Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: SELF-ADJUSTING WAVE BREAK
FIELD OF THE INVENTION
This invention pertains to floating breakwaters or break walls installed along
harbours to protect vessels moored in these harbours, and most particularly,
it
pertains to self-adjusting wave breaks that automatically expose a larger wave-
breaking surface when floating in larger waves. These break walls are also
installed to prevent soil erosion along shore lines.
BACKGROUND OF THE INVENTION
The efficiency of a breakwater depends on its ability to break up and scatter
waves without being lifted by these waves. This efficacy is difficult to
achieve
with a floating breakwater having a slack mooring line, in particular, because
upward forces from the breakwater's buoyancy tend to push the breakwater at
the surface of the wave.
In the past, at least two attempts have been made to design a floating wave
break that is intended to plunge through a wave to cut through and to disperse
the crest of the wave. These prior art wave breaks have no similarities with
the
wave break according to the present invention, but the prior art documents
describing these older breakwaters are nonetheless cited herein below simply
to illustrate the environment in which the present invention will be
described.
US Patent 335,032 issued to L.W. Leeds on January 26, 1886 discloses
different wave breaks, each having a floating structure and a wedge-like
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horizontal plow-bar, referred to as a cut-water, projecting forward from the
floating structure. The cut-water bar penetrates the waves along a horizontal
plane to break the force of the waves before they reach the floating
structure.
US Patent 3,952,521 issued to J. M. Potter on April 27, 1976 discloses an
elongated triangular structure supported on two tubular floats. The floats
have
airfoil-like fins on their sides to cause the floats to dig into the forward
side of
a wave and to retain the wave break against the lifting forces of the wave so
that the wave break can pass through the crest of the wave.
Although the devices of the prior art deserve undeniable merits, there is a
need
for a more efficient floating wave break which can be easily moved and
anchored with slack mooring lines.
SUMMARY OF THE INVENTION
In the present invention, there is provided a wave break that has an elongated
shape and three wave-breaking surfaces mounted thereon to form an elongated
triangular configuration. The wave break has a lazy side on its forward edge,
such that the force of the wave tilts it about the forward edge to increase a
projection of its wave breaking surfaces against the incoming wave.
More specifically, in one aspect of the present invention there is provided a
wave break that has an elongated structure with a triangular cross-section.
The
triangular cross-section has the shape of a right-angle triangle with a right-
angle side and an acute-angle side. The right angle shape is defined by three
elongated stringers from which a leading stringer is at the acute-angle side.
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The elongated structure also has three wave barrier surfaces extending there
along. Each of these wave barrier surfaces is made of a plurality of pipe
members spaced apart from each other and extending at right angle between
two of the afore-mentioned stringers.
Each of the stringers on the right-angled side, and each pipe member has a
sealed hollow configuration forming a floating vessel. The leading stringer
has added weight therein or open ends such that a buoyancy thereof is
substantially nil. The wave break also has a mooring line attached to the
leading stringer.
Because of the lazy forward side of the wave break, the leading stringer dive
into each wave without deviating substantially from a horizontal plane. The
trailing side of the wave break is subject to the lifting forces of each wave
and
therefore, the trailing side tilts upward and downward in use. The trailing
side
tilts upward and downward about the leading stringer to rotate the wave
breaking barriers of the wave break into a more or less perpendicular
alignment relative to the wave movement, for breaking the wave more
effectively.
Also, the wave break according to the present invention is relatively light
and
easy to transport and to install as compared to other breakwaters available
commercially.
This brief summary has been provided so that the nature of the invention may
be understood quickly. A more complete understanding of the invention can
be obtained by reference to the following detailed description of the
preferred
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embodiment thereof in connection with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention is illustrated in the
accompanying drawings, in which like numerals denote like parts throughout
the several views, and in which:
FIG. 1 is a perspective view of a breakwater made with self-adjusting wave
break segments according to a preferred embodiment of the present invention,
joined end-to-end;
FIG. 2 is an end view of a preferred wave break segment floating along the
hollow of a wave or on calm waters;
FIG. 3 is an end view of the preferred wave break segment floating through
a wave;
FIG. 4 is a reference illustration showing the period and amplitude of a wave;
FIG. 5 is an enlarged end view of the preferred wave break segment illustrated
in FIGS. 2 and 3;
FIG. 6 is a cross section view of one pipe member in the preferred wave break
segment as seen along line 6-6 in FIG. 5;
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FIG. 7 is a partial oblique view of the wave break segment as seen along line
7-7 in FIG. 5;
FIG. 8 is a cross-section plan view of the preferred wave break segment as
seen along line 8-8 in FIG. 5;
FIG. 9 is an enlarged view of the end of a wave break showing optional
structural variations that are within the scope of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The expression "wave break" is used by seamen to describe a wave breaking
structure protecting a harbour, and therefore it is also used herein for
convenience to describe the wave break structure according to the present
invention.
Referring firstly to FIG. 1, the preferred wave break 20 consists mainly of an
elongated openwork structure having a triangular cross-section. The openwork
structure is made of hollow pipes. The hollow pipes are preferably made of
plastic, but can also be made of metal tubes having a relatively thin wall.
The
preferred wave break 20 has a transportable length and is referred to herein
interchangeably as a wave break or a wave break segment. These segments are
joined to each other, atjoints 22, to form breakwaters 24 having lengths of 20
feet or more, for example.
These breakwaters 24 are anchored to the seabed by slack mooring cables 26
or chains. The expression "slack mooring cables or chains" is used here to
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describe a mooring system that allows the wave break 20 to rise and fall with
the tides. It will be appreciated that the tension of the mooring lines can be
adjusted to retain the leading stringer within a desired vertical
displacement,
according to wave heights and tides at the installation site.
These breakwaters 24 are installed in straight lines, or most preferably,
these
breakwaters are installed to form an arc having a convex side facing the
incoming waves, as illustrated in FIG. 1.
Referring now to FIGS. 2 and 3, the preferred wave break 20 is made of three
open planar frameworks connected to each other by three parallel longitudinal
stringers, in a right-angle triangular configuration. In use, the acute-angle
side
of the wave break 20 faces against the movement 28 of the waves as
illustrated.
The stringer on the leading edge of the wave break 20 is referred to as the
leading stringer 30. In use, a mooring line 24 is attached to the leading
stringer
30.
The stringer on the trailing edge is referred to as the trailing stringer 32,
and
the stringer on the upper edge is referred to as the upper stringer 34. The
open
framework extending between the leading stringer 30 and the upper stringer
34 is referred to as the first barrier surface 40. The open framework lying
between the upper stringer 34 and the trailing stringer 32 is referred to as
the
second barrier surface 42, and the open framework lying between the leading
stringer 30 and the trailing stringer 32 is referred to as the third barrier
surface
44.
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The preferred wave break 20 is made of cylindrical pipe members that are
sealed at ends and at all j oints so that they constitute hollow floating
structures.
The leading stringer 30 is weighted down with concrete 46 or other heavy
material so that the wave break 20 tilts forward in calm water. The leading
stringer 30 is weighted down or its ends are left open, so that its buoyancy
is
substantially nil and so that it remains submerged below the water surface, as
illustrated in FIG. 2 in calm waters. Using seamen language, the preferred
wave break 20 has a lazy forward side, which does not react or that is slow to
react to buoyant forces.
It should be understood that the weighing of the leading stringer 30 can also
be done partially or entirely by using heavy mooring chains 24 instead of
cables.
Because of the structural features of the preferred wave break 20, the leading
stringer 30 plunges into the waves 60 in rough waters, as illustrated in FIG.
3.
The buoyancy forces on the third barrier surface 44 and on the trailing
stringer
32 causes the wave break 20 to tilt forward when traversing a wave 60, thereby
reducing the angle `A' as illustrated in FIGS. 2 and 3. It will be appreciated
that the reduction of the angle `A' is in direct relationship with the height
of
the waves 60, because it varies directly with the portion of the wave break 20
that is submerged when a wave pass through the wave break 20.
The variation in the angle `A' is due to a rotation of the wave break 20 about
the leading stringer 30 in a direction `B'. A rotation of the wave break 20 in
the direction `B' causes the leading stringer 30 to dive through an incoming
wave 60 and causes the first barrier surface 40 to move toward a perpendicular
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alignment relative to the movement of the wave 60. Similarly, the tilting of
the
wave break 20 in the direction `B' causes the second and third barrier
surfaces
42, 44 to form converging fence-like surfaces across the movement of the
wave 60, as illustrated in FIG. 3.
As it can be understood, all three barrier surfaces 40, 42 and 44 cooperate
together to break up the waves 60 in two cascading steps. A first step
consists
of passing the wave through a quasi-vertical barrier to change the direction
of
the flow a first time, and the second step consists of passing the waves
through
the converging fence-like surfaces, for changing the direction of the wave a
second and third times.
After the passage of a wave 60 through the wave break 20, the wave break 20
returns back to its initial attitude as illustrated in FIG. 2. The buoyancy
forces
on the preferred wave break 20 cause the wave break 20 to tilt back and forth
and to self-adjust to the height of the wave entering into its barrier
surfaces 40,
42and44.
In high waves, the first barrier surface 40 rotates toward a vertical
alignment,
thereby presenting a maximum degree of resistance to the incoming wave 60.
Because of the triangular cross-section of the wave break 20, the buoyancy
forces on the second and third barrier surfaces 42, 44 generate a torque about
the leading stringer 30, to force the first barrier surface 40 to move toward
a
vertical alignment. This torque increases with the degree of immersion of the
wave break 20. Similarly, this torque causes the second and third barrier
surfaces 42, 44 to move toward a funnel-like alignment where both surfaces
converge together and contribute substantially equally to the breaking-up of
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the wave 60.
The expression "self-adjusting" in the description of the present invention
comes from the fact that the wave break 20 tilts back and forth about the
leading stringer 30, to increase or to decrease the aggressiveness with which
the wave-breaking surfaces thereof are oriented in response to the height of a
wave being penetrated.
Referring now to FIGS. 4 - 9, additional structural details of the preferred
wave break 20 will be described.
In a preferred embodiment, each barrier surfaces 40, 42, 44 is made of spaced-
apart parallel pipe members each having a same diameter as the longitudinal
stringers 30, 32, 34. The pipe members forming the first surface barrier 40
are
labelled as pipe members 70. The pipe members labelled as 72 form the
second surface barrier 42, and the pipe members labelled as 74 form the third
surface barrier 44.
The preferred length of the pipe members 74 forming the third surface barrier
44 or the base of the wave break 20 is preferably one quarter (1/4) of the
period `P' of typical waves found at the location where the wave break 20 will
be installed. The length of the pipe members 72 forming the second surface
barrier 42 or the height of the wave break 20 is preferably the same dimension
as a typical wave height `H' found at the location where the wave break will
be installed.
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Typical dimensions for the length of the pipe members 72, 74 and 70 are six,
eight and ten feet respectively, and the diameter of each pipe member is about
twelve to sixteen inches. The dimensions of the pipe members in the preferred
wave break 20 are adjusted according to the severity of the conditions where
the wave break will be installed. These dimensions are adjusted according to
factors such a wave height, wave period, water current and the length of the
breakwater 24 to be formed.
Each of the barrier pipe members 70, 72 and 74 has fins 76 on its sides as
illustrated in FIG. 6. The purpose of these fins in the first barrier surface
40
is to deflect water sideways and against one of the pipe members 72, 74 in the
second and third barrier surfaces 42, 44. The purpose of the fins 76 on the
pipe members 72, 74 is to deflect water sideways and create turbulence behind
the wave break 20 to further break up the waves 60 after these waves have
passed through the wave break 20.
The preferred spacing `S' of pipe members 70, 72 or 74 along a same barrier
surface 40, 42 or 44 is about at least twice as much as the outside diameter
of
one pipe member. The preferred spacing of pipe members in one barrier
surface from the pipe members in an adjacent barrier surface is about the same
as the diameter of one pipe member, such that the pipe members in one surface
barrier is offset the distance of one pipe member from the pipe members in an
adjacent barrier surface.
The width of the fins 76 on each of the pipe members 70, 72, and 74, is equal
to or less than the radius on one pipe member, such that the effective width
`W' of each pipe member, as shown in FIG. 6, is about twice or slightly less
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than twice the diameter of one pipe member. The effective width `W' of each
pipe member is also determined taking into account the water current present
at the location where the wave break 20 will be installed. The effective width
`W' is selected so that the drag created on the wave break 20 by the water
current does not prevent an effective tilting of the wave break 20 as
described
herein.
Similarly, the inclination `C' of the fins 76 can vary from 0 to 60 and this
angle is also determined according to the severity of the conditions at the
installation site.
Referring now to FIG. 9, this illustration will be used to explain two
structural
variations which should be considered to be withing the scope of the present
invention. As mentioned before, the stringers 32 and 34 on the right-angle
side of the wave break 20 have closed ends so that they act as floating
vessels.
In order to further increase the buoyancy of the wave break 20, and to further
promote a rotation of the wave break 20 about the leading stringer 30, the
trailing stringer may have a larger diameter than the other stringers, as
illustrated by label 32' in FIG. 9. Also, as mentioned before, the leading
stringer 30 may have open ends as indicated by label 30', so that its buoyancy
is substantially nil.
The dotted lines in FIGS. 7, 8 and 9 indicate a repetition of the pipe member
arrangements over the full length of a wave break segment 20.
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