Ships – Mooring device – Having ship-mounted turret
Reexamination Certificate
2000-10-06
2001-07-24
Avila, Stephen (Department: 3617)
Ships
Mooring device
Having ship-mounted turret
C441S003000
Reexamination Certificate
active
06263822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to turret moored offshore vessels and in particular to a radial elastomeric spring arrangement for the main bearing of a mooring turret to compensate for hull deflections or distortions of the moored vessel.
2. Description of the Prior Art
Heretofore, elastomeric springs have been provided for supporting an upper bearing of a mooring turret for a moored vessel. For example, U.S. Pat. No. 5,515,804 dated May 14, 1996 shows a bearing support for a mooring turret in which a plurality of equally spaced resilient support structures support the upper bearing. Each support structure includes a post secured to the turret and extending downwardly from the turret at a 45 degree angle with a plurality of elastomeric shear pads between upper and lower post portions of each post The heavy weight of the mooring chains causes bending of an upper hull beam and the shear pads in the posts may move closer together or further apart as a result of unequal forces from the mooring chains.
Other elastomeric arrangements for reacting radial loads or forces from a turret mounted on a main bearing have included a plurality of radially extending support members mounted about the turret and having elastomeric bumper pads between the turret and hull of the moored vessel. The elastomeric bumper pads act as shock absorbing devices to assist in limiting radial deflection of the turret.
3. Identification of Object of the Invention
A principal object of the invention is to provide a radial spring arrangement between main bearing of a mooring turret and a vessel which compensates for ovaling of the vessel due to environmental forces at sea on the vessel.
SUMMARY OF THE INVENTION
The spring arrangement of the present invention includes a radial spring subassembly comprising a plurality of radially extending elastomeric springs spaced around the main turret bearing to react radial turret loads into the hull of the moored vessel and to isolate the turret from ovaling of the hull or body of the moored vessel. Ovaling of the hull of the vessel is caused by environmental forces on the vessel in heavy sea conditions. Each radial spring subassembly is moimted between the main bearing for the turret and the hull of the moored vessel The radial spring subassembly according to the invention includes a pair of concentric telescoping cylinders with one cylinder secured to the vessel and the other cylinder secured to an end plate for the elastomeric member and movable with the elastomer member. The telescoping cylinders which slide relative to each other, are effective for transmitting compressive loads and shear loads to the elastomeric member but not tension loads. The radial spring subassembly reacts the radial turret loads at the upper main bearing of the turret and also reacts the torsional loads of the main bearing resulting from bearing friction. The elastomeric pad of the radial spring subassembly is subjected to shear loads upon axial movement of the turret. The radial springs do not have enough lateral stiffness to absorb the entire axial load even although they do absorb part of the axial load.
REFERENCES:
patent: 4955310 (1990-09-01), Pollack
patent: 5052322 (1991-10-01), Poldervaart et al.
patent: 5306186 (1994-04-01), Boatman
patent: 5356321 (1994-10-01), Boatman et al.
patent: 5515804 (1996-05-01), Pollack
patent: 5839387 (1998-11-01), Myklebust
patent: PCT 96/27522 WO (1996-09-01), None
Boatman L. Terry
Fontenot William L.
Hobdy Miles A.
Avila Stephen
Bush Gary L.
FMC Corporation
Mayor Day Caldwell & Keeton, LLP
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