) is located in first bore-holes 15 and second bore-hole16 and serves as a pivot about which clevis block 14 is rotatable in plane 18A. First bore-holes 15 in clevis plate arms 13 are spaced from transverse plate 10A sufficiently to allow clevis block 14 freedom to rotate between clevis plate arms 13. End 20 of clevis block 14, distal from end 17, has a slot 21 lying in a plane 22 (Fig. 3) centrally located in clevis block 14 and containing axis 18. Slot 21 divides end 20 of clevis block 14 to form second clevis 14A, opening away from pin 19, having clevis arms 14B. Third bore-holes 23, having a common axis 24 lying in plane of symmetry 18A, are located in clevis arms 14B at end 20 of clevis block 14 to accommodate retaining pin 25 (Fig. 2) for retaining link 5 of chain anchor line 6 or closed socket 7 of wire anchor line 8 in second clevis 14A. Common axis 24 is orthogonal to plane 22 centrally located in clevis block 14 and is spaced by a distance D (Fig.3) from axis 18.

Distance D (Fig. 3) separating axis 18 from axis 24 in clevis block 14 is chosen to be not less than radius R plus half the width of link 5 or closed socket 7 to permit chain anchor line 6 or wire anchor line 8 to swing when taut in a plane at right angles to plane of symmetry 18A through a swing angle (not shown) of up 180 ^° without link 5 or closed socket 7 making contact with clevis plate arms 13.

Transverse plate 10A is spaced from first bore-holes 15 to allow clevis block 14 sufficient freedom to rotate such as to allow chain anchor line 6 or wire anchor line 7 to swing when taut in plane of symmetry 18A through a swing angle (not shown) of up to 180° without being subjected to bending due to clevis block 14 making contact with transverse plate 10A or one of link 5 and closed socket 7 making contact with one of clevis plates 13.

Thus, chain anchor line 6 or wire anchor line 8 when taut can swing freely in two planes at right angles to each other without bending being induced therein by contacts being made as aforesaid.

The inclusion of multiple clevises (12A, 14A) in marine anchor (1 ) provides a sufficient degree of articulation to eliminate need for chain adapters and expensive pear-shaped anchor- connecting links or Kenter connecting links known to have significantly lower resistance to fatigue than an anchor line. It is noteworthy that the arrangement of pin 19 in clevis 12 and clevis block 14 and pin 25 in clevis 14A provides a higher resistance to fatigue than that provided by pear-shaped anchor-connecting links and Kenter connecting links. Further, the inclusion of multiple clevises (12A, 14A) in marine anchor (1) permits overall fabrication to be performed in one facility and so eliminates delays due to long delivery times for particular connecting elements such as shackles.

It will be understood that the particular embodiment described herein may be modified within the scope of the invention. For example, any of transverse plates 10 and 10A may be replaced with rods or bolts and it will be apparent that a second multiple clevis arrangement may be provided in anchor 1 adjacent end 4 of shank 3 to enable a back-up anchor to be connected in tandem thereto via a link of a chain anchor line or a closed socket of a wire anchor line.