Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
AUTO-ADJUSTABLE BUOYANCY PRESSURE VESSEL FOR SCUBA
[0001] Technical Field
[0002] This invention relates to the field of underwater diving, and
specifically to breathing apparatuses
and methods the facilitate control of depth and buoyancy of the diver.
[0003] Background of the invention:
[0004] The SCUBA diving industry had made significant technical progress in
most areas. The common
SCUBA system, however, is still very heavy and cumbersome to maneuver. Modern
materials, especially
composites, fiberglass and polymer-based materials can function as well as or
better than steel or
aluminum to contain the breathing gas mixture pressure at a much lighter
weight. However, simply using
lighter materials does not solve the problem because it only deals with one of
the forces operating on a
submerged object:
[0005] Gravity facilitates the downward force operating on a SCUBA tank. The
total mass of the SCUBA
at any given point in time is composed of:
(a) Its construction-related mass: a tank made of steel or aluminum is usually
heavier than a tank made of
lighter material such as composites, carbon fiber, etc.
(b) The density of the breathing gas mixture. The denser the gas, the heavier
it is.
[0006] The upward force operating on a SCUBA tank is a function of its volume:
Archimedes' principle
states that the upward buoyant force that is exerted on a body immersed in a
fluid is equal to the weight
of the fluid that the body displaces. Since common SCUBA tanks have fixed
volume, they displace a fixed
amount of water and the upward force is constant. FIG. 1 provides an
illustration of these forces.
[0007] Two of the three components influencing the tank vertical position
while submerged remain
constant through the dive: its construction related mass and its total volume.
The third component is the
total mass of the breathing gas. As the diver consumes the breathing gas
throughout the dive, the
pressure inside the SCUBA tank is reduced and with it the density of the
breathing gas. For this reason,
common scuba tanks (12L at 200 BAR) are roughly 3 kg heavier at the beginning
of the dive than at its
end (12L at 50 BAR). As a result, SCUBA divers take additional weight with
them to maintain buoyancy
towards the end of the dive.
[0008] New materials allow for a weight reduction of between two thirds and a
half of the conventional
SCUBA tank. The caveat is that the same SCUBA tank will be buoyant by a force
roughly equal to this
weight reduction. That, in turn, means that the diver has to carry the
additional weight anyway to
maintain neutral tank buoyancy, which defeats the purpose of building the
SCUBA tank from lighter
materials.
[0009] Disclosure of Invention
[0010] The present invention provides methods of constructing and using a
lightweight SCUBA tank with
a dynamic buoyancy feature, allowing it to decrease its volume when needed.
This feature can also be
used to vary the tank buoyancy at any point along the dive thereby reducing or
even eliminating the need
RECTIFIED SHEET1RULE 91) - ISA/US
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
for the standard buoyancy system (i.e. a buoyancy compensation device and
weight system). Combined,
the total reduction of mass the diver needs to carry can be as much as 70%.
Such a decrease in load
quickly translates into many aspects of the SCUBA industry:
(1) The ability to bring a larger percentage of the population into the sport,
especially these sectors of the
population that finds the weight of the equipment to be a barrier.
(2) The ability to simplify the art of SCUBA diving buoyancy.
(3) Reduced energy costs in diving operations that carry SCUBA tanks and other
equipment (trucks, boats,
etc.)
(4) Increasing the safety of both recreational divers and diving
professionals.
[0011] Brief Description of the Drawings
[0012] FIG. 1 is an illustration of the forces affecting an object's buoyancy
while submerged.
[0013] FIG. 2 provides schematic illustrations of variable volume tanks in
accord with the present
invention.
[0014] FIG. 3 is a schematic illustration of a controlled variable volume tank
according to the present
invention.
[0015] Modes of Carrying Out the Invention and Industrial Applicability
[0016] Description of the invention: A pressure vessel for SCUBA that allows
manual and automatic
buoyancy control.
[0017] A variable volume SCUBA tank can be achieved by applying design
principles as described herein.
FIG. 2 shows two examples for the lightweight variable volume SCUBA tank.
Other examples are disclosed
in PCT/U52017/034896, filed 28 May 2017, which is incorporated herein by
reference.
[0018] The working principle of the variable volume tank is that the buoyancy
of the pressure vessel can
be changed by delivering fluid into or out of the fluid chamber. The mass of
the pressure vessel itself and
its components remains constant, the only change is in the volume of the gas
chamber, which affects the
buoyancy of the pressure vessel. For this invention, the fluid can be
seawater, fresh water or whatever
fluid medium the SCUBA diver is submersed in.
[0019] A diving system provided by this invention can comprise the following
elements:
(1) A pressure vessel that contains a chamber for the gas breathing mixture
and a separate chamber for
the fluid. The chambers are separated such that the contents of the two
chambers cannot come in
contact with one another. The separation is moveable such that the volume of
either compartment can
be made larger or smaller at the expense of the other.
(2) A gas valve, mounted to the gas compartment of the pressure vessel, so
that air can be filled and used
by the diver.
(3) A purge valve, allowing liquid to be removed from the fluid chamber.
(4) A fluid delivery system comprised of a pump which is coupled to an energy
source and a control
system. The drive for the pump can be pneumatic or electronic. Some pumps can
be used to both fill and
2
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
empty the fluid compartment by reversing the direction of the pump. This can
be a preferred setup for
the diving system described here because it can reduce the overall weight and
number of components. A
standard pump and separate fluid purge valve for the fluid compartment can
provide an acceptable
variation.
(5) A control, e.g., remote control, that communicates with the control system
of the pump. The control
system can comprise direct control of the pump, e.g., buttons or switches that
allow the diver to directly
control direction of fluid flow, rate of fluid flow (which includes both
zero/max and variable rate
embodiments), or combinations thereof, of the pump; and can also comprise more
automated control
systems such as programmable or special purpose computers, logic controllers,
analog electronic circuits,
ASICs, or other control systems known in the art and suitable for controlling
the operation of a pump or
similar fluid transfer device responsive to diver inputs and sensors
(according to the needs of the
particular embodiment).
(6) In some embodiments, the control system is able to receive and be
programmable to respond to the
diver's depth gauge. In some embodiments, the system can be equipped with a
depth gauge separate
from that of the diver. In some embodiments the system can be equipped with an
inertial measurement
unit so that vertical speed can be monitored either in combination with or
instead of a depth gauge.
Other sensors capable of indicating depth or rate of change in depth can also
be used.
[0020] In some embodiments, the control system is able to receive and be
programmable to respond to
the diver's physiological parameters such as breathing patterns, heart rate,
muscular or brain activity,
blood chemistry, or other indications of physiological state. In some
embodiments the system can be
equipped with air-pressure or air-flow monitoring devices and a physiological
sensing system such as a
heart rate monitor.
[0021] An example system configuration is illustrated in FIG. 3, and described
below. The example
embodiment provides a variable volume pressure vessel with electrical
controls. It comprises a bi-
directional pump that allows the pump to be used to communicate fluid into or
out of the pressure
vessel, using the motor directly to switch between the two modes. It can also
use multiple pumps, or a
unidirectional pump with a controlled fluid release valve to remove fluid from
the pressure vessel.
[0022] System operation:
[0023] The amount of liquid introduced into the pressure vessel is controlled
such that the total
buoyancy of the diver and its equipment is one of the following:
(1) Positive ¨ meaning that the buoyancy of the diver and its equipment is
greater than their combined
weight. This will place an upward force on the diver towards the water
surface.
(2) Neutral ¨ meaning that the buoyancy of the diver and its equipment is
equal to their combined
weight. This will place a net zero force on the diver in terms of upward or
downward movement.
(3) Negative ¨ meaning that the buoyancy of the diver and its equipment is
less than their combined
3
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
weight. This will place a downward force on the diver away from the water
surface and towards the
bottom.
[0024] The three types of buoyancy described above can be tailored to the need
of the diver in any stage
of the dive. Incorporating in the system a pressure gauge to detect the depth
of the pressure vessel and
having the pressure gauge and/or inertial measurement unit communicate with
the controls of the
element that introduce fluids into the pressure vessel can allow automatic
control of the system's
buoyancy. Such a system allows the diver to reduce or even eliminate the need
for a weight system and
the common buoyancy compensating device (BCD) that is standard today. Examples
include:
[0025] Descending and the automatically controlled negative buoyancy function:
[0026] A diver fitted with a system such as those described herein and common
SCUBA gear but without
weights and BCD enters the water. The pump of the pressure vessel is
configured such that it can fill or
empty the tank as needed. An electric remote control allows the diver to
control the speed of the pump
in each direction and thereby the rate at which the pressure vessel changes
its buoyancy. The motor of
the pump is connected to a controls circuit which allows the pump to respond
to various signals in a
predetermined manner. The pressure vessel system is also equipped with a
pressure gauge sensor that
can detect the ambient pressure while submerged. The pressure gauge is used to
detect depth and is in
communication with the controls board that operates the motor. See FIG. 3. The
diver can control the
system by direct control of the speed of the pump, or the speed of the pump
can be controlled
responsive to other input from the diver, e.g., an indication of rate of
ascent or descent desired, or an
indication to ascend or descend faster or slower than the current pace, or
other diver input that can be
correlated with a pump speed required to accomplish the diver's objective.
[0027] When the diver enters the water its total buoyancy (meaning diver and
gear together) is positive
and the diver floats. Once the diver wishes to descend the diver can activate
the pump so that fluid is
directed into the pressure vessel. The pressure vessel then becomes negatively
buoyant until the diver
begins to descend. If the diver chooses to not make any changes to the system,
the diver rate of
descending will accelerate because the diver's wetsuit and any other
compressible gear will be reduced
proportionally to the ambient pressure.
[0028] Alternatively, the diver can choose to descend in a controlled manner.
For example, the diver can
choose a descending rate of 2 feet per second. An automatically controlled
descending rate can be
desirable for divers that need more time to equalize anatomical cavities such
as ears and sinuses. Another
reason that controlled descent is desirable is when descending into blue water
without a reference point
such as a wall or the sea floor, divers find themselves rapidly descending and
can easily exceed the safety
limits of the intended dive plan. The pump's motor control can be in
communication with the depth
gauge of the system to allow the diver to set a specific descent rate. As soon
as the diver begins
descending, the controls can change the direction of the pump and remove water
from the pressure
vessel such that the buoyancy remains negative enough for the diver to
maintain a 2 feet per second
4
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
descent rate. If the depth gauge transmits a signal indicating too slow of a
descent rate, the pump can
add water to the tank.
[0029] Gaining, regaining and maintaining perfect buoyancy and the
automatically controlled perfect
buoyancy function:
[0030] Once the diver reaches a depth where they would like to suspend
themselves at a certain depth,
the diver can use the controls to fill or empty the pressure vessel as needed
until the diver reaches a state
of perfect buoyancy.
[0031] Alternatively, the diver can choose to set a specific depth in which
the diver wishes to remain
suspended using the remote control. The controls board can use the input from
the depth gauge to direct
the motor and thereby the pump to maintain the diver's position by filling and
emptying the pressure
vessel as needed. For example, as the diver breathes in and out underwater,
the change in the diver's
lung volume plays a role in maintaining perfect buoyancy. The system's
controls can be configured such
that the system automatically compensates for these minor volume changes and
maintains the diver at a
specific depth range.
[0032] When the diver wishes to change into a new depth, the automatic perfect-
buoyancy function can
be turned off and the diver can swim and ascend or descend using the pressure
vessel buoyancy system.
Once the diver reaches a new depth destination, the process described herein
can resume.
[0033] The diver can choose to allow the system to automatically establish
neutral buoyancy at any
depth the diver is in, or depth indicated by the diver. The control board can
use the input from an inertial
measurement unit to direct the pump motor and thereby the pump to maintain a
state of minimal
vertical movement. For example, a diver may swim up or down and then stop
swimming at the desired
depth. The system can be configured such that it automatically limits vertical
movement to a very narrow
range. Automatically in this context doesn't necessarily mean instantaneously.
The system can 'catch-up'
to the diver until vertical movement is reduced to within the programmable
range.
[0034] Ascending and automatically controlled positive buoyancy function:
[0035] One of the key elements of SCUBA is a controlled ascent to the surface.
Because of the pressure
decrease during the ascent, divers who ascend too quickly increase their
potential exposure to
decompression sickness. Lung expansion because of uncontrolled ascent is also
a serious risk in SCUBA
diving. Using the system described in this invention, the diver can set an
ascent rate well within the
recommended safety guidelines of 30 ft/min.
[0036] The system can be configured so that the pump's motor controls are in
communication with the
depth gauge of the system. The diver can set a specific ascent rate using the
remote control, such that
the pump's motor control responds to the signal from the depth gauge. As soon
as the diver begins
ascending, the controls can direct the pump to add or remove fluid from the
pressure vessel such that
the buoyancy remains positive enough for the diver to maintain a 30 feet per
second ascent rate. If the
depth gauge transmits a signal indicating too fast of an ascent rate, the pump
can add water to the tank
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
which will reduce buoyancy and slow down the ascent. Another example is at the
recommended safety
stop: the diver can set a safety stop and the system control can adjust the
buoyancy to stop the ascent at
the safety stop.
[0037] The system can also be used to rescue divers. The system can control
buoyancy to implement an
ascent to the surface, e.g., a "fast as possible" emergency ascent, or a
"quick but safe" ascent, responsive
to an input or condition. As an example, in a system with a physiological
monitor the control system can
be configured to implement an automatic ascent when the physiological monitor
indicates a diver in a
distressed condition, e.g., a heart rate monitor indicates heart failure, or
breathing monitor indicates
troubled breathing, or a brain activity monitor indicates brain activity not
consistent with normal diving
(e.g., asleep, fainted, unconscious), or a motion monitor indicates diver
activity outside a predetermined
profile for this dive. The control system can allow a diver to override the
automatic ascent, which can be
useful, as an example, if the physiological monitor experiences a fault that
would cause an undesired
automatic ascent.
[0038] The system can also be used to enforce territorial or depth
limitations. As an example, the control
system can be configured to maintain buoyancy such that an inexperienced diver
cannot descend past a
predetermined safe depth, or such that a diver cannot descend past a
predetermined depth when lower
depths are environmentally fragile. As another example, the control system can
be configured to
maintain buoyancy based on the location of the diver, e.g., to maintain the
diver at a safe distance above
dangerous bottom conditions, or conditions where the bottom is environmentally
fragile, but allow
greater depths when away from the area of such conditions. As another example,
the control system can
be configured to respond to a signal that the diver has left a predetermined
dive area, and implement a
controlled ascent so that the diver cannot stay underwater outside the
predetermined dive area.
[0039] The system can also implement automatic ascents, or partial ascents,
responsive to other dive
conditions. For example, a diver can have a control input that must be
activated by the diver at
predetermined intervals of time, indicating that the diver is still
functioning and not in distress. If the
control input is not activated, the system can implement a controlled ascent,
to the surface or to some
predetermined depth at which second party evaluation or rescue is implemented.
As another example,
the control system can implement an automatic ascent responsive to
predetermined conditions, e.g., a
"recall" signal from another diver or the surface, a "low air" or "out of air"
signal from the breathing
apparatus, or a "lost" signal representative of a lost connection with a
necessary tool or safety device or
supervising diver.
[0040] Personalizing the buoyancy control system response
[0041] Most air-integrated SCUBA computers available today monitor the
breathing gas mixture
consumption in real time. Since each individual lung capacity and breathing
pattern differ so does their
buoyancy response. On average, an experienced and calm diver will have roughly
10-12 breathing cycles
in a minute and experience a difference of 2 liters in lung volume in the
breathing cycle (i.e. inhalation
6
CA 03109637 2021-02-12
WO 2020/041481 PCT/US2019/047519
and exhalation constitute one breathing cycle). The lung volume change
therefore causes a difference of
2 Kg or 4.4 lbs every 5-6 seconds approximately. An experience diver
constantly keeps in mind this
volume change and use it as fine buoyancy adjustments. However, when a diver
breathing pattern
changes both in depth and rate, the volume change can be up to 6 liters per
cycle which means a
buoyancy force change of 6kg or 13.2 lbs. This change can be a result of
swimming against a current, real
or perceived fear or any other reason.
[0042] The pump motor controls in some embodiments of the present invention
can be in
communication with an air-integrated computer, equipped with a learning
capability for the diver
average breathing pattern and able to detect increased breathing rates and
volumes. The data from the
computer can be used by the control system to adjust the rate at which the
fluid is introduced or
removed from the tank to better fit the needs of the diver at any given point
in time. It is worth noting
that the breathing cycle effect on buoyancy cancels itself out under normal
diving conditions. However,
as the breathing rate and volume increase, the cancellation effect can become
less pronounced.
[0043] For example, an experienced and calm diver begins the dive and the
control system detects that
the breathing pattern is normal. Accordingly, the control system makes no
adjustments to motor speed
and the diver buoyancy is controlled as described above. At some point in the
dive the diver enters a
thermocline and the water temperature drops by 10 degrees Celsius. The diver's
physiology needs to
catch-up to this sudden change of temperature and as part of the response the
rate and depth of
breathing increases sharply to 6 liters every 3 seconds. The air-integrated
computer detects the increased
air consumption within 20 seconds or 5 breathing cycles. The computer then
signals the controls board to
respond by increasing the fluid flow into and out of the pump so that the rate
of vertical movement of
the diver will better match the desired rate set by the diver.
[0044] Note that the above are just examples of how the buoyancy of the tank
and the diver can be
affected by operating the pressure vessel using the electrical controls. These
examples are not intended
to be all encompassing of the different uses of the described invention.
[0045] The present invention has been described in connection with various
example embodiments. It
will be understood that the above description is merely illustrative of the
applications of the principles of
the present invention, the scope of which is to be determined by the claims
viewed in light of the
specification. Other variants and modifications of the invention will be
apparent to those skilled in the art.
7
