Ships – Anchor – With dislodgement means
Patent
1998-01-20
1999-04-06
Sotelo, Jesus D.
Ships
Anchor
With dislodgement means
114304, B63B 2124
Patent
active
058904514
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to drag embedment marine anchors and to a type of anchor adapted for loading normal to the anchor fluke after installation.
An anchor of the said type is disclosed in the present inventor's application PCT/GB92/02210 entitled "Drag Embedment Marine Anchor" and comprises a fluke and a shank means attached to the fluke and arranged to provide at least one attachment point for attachment of an anchor cable, said shank means being adapted such that the anchor provides two directions from the centroid of the fluke to said attachment point whereby, in relation to the forward direction of the fluke measured in a fore-and-aft plane of symmetry of the anchor, a first direction forms a first forward-opening angle with said forward direction and a second direction forms a second forward-opening angle with said forward direction greater than said first forward-opening angle whereby a first pulling action on the anchor at an attachment point located in said first direction permits drag embedment of the anchor by movement substantially in said forward direction in the soil whilst a subsequent pulling action on the embedded anchor at an attachment point in said second direction substantially transverse to said forward direction precludes such movement, the projected area of the fluke in said second direction being greater than the projected area of the fluke in said first direction so that a greater resistance to movement of the anchor is present for said subsequent pulling action than for said first pulling action. Since an anchor of this type may be described as a Drag Embedment Normal Load Anchor, the acronym Denla will be used hereinafter to denote an anchor of the type described hereinbefore.
Hitherto a Denla has been installed in shallow water by means of two lines: the anchor line and an auxiliary pendant line attached to the rear of the fluke to control the heading of the Denla and remotely activate its triggering mechanism. Recovery after use has been effected by heaving up on the pendant line to rotate the Denla in the soil and then pull it to the sea bed surface against low resistance loads engendered by edge-wise rearwards movement of the fluke. However, in deep water installations necessitating long lines, it is possible for the two lines to become twisted together whereby control is lost of the heading of the Denla thus preventing successful deployment.
It is an object of the present invention to provide anchoring apparatus capable of being installed and subsequently easily recovered by means of an anchor line without recourse to an auxiliary pendant line.
Another object of the present invention is to provide a method of installing and recovering said anchoring apparatus.
According to a first aspect of the present invention, an anchoring apparatus for drag embedment in a submerged soil by means of an anchor cable comprises an anchor and a drogue line attached to a rear portion thereof which hangs vertically as the anchor is lowered proximal to the sea bed surface while suspended by the anchor cable whereby, when the apparatus is moved horizontally with a portion of the drogue line dragging in contact with the sea bed surface, a horizontal motional resistance force is produced by the drogue line which is equal and opposite to the horizontal component of force in the anchor cable and in aligning therewith acts to constrain the suspended anchor to point only in the direction of dragging motion.
Preferably said drogue line is attached to an aftermost point on the anchor.
Preferably an end of said drogue line remote from said anchor includes a resistive element capable of providing considerable motional resistance when dragged in contact with the sea bed surface.
Preferably said resistive element comprises a length of heavy chain.
Preferably the length of said drogue line is between 1.5 and 4 times the length of the fluke of the anchor.
According to a second aspect of the present invention, an anchoring apparatus for drag embedment in a submerged soil by means of an anchor cable inc
REFERENCES:
patent: 3151594 (1964-10-01), Collipp
patent: 3685479 (1972-08-01), Bruce
patent: 4019455 (1977-04-01), Hungerford
patent: 5474015 (1995-12-01), Bruce
BruPat Limited
Sotelo Jesus D.
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