Drag embedment marine anchor

A marine anchor for drag embedment in a submerged soil comprising:

• a fluke;
• a shank attached to said fluke, said shank providing at least one cable attachment point for attachment of an anchor cable, at least a portion of said shank being pivotable about a pivot axis located in said anchor transverse to a fore-and-aft plane of symmetry (M--M) of said anchor, so that said anchor cable attachment point is movable between first and second directions from the centroid of said fluke such that in relation to the forward direction (F) of said fluke measure din said plane of symmetry (M--M) said first direction forms a first forward-opening angle (.alpha.) with said forward direction (F) and said second direction forms a second forward opening angle (.beta.) with said forward direction (F) greater than said first forward opening angle (.alpha.) so that the projected area of said fluke in said second direction is greater than the projected area of said fluke in said first direction whereby a first pulling action on said anchor via said anchor cable at an attachment point located in said first direction permits drag embedment of said anchor by movement substantially in said forward direction (F) in the soil whilst a subsequent pulling action on said embedded anchor in said soil via said anchor cable at an attachment point located in said second direction precludes such movement and;
• remotely operable means to enable selective movement of said anchor cable from said first direction into said second direction;
• said pivot axis being located in any one of two locations which are, (a) in the vicinity of a straight line containing said fluke centroid and said anchor cable attachment point lying in said first direction and (b) aft of said straight line.

A marine anchor for drag embedment in a submerged soil comprising:

• a fluke;
• a shank attached to said fluke, said shank providing at least one cable attachment point for attachment of an anchor cable, at least a portion of said shank being pivotable about a pivot axis located in said anchor transverse to a plane of symmetry (M--M) of said anchor so that said anchor cable attachment point is movable between first and second directions from the centroid of said fluke such that in relation to the forward direction (F) of said fluke measured in a fore-and-aft plane of symmetry (M--M) of said anchor, said first direction forms a first forward-opening angle (.alpha.) with said forward direction (F) and said second direction forms a second forward opening angle (.beta.) with said forward direction (F) greater than said first opening angle (.alpha.), so that the projected area of said fluke in said second direction is greater than the projected area of said fluke in said first direction, whereby a first pulling action on said anchor via said anchor cable at an attachment point located in said first direction permits drag embedment of said anchor by movement substantially in said forward direction (F) in the soil whilst a subsequent pulling action on said embedded anchor in said soil via said anchor cable at an attachment point located in said second direction precludes such movement;
• remotely operable means for enabling selective movement of said anchor cable from said first direction into said second direction;
• first restraint means to restrain said shank such that said anchor cable attachment point lies in said first direction during drag embedment of said anchor;
• and
• first restraint release means for releasing said first restraint means to permit pivoting of said shank to occur to allow said anchor cable attachment point to be moved into said second direction by pulling on the anchor cable following completion of embedment of said anchor;
• said first restraint means being located at the same side of a straight line containing the fluke centroid and aid anchor cable attachment point lying in said first direction as said pivot axis.

A marine anchor for drag embedment in a submerged soil comprising:

• a fluke;
• a shank having an extremity, said extremity of said shank being attached to said fluke;
• and
• means for attaching first and second cables to attachment points on said anchor so as to lie in first and second directions respectively from the fluke centroid, said cable attachment point in the first direction being located close to said forward extremity of said shank means, whereby in relation to the forward direction (F) of said fluke measured in a fore-and-aft plane of symmetry (M--M) of said anchor, said first direction forms a first forward-opening angle (.alpha.) with said forward direction (F) and said second direction forms a second forward-opening angle (.beta.) with said forward direction (F) greater than said first forward-opening angle (.alpha.) so that the projected area of said fluke in said second direction is greater than the projected area of said fluke in said first direction, whereby a first pulling action on said anchor at said attachment point located in said first direction permits drag embedment of said anchor by movement substantially in said forward direction (F) in the soil whilst a subsequent pulling action on said embedded anchor at said attachment point located in said second direction precludes such movement, for both said first and second pulling actions the projection of said shank means orthogonally on to a straight line lying in the forward direction (F) is substantially located aft of a foremost extremity of said fluke.

A method of controlling the load developed by a marine anchor having a shank and fluke during drag embedment when pulled in a mooring bed by an anchor cable attached thereto, said method comprising:

• (a) attaching a control pendant cable to the anchor to enable rotation of the anchor to reduce the angle of inclination of the fluke to the horizontal;
• (b) following said step (a), laying out the anchor on a mooring bed and pulling horizontally on the anchor cable to cause embedment of the anchor into the mooring bed;
• (c) following said step (b), measuring the load developed in the anchor cable as embedment progresses;
• (d) following said step (c), pulling upwards on the control pendant cable when the anchor cable load reaches a designated magnitude and maintaining a force in the control pendant cable sufficient to rotate the moving anchor and reduce the angle of inclination to the horizontal of the anchor fluke and so reduce the holding capacity of the anchor;
• (e) in conjunction with said step (d), noting the effect of the control pendant force on the measured load in the anchor cable;
• and
• (f) in conjunction with step (e), varying the force in the control pendant cable in accordance with the noted effect to control the anchor cable load to a constant designated value as the anchor is dragged to a desired installation location.