Note: Descriptions are shown in the official language in which they were submitted.
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4 BACKGROUND OF THE INVENTION
1. FIELD OF INVENTION
6 This invention relates generally to a
7 stable support for structures at or above the surface
8 of a fluid medium and in particular to a
9 communications buoy for use in the ocean.
2. DESCRIPTION OF THE PRIOR ART
11 Many types of flotation devices exist with
12 differing characterisitcs.
1~ Damper plates and toroid shaped flotation
14 devices have been used to create buoys which are wave
followers. For example, see Buoy Engineering, H.O.
16 Berteaux, John and Sons, 1976 Pg. 212-213. These
17 surface following buoys are subject to strong heave
18 and pitch due to the motion of the ocean.
19 A more stable buoy can be built by
decreasing the cross section of the buoy at the water
21 level~ Such devices experience less heave. The mass
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1 of the buoy can also be distributed to create a
2 righting moment. This will decrease the pitch.
3 Further stability can be obtained by
4 surface decoupling. A bouyant cylinder with a
counterweight suspended from its bottom is a typical
6 example, Berteaux, supra. Such spar buoys cannot have
7 mucl- reserve bouyancy and usually have a large draft.
8 These factors mitiyate the usefulness of these types
9 of buoys in deep water.
3. SUMMARY OF THE IN_ENTION
11 It is an object of this invention to
12 provide a communications bouy having an antenna which
13 uses the surface of the ocean as a ground plane; such
14 bouy having structure which limits the antenna's
motion with respect to the surface of the ocean to
16 within 4 inches heave and 25 pitch.
17 It is another object of this invention to
18 provide a stable bouy that can withstand ocean
19 conditions up to and including state 5.
The buoy according to the invention may be
21 used as part of a search and rescue system for
22 locating downed aircraft and ships in distress. Such
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1 buoys would be carried by vehicles and be deployPd
2 when needed. Their distress siynal could be received
3 by satellites and their position located.
4 The bouy according to the invention could
carry various other types of payloads or support
6 various antenna structures as well. Other possible
7 uses include oceanographic monitoring buoys and
8 satellite linked sonobuoys.
9 It is an object of this invention to
provide an apparatus for the stable support of a
11 structure, such as an antenna, in a fluid medium, such
12 as water.
13 It is a futher object of this invention to
14 limit the motion of an antenna supported above the
surface of the ocean) within the operational limits of
16 the transmitting system.
17 It is a further object of this invention
18 to support an electronics payload near the surface of
19 the ocean such that the power loss between the
electronics payload and an antenna supported on the
21 surface is within operational limits and,
22 specifically, less than 3db.
23 The invention is an apparatus for the
24 stable support of a structure, such as an antenna, in
1 a fluid medium, such as water. The apparatus
2 comprises a bouyant first member and first means for
3 engaging the structure. The first means is associated
4 with the member. Second means are provided for
channeling the fluid which encroaches upon the bouyant
6 mem~er due to any motion of the member with respect to
7 the surface of the fluid medium, the encroaching fluid
8 being channeled back into the fluid medium such that
9 the kinetic energy of the bouyant first member is
dissipated as the fluid is channeled back into the
11 fluid medium.
12 Alternatively, the apparatus according to
13 the invention may comprise a bouyant first member for
14 supporting the structure, a payload and decoupling
means for supporting the payload below the bouyant
16 member such that any motion of the payload is
17 decoupled from the member and any motion of the member
18 is decoupled from the payload.
19 Alternatively, the apparatus according to
the invention may comprise a bouyant member with an
21 inwardly arched bottom portion, and means! associated
22 with the bouyant member, for engaging the structure.
23 Alternatively, an apparatus according to
24 the invention may comprise an antenna, a bouyant
member, first means for generating an r.f. signal,
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1 second means interconnecting the first means and the
2 antenna, and decoupling means for supporting the first
3 means below the bouyant member such that any motion of
4 the member is decoupled from the first means and the
motion of the first means is decoupled from the
6 member.
7 Alternatively~ the invention may comprise
8 a communications bouys which is stable in a fluid
9 medium and includes structures for minimizing the
heave and pitch of the bouy. Specifically, a
11 flotation bag with a concave bottom formed by pulling
12 in the center of the bottom of the bag with straps
13 secured to the inside walls of the bag supports an
14 antenna. A semi-rigid damper skirt extending around
the base of the bag is submerged when the apparatus is
16 floating in the fluid medium. The bag is provided
17 with a ribbon fence comprising containers which have
18 an opening above the fluid level, and an opening below
19 the fluid level, when the apparatus is floating in the
medium, allowing the fluid to flow in and out of the
21 containers. The payload is supported in a cylindrical
22 chamber connected to the flotation bag by a flexible
23 cable, enabling the payload to swing.
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1 BRIEF DES~RIPTION OF THE DRAWINGS
2 Fiyure 1 is a side view of a
3 communications bouy according to the invention
4 deployed in water.
Figure 2 is a side view of the bouy of
6 Figure 1 with parts broken away to illustrate internal
7 structure.
8 Figure 3 is a perspective view of a
9 communications bouy according to the invention in an
undeployed state.
11 Figure 4 is a top view of a flotation bag
12 according to the invention.
13 Figures 5a -59 are graphs illustrating the
14 operational transmission requirements and the
estimated performance of an antenna system according
16 to the invention under varying conditions of heave and
17 pitch.
.
18 DETAILED DESCRIPTION OF THE INVENTION
19 Referring to figures 1 and 2, flotation
bag 1 is an inflated balloon-like structure having a
21 specific gravity less than the specific gravity of
22 fluid medium W. Bag 1 encloses antenna 2 and supports
23 a payload 3 below the surface of medium W.
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3~
1 Although this embodiment comprises
2 flotation bag 1 which encloses antenna 2, the
3 invention includes flotation devices of any type which
4 support structures.
Figures 5a-5y compare the estimated
6 performance lû2 of an antenna such as antenna 3 under
7 varying conditions of heave and pitch with the
8 operational performance requirement 101 for successful
9 transmission. Antenna 3 uses the surface of the fluid
W as a ground plane. Heave and pitch disturb the
11 relationship between the radiating antenna 3 and the
12 ground plane, changing the radiation pattern of
13 antenna 3. As shown by graphs 5a, 5b, and 5f, the
14 estimated performance 102 of antenna 3 crosses and
falls below the operational performance requirements
16 for successful transrnission between points lû3 and
17 lG4. In summary, successful transmission is not
18 achieved when antenna 3 undergoes more than 4 inches
19 heave or 25 pitch. The apparatus according to the
invention limits the motion of the antenna relative to
21 the ground plane to within 4 inches heave and 25
22 pitch, under ocean conditions up to sea state 5.
23 A damper skirt 4 extends around the base
24 of the flotation bag 1 and is made of a semi-rigid
material supported in a horizontal position by ribbon
26 fence 5.
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1 When the apparatus is afloat, damper skirt
2 4 is ~elow the surface of the medium W. The weight of
3 the payload 3, the shape of the bottom of the
4 flotation Dag 1 and the bouyancy of bag 1, which will
be described in detail below, are configured so that
6 damper skirt 4 is below the water line when the
7 apparatus is stable.
8 Damper skirt 4 increases the surface area
9 in contact with the ocean, offering a surface which
resists motion V within medium W. In order to rise or
11 tip in response to a wave, damper skirt 4 must travel
12 upwardly through the fluid. The resistance to upward
13 movement of skirt 4 is caused by the fluid above the
14 skirt 4. The energy that would otherwise cause heave
and pitch of the flotation bag 1 is dissipated by this
16 resistance and any resulting movement of skirt 4
17 within the medium W.
18 As shown particularly in figure 4, ribbon
19 fence 5 which supports the damper skirt 4 is a series
of contiguous compartments, 5a-5g. Damper skirt 4
21 acts as the base of the compartments 5a-5g of ribbon
22 fence 5 and the side ls of the flotation bag 1 forms
23 the back wall of the compartments. The walls of the
24 compartments in the embodiment illustrated comprise a
strip of semi-rigid material connected to the side of
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1 the flotation bag 1 at spaced apart points P. The
2 flotation bag 1, damper skirt 4 and the strip form the
3 contiguous compartments, the combination of which is
4 referred to herein as ribbon fence 5.
Each compartment 5a-5g has an opening 6 in
6 the lower portion thereof, where the strip joins to
7 damper skirt 4. The compartments have an opened top
8 7. When sta~le in the ocean, the bottom hole 6, which
9 has a cross section less than the opening at the top
7, is beneath the level of the medium W. The water
11 line on the flotation bag when the apparatus is at
12 rest in the ocean is approximately at the midpoint 8
13 of the height oF the ribbon fence 5.
14 Compartments 5a-5h act as containers for
the fluid medium. Fluid encroaching upon bag 1 can
16 enter the compartments through hole 6 or the opened
17 top 7 and can drain from the compartments through the
18 hole 6. When bag 1 rises due to the motion of the
19 ocean, sea water will drain out of the holes 6,
dissipating the kinetic energy of bag 1 created by the
21 rising motion of the ocean. Oscillating of the
22 ~lotation bag 1 within the medium W are thereby
23 damped. The compartments increase the resistance to
24 motion of damper skirt 4 by partially enclosing the
fluid and by requiring the damper skirt to lift the
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1 partially enclosed fluid in the compartments as the
2 flotation bag 1 rises in response to a wave. This
3 acts to further decrease the heave and pitch of the
4 flotation bag.
S The damper skirt 4 and ribbon fence 5 are
6 described associated with each other, constructed from
7 semi-rigid materials for the purpose of stabilizing
8 flotation bag 1. However, the damper skirt 4 may be a
9 submerged plate and the means for channeling fluid
that encroaches on the device. Such structures may be
11 used separately or in combination to decrease both the
12 heave and pitch of the device.
13 Payload 3 comprises electronics 31
14 enclosed in a cylindrical housing 32. Housing 32 is
connected to the bottom of the flotation bag 1 by
16 nylon cord 8. One end of nylon cord 8 connects to a
17 point 8a within the housing, approximately one-quarter
18 from the top of the housing and the other end connects
19 to the center of the bottom of the bag 8b, at bulkhead
9, which is a rigid portion. Electrical wires 311
21 also pass from the electronics 31 into the bulkhead
22 9. Beneath the bulkhead 9 is microphonics bumper 91.
23 Nylon cord 8 and the location of the
24 connection between the housing 32 and the flotation
bag 1, at 8a and 8b, decouple the motion of flotation
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1 bag 1 from housing 32 such that, over a certain range,
2 the motion of bag 1 does not affect the motion of
3 cylindrical housing 32 and the motion of cylindrical
4 housing 32 does not affect the housing motion of bag
1. The range of motion depends on the demensions of
6 the decoupling apparatus including the diameter of
7 housing 32 and the distance between the top of housing
8 32 and microphonic bumper 91.
9 Housing 32 is free to swing like a
pendulum until the top of the housing 32a collides
11 with the microphonic bumper 91. Similarly, the
12 flotation bag 1 can freely pitch until the bumper 91
13 collides with the top of the housing 32a.
14 This allows for 10 - 15 of motion
of the payload 3, measured from the vertical, before
16 contact between housing 32a and microphonic bumper
17 91. Bumper 91 absorbs some of the energy of any
18 impact between bag 1 and payload 3, decreasing the
19 effect such impact would have on the heave and pitch
of the flotation bag. Bumper 91 also protects the
21 electrical wiring that feed to the antenna, preventing
22 interruption or interference with the transmission of
23 a message due to impacts between the housing 32a and
24 the bulkhead 9 through which wires 311 pass.
In the embodiment illustrated, electronics
26 31 is close to antenna 2 in order to minimize the
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~ po~er loss due to transmission of a signal from
2 electronics 31 to antenna 2 via cable 311.
3 Preferably, the power loss is less than 3db.
4 The upper portion 33, of housing 32,
referred to herein as a collar, stores the entire
6 flotation apparatus before it is deployed, as shown in
7 Figure 3. After deployment, the upper portion 33
8 floods with water, through holes 121 in its sides, as
9 shown in Figures 1 and 2. The flooding reduces the
bouyancy of the payload 3 which results in payload 3
11 pulling the flotation bag 1 into the water, ensuring
12 that the damper skirt 4 and bottom hole 6 of ribbon
13 fence 5 are submerged. This increases the stability
14 of flotation bag 1.
The flooding of upper portion 33 results
16 in the center of mass of housing 32 being lower in the
17 medium W, increasing the period of oscillation of
18 housing 32. This staoilizes the entire structure and
19 decreases the heave and pitch of flotation bag 1.
The center of the bottom of the flotation
21 bag 1 is pulled upward by straps 13 secured at 131,
22 along the inside wall of flotation bag 1. This
23 reduces the bouyancy of bag 1, aiding in maintaining
24 the necessary waterline above damper skirt 4 and at
the midpoint of ribbon fence 5. The base of bag 16 is
1 inwardly arched at its center 15 so that the greatest
2 bouyant forces are located at the outer portions of
3 the bag 16. This decreases the pitch of the flotation
4 bag 1 by creating a lonyer torque arm which must be
overcome for the flotation bag to rotate. This
6 riyhtiny moment further aids in stabilizing the
7 flotation bag. The adhesion caused by inwardly arched
8 center 15 between the surface of the bottom 16 of the
9 bag and the fluid medium W also decreasès the heave of
the flotation bag.
11 Although this particular embodiment
12 describes a flotation bag with a concave bottom, the
13 invention is meant to cover flotation devices of any
14 material with a bottom of inwardly arched shape.
The apparatus and payload are ejected in
16 the cylindrical housing 3, as shown in Figure 3.
17 Antenna 4, flotation bag 1, ribbon fence 5 and damper
18 skirt 4 are all stored in upper chamber 33 of the
19 housing 32. Houslng 32, which is bouyant, floats to
the surface of the ocean after being ejected. The
21 flotation bag and antenna are then deployed and the
22 preprogrammed messages are transmitted.
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