Fender with step and/or projection

Details Fender with step and/or projection Fender with step and/or projection

2000-12-20

2003-06-03

Lee, Jong-Suk (James) (Department: 3673)

Hydraulic and earth engineering

Marine structure or fabrication thereof

Structure protection

C405S211000, C405S215000, C114S219000

Reexamination Certificate

active

06572307

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a fender designed to protect a vessel by reducing the impact of the docking vessel through absorption of the kinetic energy thereof.
A fender
9
conventionally used in the art is exemplified by a circle-type fender made of one piece rubber material having a sectional shape as shown in FIG.
20
A. The circle-type fender
9
includes: a first bumper member
91
formed in a cylindrical shape of a constant outside diameter and constructed such that one end of the cylindrical body defines a distal end
9
a
of the fender
9
and serves as a fixing portion for fixing an impact receiving plate (not shown) directly coming into contact with a vessel; and a second bumper member
92
formed in a hollow conical shape wherein one end thereof is connected to the other end of the cylindrical body of the first bumper member
91
while the other end thereof defines a fix portion to be fixed to a fixing surface Q on a dock and wherein the latter end thereof has a greater outside diameter than the former end thereof. Indicated at
93
is a flange actually functioning to fix the fix portion of the second bumper member
92
to the fixing surface Q.
When receiving a compressive force from the docking vessel, the fender
9
is compressively deformed as described below. First, the fender
9
develops a reaction force against the compressive force. When the fender can no more withstand the compressive force, it starts to buckle at an outer periphery of a connection portion CP between the first bumper member
91
and the second bumper member
92
and at an inner periphery of a buckling position BP of the second bumper member
92
. Subsequently, as shown in
FIG. 20B
, the whole body of the fender
9
is deformed into a tightly folded shape with an outer periphery
91
a
of the first bumper member
91
and an outer periphery
92
a
of the second bumper member
92
as well as areas
92
b
,
92
c
above and below the buckling position BP on the inner periphery of the second bumper member
92
coming into contact with each other. Then, the tightly folded fender
9
with no more portion to be buckled forms a single rubber mass which is further compressively deformed.
If this process is expressed by a distortion-reaction force characteristic curve plotting the amount of distortion of the compressed fender
9
relative to the reaction force developed in the fender
9
, a solid curved line of
FIG. 21
is obtained. Specifically, a line portion between the origin O and Maximum Point A corresponds to a period between a normal state shown in
FIG. 20A and a
state just before the fender starts to buckle, yielding to the compressive force. During this period, the compressed fender
9
develops the reaction force, trying to restore itself to its initial shape. The reaction force increases as the amount of distortion becomes greater. Upon buckling, however, the fender
9
loses most of the reaction force. Hence, the reaction force declines during the time that the fender
9
is crushed into the state of FIG.
20
B. This time period corresponds to a line portion between Maximum Point A and Minimum Point C of the characteristic curve. In the state of
FIG. 20B
, the whole body of the fender
9
behaves as a single rubber mass as mentioned supra, developing the reaction force again. Therefore, the reaction force substantially linearly rises from Minimum Point C.
The practically useful range of the fender
9
with such a characteristic curve is limited to a range between the origin O and a point B representing the same level of reaction force as Maximum Point A. The useful range as expressed in terms of distortion is limited to the range of not more than D. This is because a distortion in excess of D means an excessive reaction force which, in turn, will cause damage to the vessel or to the fender
9
itself. The amount of energy that the fender
9
can absorb through distortion D within the allowed range is represented by an area S
1
of a region enclosed by the characteristic curve represented by the solid line, a horizontal axis O-D, and a vertical line B-D.
It is generally thought idealistic that the fender is capable of absorbing such an amount of energy that corresponds to the combination of the above area S, and an area S
2
of a region enclosed by the characteristic curve and a horizontal line A-B. However, the fender is actually capable of absorbing energy of an amount reduced by that represented by the area S
2
, thus reduced in the energy absorption efficiency.
In this connection, study has been made to increase the energy-absorption capacity of the fender
9
. For instance, it is contemplated to increase thicknesses T
1
and T
2
of the first and second bumper members
91
,
92
, as shown in
FIG. 22A
, thereby to increase the reaction forces of the bumper members
91
,
92
against compression.
Unfortunately, this approach has the following problem. With a smaller distortion than in the case of
FIGS. 20A
,
20
B, the fender
9
is buckled into a completely folded state, as shown in
FIG. 22B
, wherein the outer periphery
91
a
of the first bumper member
91
and the outer periphery
92
a
of the second bumper member
92
as well as the areas
92
b
,
92
c
above and below the buckling position BP on the inner periphery of the second bumper member
92
come into contact with each other, leaving no more portion to be buckled. That is, with a smaller distortion than in the case of
FIG. 20B
, the buckled fender
9
starts to behave as the single rubber mass.
As indicated by a dash-single-dot curved line in
FIG. 23
, this results in a smaller distortion D′ than the distortion D in the case of
FIGS. 20A
,
20
B, the distortion D′ corresponding to the reaction force which, after buckling, starts to re-increase and reaches a point B′ representing the same level as Maximum Point A′. That is, a width of a constant load area in which the fender is principally involved in the energy absorption, or the range A-B between Maximum Point A and the point B of the characteristic curve is reduced to a range A′-B′. Thus, the fender is reduced in the energy-absorption capacity after buckling.
Therefor, the arrangement of
FIG. 22A
suffers a problem that despite the increased size corresponding to the increased thickness as described above, the fender cannot attain the increased energy-absorption capacity corresponding to the size increase or any increase in the energy-absorption capacity at all.
SUMMARY OF THE INVENTION
A first object of the invention is to provide a novel fender capable of approximating a distortion-reaction force characteristic curve within an allowed range of distortion to an idealistic curve representing a substantially constant value of reaction force after the maximum point.
A second object of the invention is to provide a novel fender capable of presenting the greatest possible energy-absorption capacity within the allowed range of distortion.
According to the invention of claim 1, a fender for absorbing the impact of a vessel, formed of rubber and fixed to a fixing surface of a dock as having an impact receiving plate secured to a distal end of its body, the fender comprising: a first bumper member formed in a cylindrical shape of a constant outside diameter and defining at one end of the cylindrical body thereof a fixing portion for the impact receiving plate; a second bumper member connected at one end to the other end of the cylindrical body of the first bumper member, defining at the other end thereof a fix portion to be fixed to the fixing surface, formed in a hollow conical shape with its latter end greater in outside diameter than its former end, and buckling radially outwardly upon receiving a compressive force from the vessel thereby absorbing the impact of the vessel; and a step formed along an outer periphery of a connection portion between the two bumper members, the step defined by the former end of the second bumper member having a greater outside diameter than the latter end of the firs

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