Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – With protection or indication of pipe or trench
Patent
1981-09-15
1984-09-04
Purser, Ernest R.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
With protection or indication of pipe or trench
405211, F16L 5700
Patent
active
044694687
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a device for lifting a moving object in a curved movement, in order, for example, to prevent damage to another object placed underneath the device.
An important field of application of the invention is protection of submarine installations such as pipelines and cables from damage due to dragging ships' anchors and fishing gear.
BACKGROUND ART
Several types of covers to protect submarine pipelines have been devised. U. K. Pat. No. 1 535 170, for example, discloses a cover with one hinge along its centerline.
To achieve the desired pivot of the cover around one of its two supporting edges and thereby lift of the anchor over the pipeline, if a ship's anchor catches hold of the other edge, a strong reactionary horizontal force against the first-mentioned edge, however, is required.
With only one hinge along the centerline of the cover such strong reaction will occur only in special cases, e.g. when at least two parallel covers are placed close against each other. In the ordinary case the anchor chain will prevent upward movement of the central portion of the cover.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a device that can lift a moving object also in cases where the local conditions do not provide for such reactionary force against pivot of the device.
The principle of the present invention is to utilize the frictional resistance to a much farther extent than the known prior systems do.
In the following description and in the drawings the invention will be illustrated by way of the example of a submarine pipeline to be protected from damage due to dragging ships' anchors.
The protective system comprises an upwardly convex covering plate placed over top of the pipeline, so that the plate rests on its two longitudinally extending edges.
Due to several longitudinally extending hinges in the cover, or a specially designed unstable structure of it, the cover to a certain point is easily deformed by horizontal forces over a certain impetus.
If an anchor is dragged across the pipeline, the flukes of the anchor may catch hold of the edge of the cover. Hereby the cover will deform. The tangential point of its surface in which the anchor chain leaves the cover will rise and shift to a higher point nearer to the edge opposite the anchor.
The resulting force acting on this edge thereby will become steeper, so that the frictional resistance between the edge and the ground can be utilized to withstand the horizontal drag of the anchor chain.
Due to the moment of this drag about this edge, the cover consequently will turn around this edge and hereby lift the anchor in a curve over the pipeline, so that damage to this is prevented.
The removed section of the cover thereafter has to be repositioned.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-section of a pipeline protected by a covering device in accordance with the invention,
FIG. 2 is the same as FIG. 1, but the cover is here deformed by a dragging anchor,
FIG. 3 is a cross-section of an alternative structure of the device according to the invention,
FIG. 4 is a cross-section taken along the line I--I of FIG. 5 of another alternative structure of a device covering a pipeline,
FIG. 5 is a plan view on enlarged scale of the device shown in FIG. 4,
FIG. 6 is a cross-section on enlarged scale of a special type of hinge,
FIG. 7 is a cross-section on enlarged scale taken along the line II--II in FIG. 8 of an alternative type of hinge,
FIG. 8 is a plan view on enlarged scale of the hinge shown in FIG. 7.
BEST MODE OF CARRYING OUT THE INVENTION
Consider a case where the ground consists of a non-clayey kind of soil, e.g. sand, which cannot provide sufficient resistance 7 to horizontal forces, so as to allow for the desired lift of a dragging anchor 10 hooking the edge 5 of the cover 3, FIGS. 1-2.
By use of the present type of cover, the deformation of this will cause the direction of the resultant 14 acting on the edge 6 opposite the anchor 10 to change to such degree that the
REFERENCES:
patent: 4077222 (1978-03-01), Larsen
patent: 4242010 (1980-12-01), Gjerde et al.
Hjorth Beverly E.
Purser Ernest R.
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