U.S. patent number 3,818,523 [Application Number 05/190,019] was granted by the patent office on 1974-06-25 for subsurface current utilizing buoy system.
This patent grant is currently assigned to Sanders Associates, Inc.. Invention is credited to Stephen L. Stillman, Jr..
United States Patent |
3,818,523 |
Stillman, Jr. |
June 25, 1974 |
SUBSURFACE CURRENT UTILIZING BUOY SYSTEM
Abstract
A sonobuoy system is described in which the buoy proper is
anchored by a slack cable from which an array of hydrophones is
suspended. The sonobuoy is deployed beneath the surface and its
depth is controlled by varying the attitude of the buoy so that
ocean currents, which are present virtually everywhere in the sea,
act on the buoy to generate positive or negative lift thereby
increasing or decreasing the depth in accordance with a
predetermined program or on command. Vanes attached to the buoy
augment the lift of the body of the buoy. Attitude is changed by
pumping water between fore and aft tanks. Provision is made for
bringing the buoy to the surface from time to time to abstract the
information which has been gathered.
Inventors: |
Stillman, Jr.; Stephen L.
(Hollis, NH) |
Assignee: |
Sanders Associates, Inc.
(Nashua, NH)
|
Family
ID: |
22699726 |
Appl.
No.: |
05/190,019 |
Filed: |
October 18, 1971 |
Current U.S.
Class: |
441/22; 114/333;
367/4 |
Current CPC
Class: |
G10K
11/006 (20130101); B63B 22/18 (20130101); B63B
2207/02 (20130101) |
Current International
Class: |
B63B
22/00 (20060101); B63B 22/18 (20060101); G10K
11/00 (20060101); B63b 021/52 () |
Field of
Search: |
;9/8 ;114/16E,235B
;244/33 ;102/13,14 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blix; Trygve M.
Assistant Examiner: O'Connor; Gregory W.
Attorney, Agent or Firm: Etlinger; Louis Hunter; William
L.
Claims
What is claimed is:
1. A buoy system for deployment in a body of flowing water,
comprising,
a housing,
an anchor,
a slack cable interconnecting said housing and said anchor, and
means responsive to a signal for varying the lift produced by the
flow of water over the surface of said housing.
2. A buoy system in accordance with claim 1 in which said means for
varying includes means for varying the attitude of said
housing.
3. A buoy system in accordance with claim 1 in which said signal is
indicative of water pressure incident on said housing, whereby the
depth may be controlled.
4. A buoy system in accordance with claim 1 in which said housing,
its contents and the cable have an overall positive buoyancy.
5. A buoy system in accordance with claim 1 which includes vanes
attached to the exterior of said housing to increase the lift.
6. A buoy system in accordance with claim 1 in which said signal is
indicative of depth.
7. A buoy system in accordance with claim 1 in which said signal is
an externally originating command.
8. A buoy system in accordance with claim 1 in which said signal is
indicative of acceleration.
9. A buoy system in accordance with claim 1 in which said signal is
indicative of vertical acceleration above a threshold level caused
by surface waves.
10. A buoy system in accordance with claim 1 in which said signal
is indicative of a predetermined program.
11. A buoy system in accordance with claim 10 in which said program
includes a command to bring said housing to the surface.
12. A buoy system in accordance with claim 11 including means for
detecting a rough condition of the sea surface upon ascent and
means responsive to the detection of a roughness exceeding a
predetermined threshold for overriding a command to bring said
housing to the surface and for commanding said housing to
descend.
13. A buoy system in accordance with claim 1 in which said cable is
connected to said housing by means of a bridle fastened near
opposite ends thereof.
14. A buoy system in accordance with claim 1 in which said cable
includes conductors for the transmission of data and power.
15. A buoy system in accordance with claim 1 in which said means
for varying includes means for maintaining said housing at a
predetermined depth.
16. A buoy system in accordance with claim 1 which includes a
plurality of hydrophones supported by said cable.
17. A buoy system in accordance with claim 16 having means
including an antenna for transmitting the information received by
said hydrophones.
18. A buoy system in accordance with claim 17 in which said means
for varying includes means for bringing said housing to the surface
of the water to transmit said information.
19. A buoy system in accordance with claim 18 which includes a gas
tight bag, means for inflating said bag when said housing is on the
surface and means for mounting said antenna on the upper portion of
said bag.
20. A buoy system in accordance with claim 1 in which said means
for varying includes means for varying the distribution of the
weight within said housing.
21. A buoy system in accordance with claim 20 in which said means
for varying includes fore and aft tanks partially filled with water
and a positive displacement pump operatively connected to transfer
water from one to the other of said tanks.
22. A buoy system in accordance with claim 1 including means for
reducing the buoyancy of said housing after its deployment in the
water.
23. A buoy system for deployment beneath the surface of a body of
flowing water, comprising,
a buoy having positive buoyancy,
an anchor disposed on the bottom of the body of water, and
a flexible cable having a length substantially greater than the
depth of said body of water interconnecting said buoy and said
anchor,
said buoy including a pressure sensitive instrument for generating
a signal indicative of the depth of said buoy beneath the
surface,
said buoy also including means responsive to said signal for
varying the weight distribution of said buoy, the attitude of said
buoy, and lift due to the flow of water over the surface of said
buoy, whereby the depth of said buoy is varied.
24. A buoy system in accordance with claim 23 in which said means
for varying includes fore and aft tanks partially filled with water
and a pump for transferring water between said tanks.
Description
FIELD OF THE INVENTION
This invention relates generally to buoys which are deployed in the
ocean and which contain or to which are attached equipment for
detecting various phenomena and particularly to sonobuoys equipped
to detect underwater sounds.
BACKGROUND OF THE INVENTION
Typically a sonobuoy is deployed at a known position in the ocean
and is held there, at or near the surface, by a long cable
connected to an anchor resting on the bottom. One or more sound
sensitive devices are supported, either on the anchor cable or by a
separate support, to generate signals in response to incident
acoustic energy. Instead of being transmitted continuously, such
signals are usually stored by a suitable recorder in the sonobuoy
and transmitted from time to time to a surface vessel or to a
hovering aircraft. Transmission is usually by means of a radio link
and accordingly it is necessary that the sonobuoy, or at least part
of it, be above the surface of the sea during transmission.
Various sonobuoy mooring systems have been proposed. In one
arrangement, the entire sonobuoy floats on the surface at all
times, held by a long slack cable fastened to an anchor. This
arrangement requires that the sonobuoy package and the cable be
sturdy enough to withstand the constant buffeting by surface waves,
winds and currents. Additionally, the buoy, being on the surface is
subject to ready detection by hostile forces.
In another arrangement, the sonobuoy is held well below the surface
by a taut anchor cable. A small surface float, carrying an antenna
and perhaps other equipment, is tethered to the main buoy by a
slack cable. This arrangement requires substantial positive
buoyancy, a strong cable, and a heavy anchor. Although the surface
float may be smaller than the sonobuoy, nevertheless it is on the
surface and subject to damage and/or detection.
It is a general object of the present invention to provide an
improved sonobuoy system.
Another object is to provide a sonobuoy which remains entirely
below the surface except during periods of data transmission.
Another object is to provide a sonobuoy which is never exposed to
excessively rough sea surfaces.
Another object is to provide a sonobuoy which will seek and
maintain any commanded depth beneath the surface.
Another object is to provide an arrangement by which the depth of
the sonobuoy can be varied from time to time or continuously by a
predetermined program or by command.
A more specific object is to provide a sonobuoy the depth of which
can be varied by utilizing the power contained in ocean
currents.
SUMMARY OF THE INVENTION
In a recent examination of ocean current distribution, it was found
that virtually nowhere in the first 1,000 feet of ocean surface
water does the current drop below 0.05 knots, except during tide
switching in shelf waters which is only for half an hour or so. The
present invention is based on the principle of utilizing, rather
than resisting, such currents. In a preferred embodiment, the buoy
is tethered by a slack moor. Its depth beneath the surface is
measured by a suitable sensor such as a pressure sensitive device
which controls a mechanism for adjusting the attitude of the buoy
itself and/or vanes attached thereto thereby varying the lifting
forces exerted and the depth of the buoy. The depth may be
maintained at a predetermined fixed level, or varied in accordance
with a program, or varied in response to a command.
BRIEF DESCRIPTION OF THE DRAWING
For a clearer understanding of the invention, reference may be made
to the following detailed description and the accompanying drawing,
in which:
FIG. 1 is a schematic elevation view of the buoy just after it has
been deployed;
FIG. 2 is a schematic plan view of the buoy;
FIG. 3 is a schematic cross section view taken on the line 3--3 of
FIG. 2;
FIG. 4 is a schematic cross section view taken on the line 4--4 of
FIG. 2;
FIG. 5 is a schematic elevation view showing how the buoy is held
by the slack moor in the presense of ocean currents;
FIG. 6 is a fragmentary schematic elevation view showing the buoy
on the surface during transmission with an antenna on top of an
inflated bag;
FIG. 7 is a schematic elevation view showing how the cable may be
kept off the ocean floor in the absence of ocean currents;
FIG. 8 is a partial cross section view of the buoy showing the
buoyancy and attitude adjusting equipment;
FIG. 9 is a schematic diagram of the initial buoyancy control
circuit;
FIG. 10 is a schematic block diagram of the depth control
equipment; and
FIG. 11 is a schematic block diagram of a portion of the equipment
shown in FIG. 10.
DESCRIPTION OF PREFERRED EMBODIMENT
Referring first to FIG. 1 a sonobuoy incorporating the invention is
indicated generally by the reference character 21 and includes a
housing 22. This figure is not drawn to scale and the invention may
be used with many of the standard sonobuoy packages, one of which
is about 60 inches long and 7 inches in diameter. The buoy 21 is
shown a short time after depolyment by a ship or by an aircraft.
Since it initially has a large positive buoyancy, it is, at this
time, at or near the surface 23 of the sea. Before being deployed,
it had attached thereto an appendage indicated generally by the
reference character 24 and shown in dotted lines in the position as
occupied before deployment. More specifically, the appendage 24
includes a sensor package 25, a cable metering and lock up package
26, a cable storage package 27, a floatation package 28 and a
combined power supply and anchor package 29.
When the sonobuoy is first dropped into the water, it will, in all
probability, sink beneath the surface momentarily but since it has
substantial positive buoyancy it will soon rise to the surface. The
appendage disconnects itself and starts falling to the bottom. The
sensor package 25 falls away exposing a plurality of acoustic
sensing devices such as the hydrophones 31 fastened to or suspended
from a cable 32. This cable includes conductors for carrying power
and signal currents and is fastened to the housing 22 by means of a
bridle 33 which, in turn, is fastened near opposite ends of the
sonobuoy 21. Since the buoy is floating, the descent of the
appendage 24 causes the cable 32 to pay out until the appendage
reaches the bottom. Then the drifting of the buoy 21 pulls
additional cable from the storage package 27 and through the lock
up package 26. It is preferred that the total length of the cable
be about 30 percent greater than the depth of the water at the
point of deployment. This can be accomplished simply by
predetermining the length of the cable or by adjusting the metering
and lock up package 24 for a length of cable appropriate to the
depth at which the buoy is to be deployed. Alternatively, a more
complex arrangement by which an additional 30 percent of cable is
payed out after the package hits the bottom may be used but such
apparatus has not been shown because it is within the skill of
those familiar with the art and is not part of the present
invention. The important thing for present purposes is that there
be sufficient cable to constitute a slack moor, that is, that the
cable extending from the anchor to the buoy 21 have a substantial
horizontal component as shown in FIG. 5.
As shown in FIGS. 1, 2, and 3, the buoy 21 is provided with vanes
36 and 37 fastened about amidships of the housing 22 near the top
as shown. These vanes are to provide a lift in addition to that
provided by the surface of the housing 22. Preferably they are
curved in shape so that, before deployment, they fold flush against
the cylindrical surface of the housing 22 but are extended as shown
after deployment. Such extension may be done manually or
automatically. The important thing is that they be so extended
after the buoy is deployed.
As shown in FIGS. 1, 2, and 4, an additional pair of vanes 38 and
39 is disposed on the housing 22 near the stern and positioned as
shown to prevent alternate vortex shedding, thereby eliminating
oscillations in the horizontal plane as the water currents pass
over the buoy 21. These vanes are also preferably curved to conform
to housing 22 to simplify storage and handling before
deployment.
On the top of the buoy 21 at about the central portion there is a
conforming rubber skin or bag 41 in the middle of which is mounted
an antenna 42. When the buoy is beneath the surface, the bag 41
lies close against the surface of the housing 22 and the antenna 42
is disposed horizontally as nearly flush as may be with the top
surface of the housing 22. When the buoy is brought to the surface
for the transmission of data, as will be more fully discussed, the
bag 41 is inflated thereby erecting the antenna 42, as shown in
FIG. 6. A conductor 43 connects the antenna with the interior of
the sonobuoy 21.
If the buoy 21 is to be deployed in regions where slack water is
likely to occur, some precautions should be taken to keep the cable
off the bottom of the ocean so that it does not become tangled with
anything should the buoy drift to a position nearly above the
anchor. As shown in FIG. 7, this may be done by making a portion of
the cable 45 which is near the anchor of a buoyant material or by
attaching floats to such a portion. This end may be accomplished
either by making the cable buoyant in the first place or by storing
floats in the package 28 and attaching them to the cable as the
last portion is payed out.
Referring to FIG. 8, there are shown schematicaaly two walls 48 and
49 which form, along with the housing 22, fore and aft tanks 51 and
52, respectively. A bidirectional positive displacement pump 53 is
mechanically connected to two electric motors 54 and 55. The motor
54 is used to establish initial buoyancy conditions while the motor
55 is used to vary the attitude of the buoy. It would of course be
possible to use a single motor for both purposes but it is
preferred, at present, to use two motors, as shown.
One side of the pump 53 is connected by means of a conduit 57
directly to the interior of the tank 51 while the opposite side is
connected by means of a conduit 58 to one side of a valve 59,
operated by a solenoid 61. The other side of the valve 59 is
connected by means of a conduit 62 to the interior of the tank 52.
The conduit 58 communicates with a conduit 63 which in turn
communicates with one side of a valve 64, operated by a solenoid
65. The other side of the valve 64 is connected to a conduit 66
which passes through the housing 22 and communicates with the open
sea. The conduit 57 communicates with a conduit 67 which is
connected to one side of a valve 68, operated by a solenoid 69. The
other side of the valve 68 is connected by means of a conduit 71 to
the inlet side of a check valve 72, the outlet side of which is
connected by means of a conduit 73 to the conduit 62. The check
valve 72 will pass fluid only in the direction shown, that is from
the conduit 71 to the conduit 73 but not in the other direction.
The valve 59 is open while the valves 64 and 68 are closed in the
absence of energization of their respective solenoids. Energization
of the solenoids closes valve 59 and opens valves 64 and 68.
Also shown in FIG. 8 is a pressure sensor 76 which communicates
with the open sea by means of a conduit 77 which extends through
the housing 22. The sensor 76 generates a signal, such as an
electric voltage or current or a mechanical displacement, which is
indicative of the pressure incident on the housing 22 which in turn
is indicative of the depth of the buoy. Additional control
equipment, to be more fully described, is shown in block diagram
form at 77. The equipment for processing and transmitting the
signal from the hydrophone 31 is shown in block diagram form at
78.
When the sonobuoy 21 is first deployed in the water, it has a very
substantial positive buoyancy and floats on the surface. After all
of the cable has been payed out, it is preferred that the buoyancy
be substantially decreased so that it is just slightly buoyant
during normal submerged operation. This is accomplished by means of
the valving apparatus just described above in connection with FIG.
8 and in connection with the circuitry of FIG. 9. Operation of this
equipment starts after the sonobuoy section 24 reaches the bottom
and all the extra cable is payed out. At that time, the power
supply within the package 29 is activated. This power supply may be
a radioisotope thermoelectric generator or a battery or other kind
of power source and is preferably converted from a low voltage to a
high voltage direct current for more efficient power transmission
up the cable to the sonobuoy 21 where it is reconverted to a low
voltage unidirectional current.
Referring now to FIG. 9, prior to the time the power supply is made
active there is no voltage in the circuit and the solenoids 61, 65
and 69 are de-energized with the result that the corresponding
valves 64 and 68 are closed while the valve 59 is open. When all of
the cable is payed out, the power supply is made active and a
voltage appears on conductors 81 and 82. A timing circuit 83 is
connected to these conductors and operates, when energized, to put
a voltage across a winding 84 for a predetermined time starting
immediately. The winding 84 is the operating winding of a relay
indicated generally by the reference character 85 and which
includes switches 86 and 87. When the winding 84 is energized, the
switch 87 closes, energizing solenoids 61, 65 and 69, thereby
closing valve 59 and opening valves 64 and 68. One terminal of the
motor 54 is permanently connected to the ground conductor 82 and
closure of switch 87 energizes the motor to run in such a direction
as to cause the pump 53 to pump fluid to the right as viewed in
FIG. 8. Thus, fluid is drawn through the valve 64, the conduits 63
and 58, the pump and the conduit 57 to the tank 51 and also to the
conduit 67, valve 68, valve 72 and conduit 62 to the tank 52. Since
the pump is a positive displacement pump, operation for a
predetermined time puts a predetermined quantity of fluid into the
tanks 51 and 52 which is divided approximately equally between
them. This quantity is so predetermined as to give the proper
buoyancy to the buoy 21 which is a slight positive buoyancy
sufficient to cause the buoy to tend to rise in the absence of
water current drag exerted on the cable 32. At the end of the
predetermined time, the winding 84 is de-energized, thereby
shutting off the motor 54, and de-energizing the winding 61, 65 and
69 so as to close the valves 64 and 68 and open the valve 59. The
result of this is that the pump 53 is now connected so that it can
now pump fluid back and forth between the tanks 51 and 52.
Referring now to FIG. 10 there is shown in block diagram form the
equipment which, in conjunction with that previously described,
controls the depth of the sonobuoy 21. A programmer 94 includes a
clock and generates signal voltages indicative of the desired depth
of the sonobuoy at various times in accordance with a predetermined
time schedule. For example, it may be desired that it stay below
the surface at a certain depth for 23 hours of the day and then
rise for 1 hour. The voltage from the programmer 94 is compared
with that of the depth sensor 76 in a comparison circuit 95 which
generates an error signal which is passed to a motor control
circuit 96 which controls the motor 55 to actuate the pump 53 so as
to pump fluid between the tanks 51 and 52 in the proper direction
to change the weight distribution of the buoy and consequently its
attitude and the angle of attack of the ocean currents thereby
causing the buoy to rise or descend as directed by the error
signal. It is preferred that the magnitude of the change in
attitude be correlated with the magnitude of the error signal so
that a command to change depth by small amount causes less change
in attitude than a command to change depth by a large amount. To
accomplish this, a signal indicative of the number of revolutions
of the pump 53 is fed back to the circuit 96 where it is compared
with the error signal from the comparison circuit 95. Such feedback
could, of course, be electrical but at present is is preferred to
use a simple mechanical converter including appropriate gearing,
all as shown schematically by the dotted line 97. Any of various
comparison and balancing circuits may be used, that preferred at
present being shown schematically in FIG. 11.
Referring now to FIG. 11, The error signal from the comparison
circuit 95 is applied through a summing resistor 101 to a junction
102. A potentiometer 103 having a grounded center tap has its
opposite extremities connected to voltage sources of opposite
polarity. Its wiper 104 is positioned by the mechanical connection
97 and is electrically connected through a summing resistor 105 to
the junction 102. The voltage of the junction 102 is the input to a
servo amplifier of conventional construction, the output of which
controls the motor 55.
The apparatus is designed so that when the buoy is at the desired
depth, the error signal from circuit 95 is zero and the wiper 104
in the center position shown. If the buoy is then commanded to
change depth, an error signal from circuit 95 places a voltage on
junction 102 which, through amplifier 106 and motor 55 causes the
pump 53 to rotate. The feedback path 97 adjusts the wiper 104 until
the voltage balances the error signal, whereupon the voltage of
junction 102 falls to zero and the pump stops. As the buoy
approaches the desired depth, the error signal from circuit 95
decreases, placing a voltage on junction 102 which drives the pump
in the opposite direction proportionally reducing buoy vertical
travel velocity until the buoy reaches the commanded depth.
It is to be noted that operation of either motor 54 or motor 55
adjusts the wiper 104. Therefore, the apparatus is designed and the
initial conditions established so that after the motor 54 has
concluded its pumping operation to establish the initial buoyancy
conditions, as previously explained, the wiper 104 is centrally
located, as shown. Therefore, before deployment of the buoy, the
wiper 104 is positioned away from the center by an amount
indicative of the number of revolutions of the pump 53 necessary to
pump the predetermined quantity of water into the tanks 51 and 52.
Since the pump 53 is a constant displacement pump, the quantity of
water pumped is directly related to number of revolutions which in
turn is directly related to the time of operation. Accordingly, it
is necessary to correlate, in the design, the parameters of the
pump 53, motors 54 and 55, the timer 83 and the initial offset of
the wiper 104.
Let us assume that the buoy 21 has been at its programmed depth
gathering information for a programmed time, for example, 23 hours,
and that it is to be brought to the surface so as to transmit the
information. The programmer 94 generates a suitable signal which
operates through the circuits and other equipment just described to
increase the lift and cause the buoy 21 to ascend. As it reaches a
predetermined depth, near the surface, as measured by the sensor
76, the programmer 94 operates a control valve 108 so as to open,
for a predetermined time, a passage from a tank 109 containing a
gas under pressure to the inflatable bag 41 which adds further
buoyancy, erects the antenna 42, and holds the antenna above the
waves after the buoy has surfaced. At the end of another
predetermined time, the programmer 94 operates the valve 97 so as
to vent the gas from the bag 41 to the atmosphere. The programmer
than generates another signal commanding the buoy to descend to its
previous depth, or, for that matter, to a different depth.
Also shown in FIG. 10 is an acoustic receiver 111 which may receive
sonic signals and override the programmer 94 should it, at any
time, be desired to bring the sonobuoy to the surface. This
receiver may, for example, by a part of a commercially available
acoustic command system, one suitable kind being that marketed by
AMF, Alexandria Division, Alexandria, Va, and designated model
200.
Waves at the surface of the sea cause an orbital circulation of the
underlying water. Such motion, although greatest near the surface,
extends a considerable distance below. As the waves increase in
size, the actual motion and the accompanying accelerations likewise
increase and extend further beneath the surface. This phenomenon is
utilized to prevent a programmed surfacing of the buoy if the sea
is so rough as to prevent reliable transmission of data and/or
endanger the buoy. An accelerometer 112 is provided which senses
the vertical acceleration of the orbital motion to which the buoy
is subjected as it approaches the surface. If such acceleration
exceeds a predetermined threshold, a signal is sent to the
programmer 94 directing it to override the programmed surfacing and
to command the buoy to descend.
From the foregoing it will be apparent that applicant has provided
a novel system which enables the sonobuoy to be disposed beneath
the surface of the sea for the majority of the time where it is not
subject to buffeting by waves and is not subject to ready detection
by the enemy. The sonobuoy can be programmed to go to any desired
depth by utilizing the free energy of ocean currents and to stay
there for any desired length of time consuming negligible electric
power. During this time the hydrophones can transmit their signals
to the signal equipment 78 which, for example, may include a tape
recorder and play back equipment as well as necessary radio
transmitters all as is well known to those skilled in the art. When
the sonobuoy comes to the surface, the recorder is played back and
the information transmitted to a nearby surface ship or hovering
aircraft. The details of the storage and transmission of the data
from the hydrophones however, are not a part of Applicant's
invention and are well knwon to those skilled in the art.
Although a specific example incorporating the Applicant's invention
has been described in considerable detail for illustrative
purposes, many modifications will occur to those skilled in the
art. It is therefore desired that the protection afforded by
Letters Patent be limited only by the true scope of the appended
claims.
* * * * *