Ships – Anchor – Fluke type
Patent
1994-05-10
1996-08-20
Sotelo, Jesus D.
Ships
Anchor
Fluke type
114304, B63B 2132
Patent
active
055468837
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an anchor, comprising a fluke means with a surface centre of gravity and a front end or penetration end and a rear end, and a shank means, being connected at a first end to the fluke means and at a second end being provided with first means for attachment to an anchor line, said shank means being fastened by means of at least one hinged joint to the fluke means. The invention is furthermore directed to a method for anchoring objects with the aid of such an anchor.
An anchor of the type as described above is known from U.S. Pat. No. 3,450,088. The anchor disclosed by this document comprises a straight shank, being fastened at its first end by means of a first hinged joint to the fluke, as well as a coupling rod extending between a point halfway down the shank and a point disposed between the first hinged joint and the front end of the fluke. At its one end the coupling rod is hinged on the fluke and at its other end it comprises a pin, fitting in a recess in the shank that opens obliquely downwards, the coupling rod being secured to the shank there also by means of a breaking bolt. When the anchor that has penetrated the soil has to be weighed again, one pulls an anchor line attached to the second end of the shank in an essentially vertical direction. The soil disposed above the fluke will prevent the fluke from turning with a force that is great enough to cause the breaking boll to break. Subsequently the pin at the upper end of the coupling rod will also be twisted out of the recess, while the shank rotates upwards alone with the anchor line when this is pulled, the shank pivoting about the first hinged joint with respect to the fluke. The anchor can then be weighed by pulling the anchor line, whereby the shank, the fluke and the coupling rod are eventually hinged with respect to one another in such a fashion that they are essentially aligned.
In recent years, drilling platforms have been installed in increasingly deep waters, and as a result the length of the pertaining anchor lines has also increased. Drilling platforms are generally anchored by means of eight to twelve anchors of 10 to 15 metric tons each. If it is desireable to remove the anchors with which the drilling platform is moored with a view to relocating the drilling platform, it is often quite difficult and costly to remove the anchors with the aid of auxiliary vessels. One should be aware that the wave conditions may be rough to the extent that such operations cannot be performed at all. Therefore it has been attempted for a long time to develop an anchor whose holding power can be reduced at will, so that it can be weighed so much more easily.
An example of such an anchor is discussed in the foregoing. The drawback of this known anchor is that for weighing this anchor, a separate vessel is required still, for if one would pull the anchor line from the drilling platform with a view to weigh the anchor, then it is to be expected that the fluke, extending at an angle with respect to the shank which is suited for sand or mud, will twist around the front end of the fluke, whereby the fluke surface projected perpendicularly to the direction of pulling is increased and thus the pulling force required to pull the fluke further through the soil will have to be considerably greater than the original holding power supplied by the anchor. The construction of the known anchor is such that when the breaking bolt breaks it is not to be expected that the pin will leave the recess if the second end of the shank is not pulled essentially in the vertical direction.
The invention aims to provide an anchor of the type referred to in the introduction, which can easily be weighed from its penetrated condition from aboard a moored object, such as a drilling platform. For that purpose the anchor of the invention is characterized in that the said hinged joint with which the shank means is attached to the fluke means is disposed at a location either towards the front or towards the rear at a distance from the centre of gravity, and in that
REFERENCES:
patent: 4781142 (1988-01-01), Cheung
"New anchor designs" Oil and Gas Journal vol. 88, No. 29, 16 Jul. 1990, Tulsa p. 66.
Sotelo Jesus D.
Vrijhof Ankers Beheer B.V.
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