Winding – tensioning – or guiding – Loop forming
Reexamination Certificate
1999-08-02
2001-08-21
Rivera, William A. (Department: 3653)
Winding, tensioning, or guiding
Loop forming
C242S361200, C242S362000, C242S386000, C114S312000
Reexamination Certificate
active
06276625
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a subsea tether cable storage system for Remotely Operated Vehicles (ROV) and submersibles. More particularly, the present invention relates to a tether cable deployment, retrieval and storage system.
2. General Background of the Invention
A subsea Tether Storage System (TSS) is used to free the ROV submersible from the effects of surface sea conditions, in column currents and to facilitate vehicle tether handling and storage. To accomplish this, a high strength armored umbilical from the surface is secured to the TSS where it is connected to a smaller, lighter, more flexible and near neutrally buoyant cable (tether). This tether connects to the ROV to provide power, instrumentation and control from the surface through the armored umbilical without the weight and hindrance of the main umbilical. The ROV is initially deployed from the surface, mated and secured to the TSS as a single unit. The TSS is negatively ballasted to maintain tension on the umbilical for positioning and current bucking characteristics. Upon reaching a predetermined depth and location, the ROV is unmated and, under its own propulsion, proceeds to the work site to perform assigned tasks. Tether is deployed as needed to allow the ROV to traverse hundreds of feet. Sufficient slack is provided to prevent hindering the ROV and to eliminate adverse surface effects.
There are two basic types of submersible tether storage systems: the top hat, also known as the bottom entry, and the side entry cage or launcher. The top hat system secures on top of the ROV. Its configuration is generally cylindrical but can be rectangular in shape. In this type of system, the tether is stored on a reel or in a basket and is payed in and out from the bottom of the system at the ROV docking point. During deployment, the ROV is released from the system and swims downward and away to the work site under its own propulsion. The process is reversed for retrieval and docking. The second type of tether storage system, the side entry cage or launcher, is usually much larger and completely encloses and secures the ROV inside the system. In this case, the tether is stored on a powered reel. During deployment, the ROV is released and swims out of the system horizontally under its own propulsion. Again, the process is reversed for retrieval and docking.
There are tether storage systems which coil tether into a basket; however, they use bail arms and may not be able to take high line loads, such as would occur if the ROV loses power.
The following U.S. Patents are incorporated herein by reference:
U.S. Pat. No. 4,487,153
U.S. Pat. No. 3,715,068
U.S. Pat. No. 5,551,545.
BRIEF SUMMARY OF THE INVENTION
The Tether Storage System (TSS) of the present invention solves the problems confronted by ROV submersible tether cable handling and storage in a simple and straightforward manner. A cylindrically shaped TSS in a top hat configuration is used. This TSS unit eliminates the use of a rotary slip ring unit for transmission of electrical power and electronic data from the surface umbilical to the tether for power, instrumentation and control of the ROV. The invention accomplishes this by using fixed connections at the TSS and by handling the tether with a minimum amount of bending and twisting. A large round basket in the TSS facilitates tether storage while minimizing tether stress conditions. Elimination of a powered storage reel and a complex level wind reduces the bending, tension, compression, chafing, and twisting imposed on the tether. This results in lower stresses thus reduced wear and tear to increase tether reliability and life. Exclusion of the electrical slip ring assembly required by powered storage reels also increases reliability and greatly reduces costs.
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Chee Winston C.
Sherlin Thomas L.
Garvey, Smith, Nehrbass & Doody, L.L.C.
Rivera William A.
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