U.S. patent application number 12/470279 was filed with the patent office on 2010-11-25 for buoyancy system for an underwater device and associated methods for operating the same.
Invention is credited to Matthew Ascari, Kenneth Blanchette, Sean Day, Robert Dietzen, Maria Fini, Matthew Gries, MATTHEW HERBEK, Braden Powell, John Rapp.
Application Number | 20100294192 12/470279 |
Document ID | / |
Family ID | 43123702 |
Filed Date | 2010-11-25 |
United States Patent
Application |
20100294192 |
Kind Code |
A1 |
HERBEK; MATTHEW ; et
al. |
November 25, 2010 |
BUOYANCY SYSTEM FOR AN UNDERWATER DEVICE AND ASSOCIATED METHODS FOR
OPERATING THE SAME
Abstract
A buoyancy system includes a chamber having a volume associated
therewith, and bladders within the volume of the chamber. Each
bladder contains a clathrate mixture in a liquid state. The chamber
includes an opening to allow surrounding water to circulate within
the volume and contact the bladders. As the chamber is submerged in
the surrounding water, the bladders expand based on the clathrate
mixture changing from the liquid state to a solid state. This
changes buoyancy by allowing less water to circulate within the
volume of the chamber.
Inventors: |
HERBEK; MATTHEW;
(Gainesville, VA) ; Dietzen; Robert; (Bealeton,
VA) ; Powell; Braden; (Lindon, UT) ;
Blanchette; Kenneth; (North Smithfield, RI) ; Day;
Sean; (Oak Hill, VA) ; Gries; Matthew;
(Houston, TX) ; Rapp; John; (Manassas, VA)
; Ascari; Matthew; (Manassas, VA) ; Fini;
Maria; (Manassas, VA) |
Correspondence
Address: |
MICHAEL W. TAYLOR
P.O. BOX 3791
ORLANDO
FL
32802-3791
US
|
Family ID: |
43123702 |
Appl. No.: |
12/470279 |
Filed: |
May 21, 2009 |
Current U.S.
Class: |
114/331 ;
114/332; 114/333 |
Current CPC
Class: |
B63G 8/24 20130101; B63G
8/14 20130101; B63G 2008/004 20130101; F28D 20/023 20130101; B63B
22/18 20130101 |
Class at
Publication: |
114/331 ;
114/332; 114/333 |
International
Class: |
B63G 8/14 20060101
B63G008/14; B63G 8/18 20060101 B63G008/18; B63G 8/22 20060101
B63G008/22 |
Claims
1. A buoyancy system comprising: a chamber having a volume
associated therewith; and a plurality of bladders within the volume
of said chamber, each bladder containing a clathrate mixture in a
liquid state; said chamber including at least one opening to allow
surrounding water to circulate within the volume and contact said
plurality of bladders, and as said chamber is submerged in the
surrounding water said plurality of bladders expand based on the
clathrate mixture changing from the liquid state to a solid state,
thereby changing buoyancy by allowing less water to circulate
within the volume of said chamber.
2. The buoyancy system according to claim 1, wherein the clathrate
mixture comprises water and a clathrating agent; and wherein the
clathrating agent comprises at least one of methane, floro-methane,
propane, floro-propane and hydrogen.
3. The buoyancy system according to claim 1, wherein each bladder
comprises a water-tight enclosure so that the clathrate mixture
therein does not directly contact the water.
4. The buoyancy system according to claim 1, wherein each bladder
comprises an elastic enclosure that expands as the clathrate
mixture changes to the solid state.
5. The buoyancy system according to claim 4, wherein the elastic
enclosure comprises a thermally conductive material.
6. The buoyancy system according to claim 1, wherein the clathrate
mixture comprises water and a clathrating agent, and each bladder
maintains a predetermined pressure on the clathrate mixture so that
the clathrating agent does not vaporize when the clathrate mixture
is in the liquid state.
7. The buoyancy system according to claim 1, further comprising a
water permeable enclosure surrounding said plurality of bladders
within the volume of said chamber.
8. The buoyancy system according to claim 1, wherein each bladder
is spherically shaped.
9. The buoyancy system according to claim 1, further comprising a
respective spacer coupled between adjacent bladders so that said
bladders are spaced apart from one another within the volume of
said chamber.
10. The buoyancy system according to claim 1, wherein said
plurality of bladders form a three-dimensional array of
bladders.
11. An underwater device comprising: a housing; and a buoyancy
system carried by said housing, and comprising a chamber having a
volume associated therewith, and a plurality of bladders within the
volume of said chamber, each bladder containing a clathrate mixture
in a liquid state, said chamber including at least one opening to
allow surrounding water to circulate within the volume and contact
said plurality of bladders, and as said chamber is submerged in the
surrounding water said plurality of bladders expand based on the
clathrate mixture changing from the liquid state to a solid state,
thereby changing buoyancy of the underwater device by allowing less
water to circulate within the volume of said chamber.
12. The underwater device according to claim 11, wherein the
clathrate mixture comprises water and a clathrating agent; and
wherein the clathrating agent comprises at least one of methane,
floro-methane, propane, floro-propane and hydrogen.
13. The underwater device according to claim 11, wherein each
bladder comprises a water-tight enclosure so that the clathrate
mixture therein does not directly contact the water.
14. The underwater device according to claim 11, wherein each
bladder comprises an elastic enclosure that expands as the
clathrate mixture changes to the solid state.
15. The underwater device according to claim 14, wherein the
elastic enclosure comprises a thermally conductive material.
16. The underwater device according to claim 11, wherein the
clathrate mixture comprises water and a clathrating agent, and each
bladder maintains a predetermined pressure on the clathrate mixture
so that the clathrating agent does not vaporize when the clathrate
mixture is in the liquid state.
17. The underwater device according to claim 11, further comprising
a water permeable enclosure surrounding said plurality of bladders
within the volume of said chamber.
18. The underwater device according to claim 11, wherein each
bladder is spherically shaped.
19. The underwater device according to claim 11, further comprising
a respective spacer coupled between adjacent bladders so that said
bladders are spaced apart from one another within the volume of
said chamber.
20. The underwater device according to claim 11, wherein said
housing and said buoyancy system are configured so that the
underwater device is an underwater glider.
21. The underwater device according to claim 11, wherein said
housing and said buoyancy system are configured so that the
underwater device is a sonar buoy.
22. A method for changing buoyancy of an underwater device
comprising a buoyancy system, the buoyancy system comprising a
chamber having a volume associated therewith, and includes at least
one opening to allow water to circulate within the volume, and a
plurality of bladders within the volume of the chamber, with each
bladder containing a clathrate mixture in a liquid state, the
method comprising: placing the underwater device in the water;
submerging the underwater device based on the surrounding water
entering the at least one opening within the chamber and contacting
the plurality of bladders; and expanding the plurality of bladders
based on the clathrate mixture changing from the liquid state to a
solid state so that less water is circulated within the volume of
the chamber, thereby changing the buoyancy of the underwater
device.
23. The method according to claim 22, further comprising
contracting the plurality of bladders after having been expanded,
the contracting based on the clathrate mixture changing from the
solid state back to the liquid state so that more water is
circulated within the volume of the chamber, thereby changing the
buoyancy of the underwater device.
24. The method according to claim 22, wherein the clathrate mixture
comprises water and a clathrating agent; and wherein the
clathrating agent comprises at least one of methane, floro-methane,
propane, floro-propane, and hydrogen.
25. The method according to claim 22, wherein each bladder
comprises a water-tight enclosure so that the clathrate mixture
therein does not directly contact the water.
26. The method according to claim 22, wherein each bladder
comprises an elastic enclosure that expands as the clathrate
changes to the solid state.
27. The method according to claim 26, wherein the elastic enclosure
comprises a thermally conductive material.
28. The method according to claim 22, wherein each bladder
maintains the clathrate mixture pressure above the vaporization
pressure of the clathrating agent.
29. The method according to claim 22, wherein the buoyancy system
further comprises a water permeable enclosure surrounding the
plurality of bladders within the volume of the chamber.
30. The method according to claim 22, wherein each bladder is
spherically shaped.
31. The method according to claim 22, wherein the buoyancy system
further comprises a respective spacer coupled between adjacent
bladders so that the bladders are spaced apart from one another
within the volume of the chamber.
32. The method according to claim 22, wherein the housing and the
buoyancy system are configured so that the underwater device is at
least one of an underwater glider and a sonar buoy.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of underwater
devices, and more particularly, to a buoyancy system for
controlling buoyancy of an underwater device.
BACKGROUND OF THE INVENTION
[0002] An underwater glider is a type of underwater device that
collects subsurface data in an observation region. The underwater
glider is typically a torpedo shaped, winged device that moves
through the water in a saw-tooth sampling pattern by changing its
buoyancy. The underwater glider is neutrally buoyant, and typically
includes a buoyancy system in its nose section.
[0003] The buoyancy system may be based on a displacement piston.
To diver the displacement piston moves water into nose section of
the underwater device. This makes the underwater glider's nose
heavy. To ascend, water is pushed out of the nose section by the
displacement piston. This makes the underwater glider's nose
lighter.
[0004] Even in view of the advances made in buoyancy systems, there
is still a need to improve such systems. For example, U.S. Pat. No.
6,131,531 discloses a selectively deformable buoyancy system. The
buoyancy system includes a housing having walls defining an
interior, sealable cavity. Changing the volume of the cavity
controls buoyancy. The cavity has an original volume when the walls
are maintained at or above a preselected temperature. The walls are
deformed at temperatures below the preselected temperature to
define a volume less than the original volume. The housing returns
to the original volume when the temperature of the walls is raised
above the preselected temperature.
[0005] Composite materials may be used as part of a buoyancy
system, as disclosed in U.S. Pat. No. 4,482,590. In particular,
implosion resistant macrospheres for use in buoyancy systems may be
fabricated from synthetic foams, preferably from synthetic
thermosetting polymeric resins. The implosion resistant
macrospheres are primarily used in buoyancy devices at sea depths
in excess of 4,500 feet.
SUMMARY OF THE INVENTION
[0006] In view of the foregoing background, it is therefore an
object of the present invention to provide an improved buoyancy
system for controlling buoyancy of an underwater device.
[0007] This and other objects, advantages and features in
accordance with the present invention are provided by a buoyancy
system comprising a chamber having a volume associated therewith,
and a plurality of bladders within the volume of the chamber. Each
bladder may contain a clathrate mixture in a liquid state. The
chamber may include at least one opening to allow surrounding water
to circulate within the volume. When the chamber is submerged in
increasingly frigid surrounding water, the plurality of bladders
may expand based on the clathrate mixture changing from the liquid
state to a solid state. This thereby increases buoyancy by allowing
less water to circulate within the volume of the chamber.
[0008] Similarly, when the chamber ascends in the increasingly warm
surrounding water, the plurality of bladders may contract based on
the clathrate mixture changing from the solid state to the liquid
state. This thereby decreases buoyancy by allowing more water to
circulate within the volume of the chamber.
[0009] Each bladder may comprise a water-tight enclosure so that
the clathrate mixture therein does not directly contact the water.
The clathrate mixture may comprise water and a clathrating agent.
Each bladder may maintain a predetermined pressure on the clathrate
mixture so that the clathrating agent does not vaporize when the
clathrate mixture is in the liquid state. Vaporization of the
clathrating agents would make an underwater device with such a
buoyancy system permanently buoyant. The maintained minimum
pressure thus depends on the clathrating agent, since each
clathrating agent has a unique dissolution pressure.
[0010] Each bladder may comprise an elastic enclosure that expands
as the clathrate mixture changes to the solid state. The elastic
enclosure may comprise a thermally conductive material. The
thermally conductive material advantageously allows the temperature
of the surrounding water to be efficiently transferred to the
clathrate mixture. As the water temperature cools, the clathrate
mixture decreases density when it begins to freeze. The clathrate
mixture expands as it freezes, similar to an ice cube that
floats.
[0011] Once the clathrate mixture reaches a depth in the water
where it can begin forming ice, each bladder expands as a result of
the volume increase of the ice. This volume increase, multiplied
for the total number of bladders, causes water to be forced out of
the chamber. This decreases the overall mass while displacing the
same volume of water. As a result, the buoyancy changes. The same
concept applies in reverse as the ice melts. The bladders will
shrink and the buoyancy system will weigh more as more water is
allowed to enter the chamber, and its buoyancy will change
again.
[0012] The buoyancy system may further comprise a respective spacer
coupled between adjacent bladders so that the bladders are spaced
apart from one another within the volume of the chamber. This
advantageously helps with the transfer of heat from the water to
the clathrate mixture since the water will surround each bladder,
as compared to partially surrounding the bladders when they are
bunched up against one another. Moreover, each bladder may be
spherically shaped to provide a greater surface area for the water
to contact, thereby improving heat transfer.
[0013] The bladders may form a three-dimensional array of bladders.
The buoyancy system may further comprise a water permeable
enclosure surrounding the plurality of bladders within the volume
of the chamber. The water permeable enclosure advantageously
prevents anyone of the bladders from escaping the chamber.
[0014] Another aspect of the present invention is directed to an
underwater device comprising a housing, and a buoyancy system
carried by the housing. The buoyancy system may be as defined
above. The housing and the buoyancy system may be configured so
that the underwater device is an underwater glider or a sonar buoy,
for example.
[0015] Yet another aspect of the present invention is directed to a
method for changing buoyancy of an underwater device comprising a
buoyancy system as described above. The method may comprise placing
the underwater device in the water, and submerging the underwater
device based on the surrounding water entering the at least one
opening within the chamber and contacting the plurality of
bladders. The method may further comprise expanding the plurality
of bladders based on the clathrate mixture changing from the liquid
state to a solid state so that less water is circulated within the
volume of the chamber, thereby changing the buoyancy of the
underwater device. The method may further comprise contracting the
plurality of bladders after having been expanded, with the
contracting being based on the clathrate mixture changing from the
solid state back to the liquid state so that more water is
circulated within the volume of the chamber, thereby changing the
buoyancy of the underwater device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic block diagram of an underwater glider
with a buoyancy system in accordance with the present
invention.
[0017] FIG. 2 is a schematic block diagram of a sonar buoy with a
buoyancy system in accordance with the present invention.
[0018] FIG. 3 is a block diagram of a buoyancy system, wherein each
bladder therein comprises a clathrate in a liquid state in
accordance with the present invention.
[0019] FIG. 4 is a block diagram of a buoyancy system, wherein each
bladder therein comprises a clathrate in a solid state in
accordance with the present invention.
[0020] FIG. 5 is a block diagram of a buoyancy system, wherein the
bladders therein form a three-dimensional array of bladders in
accordance with the present invention.
[0021] FIG. 6 is block diagram of a buoyancy system, wherein a
water permeable enclosure surrounds the bladders in accordance with
the present invention.
[0022] FIG. 7 is a flow chart for a method for changing buoyancy of
an underwater device in accordance with the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0024] Referring initially to FIG. 1, an underwater device 10
comprises a housing 12, and a buoyancy system 20 carried by the
housing. The underwater device 10 is illustrated as an autonomous
underwater glider that may be used to collect subsurface data in an
observation region. The underwater glider is neutrally buoyant, and
travels through the water in a saw-tooth-sampling pattern 22 by
using the buoyancy system 20 to change its buoyancy. Although the
underwater device 10 is illustrated as an autonomous underwater
glider, the buoyancy system 20 is readily applicable to other types
of underwater devices, such as a sonar buoy, for example, as
illustrated in FIG. 2.
[0025] As will be discussed in greater detail below, the buoyancy
system 20 changes buoyancy of the underwater device 10 based on the
use of a plurality of bladders 30, where each bladder contains a
clathrate mixture. The plurality of bladders 30 may also be
referred to as a blister pack. The clathrate mixture comprises
water and a clathrating agent, as will be discussed in greater
detail below.
[0026] The bladders 30 are in contact with the water, and expand or
contract based on the effects of the water's temperature on the
clathrate mixture. The expansion or contraction of the bladders 30
affects the buoyancy of the underwater device 10.
[0027] The clathrate mixture changes from a liquid state to a sold
state as the underwater device 10 submerges, and from the sold
state back to the liquid state as the underwater device 10 rises.
When the clathrate mixture is in the solid state, the mixture may
also be referred to as a clathrate hydrate. Transition between the
liquid and solid states is based on the temperature of the water
surrounding the bladders 30. The sharpness of the
saw-tooth-sampling pattern 22 depends on the rate of fusing the
clathrate hydrate (bottom saw-tooth-sampling pattern) and on the
rate of melting the clathrate hydrate (top saw-tooth-sampling
pattern).
[0028] Referring now to FIGS. 3 and 4, the buoyancy system 20
comprises a chamber 24 having a volume associated therewith, and
the bladders 30 are within the volume of the chamber. The chamber
24 includes an opening 40 facing the nose of the underwater device
10, and allows water to flow into the chamber 24 and contact the
bladders 30. The chamber 24 may further include another opening 42
facing the rear of the underwater device 10 so that the water exits
the chamber 24 as fresh water enters. Buoyancy of the underwater
device 10 is based on the amount of water within the chamber 22,
which is based on how much of the clathrate mixture within the
bladders 30 are in a liquid and/or solid state.
[0029] As readily appreciated by those skilled in the art, the
clathrate mixture comprises water and a clathrating agent. The
clathrating agent may include, but are not limited to, methane or
propane, for example. The clathrate agent is not limited to a
single type clathrating agent. The bladder 30 may include more than
one type of clathrating agent. When the clathrate is in the solid
state, the clathrate mixture is also referred to as a clathrate
hydrate. Clathrate hydrates are crystalline compounds defined by
the inclusion of a guest molecule within a hydrogen bonded water
lattice. Gas hydrates are a subset of clathrate hydrates wherein
the guest molecule is a gas at or near ambient temperatures and
pressures. Such gasses include methane, propane, carbon dioxide,
hydrogen, for example; although not all the gas hydrates are
suitable for buoyancy modulation when their solidified state is
denser than the liquid state (as is the case for carbon dioxide
hydrate).
[0030] The clathrate mixture changes density when it freezes. As
best illustrated in FIG. 3, the clathrate mixture is in a liquid
state so that the bladders 30 are at a normal size. The bladders 30
are separated from one another when the clathrate mixture is in the
liquid state. When the clathrate mixture freezes, the bladders 30
expand, as best illustrated in FIG. 4. Instead of being separated
from one another, the bladders 30 now are closer with one another
when in the solid state, possibly in contact with one another.
[0031] Each bladder 30 comprises a water-tight enclosure so that
the clathrate mixture therein does not directly contact the water.
The water-tight enclosure could be a variety of plastics or rubber
compounds that are elastic enough to accommodate the expanding
clathrate as it freezes, but rigid enough to prevent any leaks
between the ambient water and the clathrates.
[0032] Each bladder 30 maintains a predetermined pressure on the
clathrate mixture so that the clathrating agent does not vaporize
when the clathrate mixture is in the liquid state. For example, if
the clathrating agent is propane, then the bladder maintains a
pressure of at least 150 psi so that the propane does not vaporize
when the underwater device 10 is at the surface of the water.
Vaporization of the clathrating agent would make the underwater
device 10 permanently buoyant. The maintained minimum pressure thus
depends on the clathrating agent, since each clathrating agent has
a unique dissolution pressure.
[0033] As noted above, each bladder 30 comprises an elastic
enclosure that expands as the clathrate mixture changes to the
solid state. The elastic enclosure also comprises a thermally
conductive material. The thermally conductive material
advantageously allows the temperature of the water to be
efficiently transferred to the clathrate mixture. As the water
temperature cools, the clathrate mixture fuses into clathrate
hydrate which decreases in density as the mass expands. This is
similar to an ice cube that floats. As readily appreciated by those
skilled in the art, some clathrate hydrates become more dense than
their respective clathrate mixture states, and consequently, these
clathrating agents are not appropriate for use with a buoyancy
system 20. Once the clathrate mixture reaches a depth in the water
where it can begin forming ice, each bladder 30 expands as a result
of the volume increase of the ice.
[0034] When the clathrating agent is propane, for example, the
propane fuses with water at about 6 degrees Celsius. This volume
increase, multiplied for the total number of bladders 30, causes
water to be forced out of the chamber 24. This decreases the
overall mass while displacing the same change in volume of water.
As a result, the buoyancy increases. The same concept applies in
reverse as the clathrate hydrate melts. The bladders 30 will shrink
and the buoyancy system 20 will weigh more as more water is allowed
to enter the chamber 24, and its buoyancy will change again.
[0035] The size and number of bladders 30 within the chamber 24
will vary depending on the size or volume of the chamber, as well
as the intended application of the underwater device 10. There
needs to be enough bladders 30 to provide enough clathrate mixtures
within the chamber 24 to effect a density change in the underwater
device 10 to reverse its buoyancy. This would also depend on the
volume and weight of the underwater device 10, and the desired
climb or dive rates that may be required.
[0036] For illustrative purposes, the size of each bladder 30 may
be within a range of about 1/16 to 2 inches, for example. The size
of the chamber 24 is typically about 10 to 20% of the total volume
of the underwater device 10. For an underwater device 10 that is
about 25 cubic feet in volume, the chamber 24 would have a volume
of about 2.5 to 5 cubic feet. There needs to be a sufficient number
of bladders 20 to displace water from the chamber 24 so that there
is an effect on buoyancy of the underwater device 10.
[0037] The number of bladders 30 within the chamber 24 may also
compensate for failure of a certain number of bladders 30 that is
expected over time. Consequently, additional bladders 30 may be
included within the chamber 24 so that buoyancy can still be
controlled even with the loss of a portion of the bladders 30.
[0038] As illustrated in FIG. 3, the buoyancy system 20 may further
comprise a respective spacer 32 coupled between adjacent bladders
30 so that the bladders are spaced apart from one another within
the volume of the chamber 24. This advantageously helps with the
transfer of heat from the water to the clathrates since the water
will surround each bladder, as compared to partially surrounding
the bladders when they are bunched up against one another.
Moreover, each bladder 30 may be spherically shaped to provide a
greater surface area for the water to contact.
[0039] Referring now to FIG. 5, the bladders 30 may be coupled
together so that they form a three-dimensional array of bladders.
This resembles atomic crystal structures to maximize packing of the
bladders 30 within the chamber 24. The buoyancy system 20 may
further comprise a water permeable enclosure 50 surrounding the
plurality of bladders within the volume of the chamber, as
illustrated in FIG. 6. The water permeable enclosure 50
advantageously prevents anyone of the bladders from escaping the
chamber 24.
[0040] Another aspect of the invention is directed to a method for
changing buoyancy of an underwater device 10 comprising a buoyancy
system 20 as described above. Referring now to FIG. 7, from the
start (Block 70), the method comprises placing the underwater
device 10 in the water at Block 72. The water needs to have a
temperature at depth that is cold enough to freeze the clathrate
mixture within the bladders 30. The water needs to have a
temperature at the surface that is warm enough to melt the
clathrate mixture within the bladders 30. The underwater device 10
submerges and sinks from the surface based on the surrounding water
flooding the chamber 24 and engulfing the bladders 30 at Block
74.
[0041] The bladders 30 then expand at Block 76 as the clathrate
mixture changes from a liquid state to a solid state so that less
water is circulated within the volume of the chamber 24. This
increases the buoyancy of the underwater device 10. As a result,
the underwater device 10 floats toward the surface of the water at
Block 78. The bladders 30 contact warmer water causing the
clathrate mixture in the solid state to melt back into the liquid
state.
[0042] The cycle of descending and ascending is continuously
repeated in Blocks 74, 76 and 78. To end this cycle, the bladders
30 may rupture over time due to environmental causes at Block 80.
Similarly, the bladders 30 may fail when their elastic properties
become brittle over time at Block 82. Yet another option for ending
this cycle is to scuttle the underwater device 10 by rupturing the
bladders 30 on purpose at Block 84. The method ends at Block
86.
[0043] The blister pack approach has a significant lifecycle
advantage over a piston cylinder device or a single large bladder
device. Both these devices are disclosed in U.S. patent application
Ser. No. 12/017,966, which is incorporated herein by reference in
its entirety and is assigned to the current assignee of the present
invention.
[0044] In the illustrated buoyancy system 20, the failure of any
single bladder will have little effect on the overall performance
of a buoyancy cycle. It would take a large number of bladder
failures to terminate the buoyancy cycle. By eliminating single
points of failure, an underwater device 10 including a plurality of
bladders 30 will have a longer endurance. Its performance
eventually will gradually diminish as individual bladder failures
accumulate over time, as opposed to the catastrophic failure that
would occur with a piston cylinder device or with a large bladder
device. The blister pack bladder approach has a significant
production advantage over the piston cylinder device or the large
bladder device since the bladders 30 can be more easily mass
produced.
[0045] Many modifications and other embodiments of the invention
will come to the mind of one skilled in the art having the benefit
of the teachings presented in the foregoing descriptions and the
associated drawings. Therefore, it is understood that the invention
is not to be limited to the specific embodiments disclosed, and
that modifications and embodiments are intended to be included
within the scope of the appended claims.
* * * * *