Textiles: braiding – netting – and lace making – Processes and products – With material incorporated in diverse ways
Patent
1998-08-20
2000-07-11
Stryjewski, William
Textiles: braiding, netting, and lace making
Processes and products
With material incorporated in diverse ways
57210, 57907, 87 5, 87 13, 114230, 441 3, 441 23, D04C 112
Patent
active
060856289
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE OF RELATED APPLICATION
This is the national stage of International Application No. PCT/GB96/02222 filed Sep. 9, 1996.
BACKGROUND OF THE INVENTION
The present invention relates to buoyant rope assemblies, and particularly, though not exclusively, to buoyant rope assemblies for use in mooring.
Known flotation systems for single point mooring (SPM) hawsers generally take the form of a number of discrete floats laced or slid onto the rope. Such systems allow the hawser to remain flexible because of the relatively large separation between the floats, but do have problems. For example, bending tends to be concentrated in the portions of the rope between the floats, which can lead to premature fatigue of these portions. Also, the changing cross-section of the rope/float assembly can lead to snagging.
Rope assemblies are also known in which a central rope is surrounded by a buoyant layer of closed cell foam extending along the full length of the rope, with a protective outer layer thereabout. These assemblies reduce the problem of snagging and premature fatigue mentioned above, but have other problems. For example, the relative inflexibility of the assembly can lead to buckling and compression of the foam when the rope is severely bent, such as during reeling or packing. Also, the foam layer tends to stretch less than the central rope to which it is attached, and this can lead to cracking and/or separation of the foam. If cracking does not occur, the mismatch in extension may result in crushing of the foam, thereby reducing buoyancy. Further, a hawser generally experiences continually fluctuating loads due to wave action, and this cyclic loading can induce heat build-up in the rope, which is detrimental to performance and durability. The foam layer can act as an insulator and can prevent this heat from dissipating.
BRIEF SUMMARY OF THE INVENTION
The present invention aims to provide an improved buoyant rope, and, viewed from one aspect, provides a buoyant rope assembly comprising a central rope, a plurality of closed cell foam flotation elements spaced along the rope, and elements of open cell foam between the flotation elements.
The open cell foam elements will generally, although not necessarily, be substantially shorter than the flotation elements, and may be thought of as "spacer" or "buffer" elements between the flotation elements.
The positioning of a number of open cell elements between a number of discrete flotation elements provides a flexible rope assembly, and the compressible nature of the open cell foam helps to prevent crushing of the flotation foam during for example packing. Further, the open cell foam and flotation elements may be flush with one another to provide an overall assembly of substantially constant cross-section to avoid snagging problems.
The open cell foam is able to absorb water, and this water may be pumped into and out of the open cell elements by the cyclic loading of the rope caused by wave action. In this way, the water in the open cell elements may be continually replaced to thereby dissipate heat from at least the regions surrounding these elements. Thus, in rope according to the present invention, the cyclic loading action which actually heats up the rope assembly may also be used to pump water from the open cell foam elements to dissipate the heat. The rope assembly may be configured so that it allows water pumped from the open cell foam to circulate along the length of the rope to provide greater heat dissipation. For example, the water may pass along the central rope and/or between the central rope and the flotation elements.
The rope assembly preferably includes a flexible outer layer which may be used for example to protect against abrasion, and/or to hold the flotation and open cell elements in place. Where an outer layer is provided which is waterproof, vent holes or other means may be provided at the locations of the open cell elements to allow for communication with the water to provide the cooling effects mentioned above.
The rope assembly may
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patent: 3295489 (1967-01-01), Bossa
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patent: 3578763 (1971-05-01), Platou
patent: 3710409 (1973-01-01), Davidson
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patent: 4593599 (1986-06-01), Yeardley
patent: 4597351 (1986-07-01), Brainard
patent: 4640212 (1987-02-01), Brandt
patent: 4955012 (1990-09-01), Bledsoe et al.
patent: 5522674 (1996-06-01), Cooper
Clarke Christopher
Street Andrew John
Marlow Ropes Limited
Stryjewski William
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