Hydraulic and earth engineering – Marine structure or fabrication thereof – Structure protection
Reexamination Certificate
1999-07-23
2001-09-04
Bagnell, David (Department: 3673)
Hydraulic and earth engineering
Marine structure or fabrication thereof
Structure protection
C405S211000, C405S212000, C405S213000, C114S219000, C114S220000, C293S107000, C293S108000
Reexamination Certificate
active
06283677
ABSTRACT:
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatuses for absorbing impact from structures, more particularly to such methods and apparatuses which are mented at berthing locations for absorbing impact from marine (vessels.
“Fenders” are bumpers which are utilized at docks, wharves, piers, moorages and anchorages for absorbing kinetic energy of berthing marine vessels. A fender absorbs kinetic energy of the berthing vessel by converting the kinetic energy into potential energy in the fender material system.
Fender systems have been used, or considered for use, wherein the potential energy is realized essentially in at least one of the following forms: deflection of a fender pile; compression of a rubber fender component; deformation of a foam-filled fender; torsion of a fender's cylindrical shaft; pressurization of a pneumatic fender; fluid motion/pressurization of a hydraulic fender.
Foam-filled fenders generally comprise a resilient, closed-cell foam wrapped with an elastomeric skin. The cellular structure of the foam reacts like individual pneumatic fenders by absorbing energy through deformation. The foam-filled fenders have high energy absorbing capabilities with relatively small reaction force and can float with the tide, handling several surface ship types. Since foam-filled fenders are typically large, they can act as a separator and provide a good standoff.
The U.S. Navy is currently utilizing composite materials in the fabrication of foam-filled fenders for berthing ships. The current design of a foam-filled fender for U.S. Naval ships includes a cylinder having a urethane foam core, overwraps of nylon, and a urethane sprayed over the cylindrical surface. The U.S. Navy's foam-filled fender system has demonstrated effectiveness in terms of reacting certain kinds of ship loads against piers, but has yet to be engineered for generic applications.
The U.S. Naval fenders currently in use are fabricated for a particular class of ship. U.S. Naval vessels which are characterized by different displacements require different fenders to be employed; one reason for this has been the U.S. Navy's need to ensure that a particular U.S. Naval ship's hull loading is maintained below a specific level. Furthermore, fenders of current U.S. Naval design are fixed in terms of the amount of energy which can be reacted. In order to absorb more energy, more or larger current U.S. Naval fenders are required.
Although the U.S. Navy's current foam-filled fender design has been successful in certain modes of practice, it does not lend itself to an analytical design methodology using current design tools. The method for fabricating the U.S. Navy's current foam-filled fender includes wrapping a urethane foam core with nylon fiber, and spraying urethane onto the fiber as it is wound onto the urethane core material; this technique results in operator-to-operator variance in urethane coating thickness or fiber volume fraction.
Accordingly, the mechanism of energy absorption cannot be accurately modeled for current U.S. Navy foam-filled fender systems. The efficacy of a given U.S. Navy foam-filled fender for a particular application requires independent empirical verification. Due to this incapability of advance fender design, the U.S. Navy's current foam-filled fender system necessarily lacks the versatility to predictably adapt to various configurations of marine vessel and/or berth.
Current U.S. Navy fenders are experiencing significant design overloads and are being replaced at an annual cost of millions of dollars per year. Moreover, many pier structures owned by the U.S. Navy and other entities are decrepit or dilapidated. Aging or deteriorating pier structures require renewed analysis to account for degrading mechanical properties. If analytical procedures are not soon established, existing pier structures may be prematurely replaced.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a bumper/fender system which can be used effectively for absorbing impact of a variety of marine vessels at a variety of berthing stations.
Another object of the present invention is to provide such a bumper/fender system which can be thus used for both large and small marine vessels.
It is a further object of this invention to provide such a bumper/fender system which admits of analytical modeling for purposes of predicting such varied usage.
A further object of this invention is to provide such a bumper/fender system which is economical.
The present invention is, to some extent, a “variation on a theme” disclosed by Crane et al. at the aforementioned copending U.S. application Ser. No. 09/012,007 which is incorporated herein by reference and of which this application is a continuation-in-part. The invention disclosed by Crane et al. at U.S. application Ser. No. 09/012,007 (hereinafter referred to as “Crane et al. '007”) was developed as part of Phase I of an SBIR (“Small Business Innovation Research Program”) project (OSD95-016). The present invention was developed as part of Phase II of the same SBIR project (OSD95-016). However the present invention represents an inventive improvement vis-a-vis' Crane et al. '007, and may be preferable thereto in many practical contexts.
Like the invention disclosed by Crane et al. at U.S. application Ser. No. 09/012,007 (hereinafter referred to as “Crane et al. '007”), the present invention provides a system for absorbing the impact of a relatively moving body. Also like the invention disclosed by Crane et al. '007, the present inventive system comprises a “bumper” which includes fiber-reinforced high strain-to-failure viscoelastic matrix material. Further like the invention disclosed by Crane et al. '007, the bumper is disposed in suspended fashion, either hanging or floating. Again like the invention disclosed by Crane et al. '007, upon impact by the relatively moving body the bumper reacts so as to strike against a closely situated structural entity.
Unlike the invention disclosed by Crane et al. '007, the present invention implements a “smart valve” for the bumper. Furthermore, unlike the invention disclosed by Crane et al. '007, the present invention obviates the need for one or more “deformers” for receiving the bumper after the bumper initially receives the body; energy is dissipated in a different manner. The present invention's bumper can react against any relatively rigid structural surface (such as a hard solid wall-like structure) which is part of any stable structure, such as a pier, dock, wharf, edifice, etc.
The present invention uniquely features a “smart” valve methodology which optimizes the load displacement curve of the inventive fender. The present invention also uniquely features utilization of a reusable winding mandrel in the fabrication of many embodiments of the inventive fender. In the light of the instant disclosure and the disclosure by Crane et al. '007, the ordinarily skilled artisan will appreciate the substantial extent of applicability to the present invention of the teachings and principles according to Crane et al. '007, as well as the significant differences therebetween.
To elaborate, the inventive system according to many embodiments of Crane et al. '007 comprises at least two composite structures and at least one housing. Each composite structure includes fiber-reinforced high strain-to-failure viscoelastic matrix material. At least one composite structure is a bumper (e.g., a “cylindroid” bumper which includes a hollow cylindrical axially intermediate portion and two protuberant axially extreme portions) for initially receiving the body. At least one composite structure is a deformer, (e.g., a “tension tube”) for consequently
Corona-Bittick Kathleen A.
Crane Roger M.
Dorr Donald James
Slattery Kerry T.
Bagnell David
Kaiser Howard
Lee Jong-Suk
The United States of America as represented by the Secretary of
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