U.S. patent number 3,877,425 [Application Number 04/832,675] was granted by the patent office on 1975-04-15 for underwater breathing apparatus.
This patent grant is currently assigned to Westinghouse Electric Corporation. Invention is credited to Wilbur J. O'Neill.
United States Patent |
3,877,425 |
O'Neill |
April 15, 1975 |
UNDERWATER BREATHING APPARATUS
Abstract
Breathing apparatus including first and second toroidal flexible
breathing bags, each positioned over a diver's shoulder and
extending down to the diver's waist area. The breathing bags are
interconnected and carbon dioxide absorbent means and gas admission
means are provided. First and second exhaust valves connected to
one of the breathing bags are positioned on opposite sides of the
diver and lie on a line passing through the vicinity of the
centroid of lung pressure.
Inventors: |
O'Neill; Wilbur J. (Severna
Park, MD) |
Assignee: |
Westinghouse Electric
Corporation (Pittsburgh, PA)
|
Family
ID: |
25262331 |
Appl.
No.: |
04/832,675 |
Filed: |
June 12, 1969 |
Current U.S.
Class: |
128/202.19;
128/205.17 |
Current CPC
Class: |
B63C
11/24 (20130101) |
Current International
Class: |
B63C
11/24 (20060101); B63C 11/02 (20060101); A62b
007/00 () |
Field of
Search: |
;128/142,202,142.2,142.3,142.4,142.5,147 ;9/32,342,341,340,337 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Dunne; G. F.
Attorney, Agent or Firm: Schron; D.
Claims
I claim as my invention:
1. Underwater breathing apparatus for a diver, comprising:
A. flexible breathing chamber means;
B. gas inlet means for supplying a breathable gas to said breathing
chamber means;
C. exhaust valve means connected to said flexible breathing chamber
means;
D. said flexible breathing chamber means being constructed and
arranged, and said exhaust valve means being operably positioned so
that there is always an inflated portion and a deflated portion of
said flexible breathing chamber means for every diver orientation
in the water; and
E. said inflated portion occupying approximately 40-60 percent of
the total available breathing chamber means volume.
2. Underwater breathing apparatus for a diver, comprising:
A. flexible breathing chamber means adapted to be worn by a
diver;
B. gas inlet means for supplying a breathable gas to said flexible
breathing means;
C. passageway means for communicating said flexible breathing
chamber means with said diver;
D. said flexible breathing chamber means having a front volumetric
portion and a back volumetric portion for said gas,
E. said front and back volumetric portions being communicative with
one another and being approximately equal and being approximately
equal above and below the diver's pressure centroid plane.
3. Apparatus according to claim 2 which includes;
A. first and second pressure exhaust valves located diametrically
opposed on said breathing chamber means whereby the pressure of
said breathing chamber will be equal to that of the diver's
internal pressure centroid.
4. Underwater breathing apparatus for a diver, comprising:
A. flexible breathing chamber means having first and second
interconnected sections;
B. each said section substantially in the form of a closed
loop;
C. gas inlet means for supplying a breathable gas to said flexible
breathing chamber means;
D. passageway means connected to said flexible breathing chamber
means for communication with said diver;
E. first and second exhaust valves connected to said flexible
breathing chamber means and positioned on a line adapted to pass
through the diver in the vicinity of the diver's pressure
centroid.
5. Apparatus according to claim 4 wherein:
A. each section of the flexible breathing chamber means is adapted
to be looped over a respective shoulder of the diver.
6. Apparatus according to claim 5 wherein:
A. each section of the flexible breathing chamber means is adapted
to extend down to approximately the diver's waist area.
7. Apparatus according to claim 4 wherein:
A. the first and second exhaust valves are connected to the same
section of the flexible breathing chamber means.
8. Apparatus according to claim 4 wherein:
A. each exhaust valve is settable to retain a certain pressure over
ambient; and
B. both exhaust valves are set to substantially the same
setting.
9. Apparatus according to claim 4 wherein:
A. each exhaust valve is settable to retain a certan pressure over
ambient; and
B. the first exhaust is adapted to be positioned on the front of
the diver,
C. the second valve is adapted to be positioned on the back of the
diver; and wherein
D. the first exhaust valve has a higher setting than the second
exhaust valve to eliminate exhaust bubbles in front of the diver's
face when in an upright orientation in the water.
10. Apparatus according to claim 4 wherein:
A. each exhaust valve is settable to retain a certain pressure over
ambient; and
B. the first exhaust valve is positioned in front of the diver;
C. the second valve is adapted to be positioned on back of the
diver; and
D. the first exhaust valve is at a position lower than the second
exhaust valve when the diver is in an upright orientation.
11. Underwater breathing apparatus for a diver, comprising:
A. a jacket for placement on said diver and having closure means on
the front side thereof;
B. a first flexible breathing bag connected to said jacket and
extending continuously in a closed loop around the front and back
of said jacket on one side of said closure means;
C. a second flexible breathing bag connected to said jacket and
extending continuously in a closed loop around the front and back
of said jacket on the other side of said closure means;
D means for interconnecting said first and second flexible
breathing bags;
E. means for admitting a breathable gas to at least one of said
flexible breathing bags; and
F. means connected to said flexible breathing bags for
communication with said diver.
12. Flexible breathing chamber means for an under water breathing
apparatus, comprising:
A. a first section of flexible material construction defining an
enclosed volume which extends around in a closed loop;
B. a second section of flexible material construction defining an
enclosed volume which extends around in a closed loop; and
C. means for interconnecting said first and second sections.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention:
Breathing apparatus utilizing flexible breathing bags.
2. Description of the Prior Art:
In the field of diving equipment there is a class of underwater
breathing apparatus which utilizes a flexible breathing chamber
into which a breathable gas is admitted. A carbon dioxide absorbent
is included in the breathing system and the diver inhales from and
exhales to the breathing chamber which is generally divided into an
inhalation and an exhalation section.
An exhaust valve is connected to the breathing chamber and will
open when the pressure within the breathing system exceeds a
predetermined value. This type of underwater breathing apparatus is
known to be quite diver position sensitive and causes large ranges
of undesirable inspiratory or expiratory effort. For underwater
work it is absolutely required to conserve as much as possible of
the diver's total expendable energy so that it may be fully applied
toward his specific task, or countering an emergency. The
increasing inspiratory or expiratory effort when the diver is in an
other than upright position causes unnecessary work for the diver
and tends to exhaust him earlier than would be the case with a
system requiring less breathing effort. In addition, large
inspiratory or expiratory pressures inhibit the proper cleansing of
carbon dioxide from his lungs.
It is therefore an object of the present invention to provide
underwater breathing apparatus having a flexible breathing chamber,
and which apparatus maintains the pressure of breathable gas in the
system within a range for diver comfort for any positional
orientation of the diver.
SUMMARY OF THE INVENTION
Briefly, underwater breathing apparatus is provided which includes
a flexible breathing chamber means having first and second
interconnected sections. When worn by a diver the flexible
breathing chamber means extends above and below the centroid of
lung pressure and in front of and in back of the diver. In the
preferred embodiment each of the first and second sections of the
breathing chamber means has an available gas volume substantially
defining a closed loop or toroid with a first section around the
other shoulder of the diver and the other section around the other
shoulder of the diver and extending to approximately the waist
area.
The first and second sections are interconnected via carbon dioxide
absorbent means and passageway means are provided for the diver to
be communicative with the breathing chamber means.
Valving means are provided and includes first and second exhaust
valves connected to the breathing chamber means and positioned on
opposite sides of the diver along a line which passes approximately
through the vicinity of the centroid of lung pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating a typical underwater
breathing apparatus utilizing breathing bags;
FIG. 2 is a view of a diver illustrating the centroid of lung
pressure and the plane passing through that centroid;
FIGS. 2A to 2D illustrate the centroid plane in relation to various
diver orientations;
FIGS. 3A through 3C illustrate breathing bag apparatus of the prior
art and various pressure considerations;
FIG. 4 illustrates a typical exhaust valve in sectional view;
FIGS. 5, 6, and 7 are curves illustrating breathing system pressure
relative to the pressure at the lung centroid for various diver
orientations and with the prior art apparatus as in FIG. 3A;
FIG. 8A is a three-quarter front view and FIG. 8B is a rear view of
a preferred embodiment of the present invention;
FIG. 9 is a schematic of the preferred embodiment;
FIGS. 10 and 10a illustrate the valving arrangement of the
preferred embodiment in relation to the centroid of lung
pressure;
FIGS. 11A through 11C illustrate breathing bag collapse with
respect to three diver orientations;
FIGS. 12 to 14 are similar to FIGS. 5 to 7 and show pressure
difference with the preferred embodiment;
FIG. 15 illustrates an alternative valving arrangement; and
FIGS. 16a and 16b illustrate a modified arrangement of breathing
bags.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, there is illustrated a typical prior art
underwater breathing apparatus commonly known as a semi-closed
system.
The apparatus includes a flexible breathing chamber means 10 having
first and second sections 10a and 10b. Section 10a is commonly
referred to as an inhalation bag and section 10b as an exhalation
bag.
Passageway means 12 including oral-nasal mask 16 connects the
inhalation bag 10a with the diver and connects the diver with the
exhalation bag 10b. The flexible breathing bags are also
interconnected through a carbon dioxide absorbent means 22.
A source of breathable gas 24 provides a breathable gas to the
breathing bags, by connection for example to exhalation bag 10b, by
means of an arrangement including a flow orifice 26 which governs
the flow rate of gas into the system, and a purge valve 27 for
quickly admitting large quantities of gas to the system when
activated by the diver.
Exhaust valve 30 is connected to breathing bag 10b and when the
pressure in the system, as evidenced by the pressure in exhalation
bag 10b, exceeds the ambient pressure at the valve 30 by a
predetermined amount, the valve 30 will open.
When breathing bags are incorporated into diving apparatus, the
hydrostatic pressure upon the bags is transmitted to the gas space
within the chest. Within the upper and lower limits of the external
hydrostatic pressure on the chest, there is an internal pressure,
conventionally referenced to an intermediate depth point in water,
which is the center of pressure, herein referred to as the centroid
of lung pressure. When the diver is provided with gas at this
pressure, there is no net chest volume change, because the lower
lobe compresssion and the upper lobe expansion of the lungs are
balanced. This centroid of lung pressure is illustrated in FIG. 2.
The centroid of lung pressure 34 is believed to be, for an average
man, located as illustrated in FIG. 2, at a point approximately 19
centimeters (cm) below, and 7 cm behind suprasternal notch 35 which
is the notch at the top of the sternum or breast bone. A horizontal
plane passing through the centroid of lung pressure 34 is
designated 36 and is herein referred to as the centroid plane.
Although the present invention will be described with respect to
this centroid of lung pressure there may, upon further study, or
with different diver communication means, be other points which
should be matched with respect to breathing system pressure.
Generically, the term "pressure centroid" will be utilized and will
mean a point, referenced to a diver, the hydrostatic pressure at
the depth of the point, being the most desirable breathing gas
system pressure to minimize the effort required by the diver to
breathe.
FIGS. 2A and 2D illustrate the constant horizontal orientation of
the centroid plane 36 with respect to various diver positions.
If a breathing bag apparatus would provide breathing gas to the
diver at a pressure approximating the pressure at the centroid 34,
the diver would not have to breathe under the excessive positive
and negative pressure conditions prevalent in most underwater
breathing apparatus incorporating breathing bags. Examples of
balanced, positive, and negative pressure breathing situations are
illustrated in FIGS. 3A to 3C.
FIGS. 3A is a side view of a diver wearing what is commonly termed
chest or front mounted breathing bags of which the right one, 10b,
is shown and having an exhaust valve 30 which is a spring loaded
valve with a knob or nut that can be turned to increase or decrease
the pressure in the breathing bag. A simplified sectional view of a
typical exhaust valve is illustrated in FIG. 4 to which reference
is now made.
The valve 30 includes a valve housing 37 and a flexible diaphragm
38 held in position by means of retaining nut 39. The flexible
diaphragm has a central aperture 40 and the diaphragm is forced
down onto valve seat 41 by means of spring 42, the construction
defining annular chamber 43.
The upper part of the spring 42 bears against spring retainer 50
through which passes rod 51 threadedly engaged with valve seat 41.
Adjusting nut 52 is provided in order to vary the spring
pressure.
The annular chamber 43 is connected to the breathing bag and the
pressure in it will be the same as the system pressure, herein
designated P.sub.S. If P.sub.V is the average ambient water
pressure acting on the flexible diaphragm to close the valve, then
P.sub.S = P.sub.V + S, where S is the equivalent pressure
contributed by the spring tending to close the valve. For any
P.sub.V, the greater the valve of S (that is, the greater the nut
41 is tightened down), the greater the pressure will be in the
breathing system.
When the pressure P.sub.S in the breathing system attains a value
just greater than P.sub.V + S, the flexible diaphragm 38 is forced
off of the valve seat 41 and breathing gas escapes to the
surrounding water medium through aperture 40. The escape of gas
will continue until the pressure within the breathing system
reduces to a value equal to the ambient pressure P.sub.V plus the
spring setting S. Referring once again to FIG. 3A, there is
additionally shown the centroid of lung pressure 34 and the
horizontal centroid plane 36 passing through it and through a lung
44 shown in outline.
In addition to the centroid plane 36, another plane must be
considered in the design of such breathing apparatus and that plane
is the collapse plane. The collapse plane as described herein is
the horizontal plane, the pressure at which equals the system
pressure. The collapse plane, which is always horizontal, may
separate the inflated and deflated portions of the breathing bag or
may be positioned below the breathing bag depending upon valve
setting. The collapse plane illustrated in the figures is pictured
at a point in the breathing cycle just at the end of expiration and
the beginning of inspiration when it is assumed that the exhaust
valve has just been opened and that the bag is at maximum inflation
as determined by the exhaust valve setting.
If, for the diver illustrated in FIG. 3A, the valve 30 is set at 24
cm, that is, the spring setting S is equivalent to a pressure equal
to 24 cm of water, then when the pressure within the breathing bag
10b reaches a value of the ambient water pressure on the valve plus
an additional 24 cm of water, the valve will open to maintain the
system pressure at P.sub.V + 24. For the diver's dimensions the
pressure thus established in the breathing system is equivalent to
a pressure at a point 24 cm deeper than the valve 30 and is
equivalent to the pressure at the centroid plane 36 acting on the
centroid of lung pressure 34. A collapase plane 46 is therefore
established and is coincident with the centroid plane 36. The
portion of the breathing bag 10b above the collapse plane 46 is
inflated and the portion below it is deflated.
Since the pressure within the breathing system is equal to the
pressure at the centroid plane 36, the diver will experience no
difficulty in breathing and the situation is referred to as balance
pressure breathing. Ambient water pressure is transmitted to the
lungs and since the pressure within the lungs is the same as the
breathing system pressure within the bag 10b, the portion of the
lungs 44 above the centroid plane 36 will have a pressure
differential thereacross directed outwardly and the pressure
differentail thereacross below the centroid plane 36 directed
inwardly, as depicted by the arrows.
FIG. 3B illustrates an example of negative pressure breathing. The
setting of valve 30 is equivalent to 12 cm of water to thereby
establish the system pressure P.sub.S within the bag 10b at a value
equal to the pressure 12 cm below the valve 30. The collapse plane
46 is thus established at this point and it is seen that the
pressure within the system as determined by the collapse plane is
less than the pressure acting on the centroid 34 by an amount
equivalent to 12 cm of water. In the vicinity of the diver's lungs,
the hydrostatic pressure outside and below the collapse plane 46 is
greater than the pressure within the lungs, the lungs being at a
pressure equal to the pressure at the collapse plane 46. The diver
therefore must provide extra muscular energy to pull the breathing
gas in; the pressure difference is acting inwardly over a major
portion of the lungs, as depicted by the arrows.
FIG. 3C illustrates an example of positive pressure breathing. The
exhaust valve 30 is set to 34 cm thereby establishing a system
pressure P.sub.S equal to the ambient pressure at the valve P.sub.V
plus an additional 34 cm of water thereby defining the collapse
plane 46 at a position 10 cm below the centroid plane 36. Since the
pressure P.sub.S within the breathing bag 10b is greater than the
ambient water pressure acting on the lungs, the diver will
experience no difficulty in inhaling, however extra energy is
required to exhale against the increased positive pressure
encountered during the latter part of exhalation. As depicted by
the arrows in lung 44 the pressure difference acts in an outward
direction.
Since the system pressure is determined by the ambient pressure at
the valve plus a spring pressure, the exhaust valve under water
will always establish a collapse plane hydrostatically deeper than
itself by a constant amount S.
Considering a piece of apparatus as in FIGS. 3A, 3B or 3C, a
typical valve setting may be in the order of 20 cm. That is, the
exhaust valve 30 is set to retain a pressure of 20 cm of water over
ambient, which setting is approximately equivalent to a pressure of
one-third pounds per square inch. This setting produces a collapse
plane 20 cm below the valve location and 4 cm above the centroid
plane. The pressure in the breathing system therefore is 4 cm less
than the pressure exerted on the centroid of lung pressure,
however, the 4 cm difference is well within a tolerable range for
diver breathing comfort. This 4 cm difference will exist as long as
the diver remains in a vertical position. As the diver assumes
different positions the difference between the system pressure and
the pressure at the centroid plane varies. This situation is
graphically illustrated, to an approximation, in FIGS. 5, 6, and 7
wherein the vertical scale represents the difference between the
collapse plane pressure (which is the pressure in the breathing
system) and the centroid plane pressure (which is the desired
pressure from a physiological stand point), the vertical scale
being a pressure difference .DELTA. P in centimeters of water. The
horizontal scale represents diver rotation in degrees.
In FIG. 5 the diver is rotated forwardly about an axis passing
through the centroid of lung pressure. In all diver positions the
system pressure P.sub.S is always S units of pressure greater than
the pressure P.sub.V at the valve and the collapse plane 46 is
always at a deeper position than the valve.
When the diver is in vertical position A (0.degree. of rotation)
the pressure P.sub.S within the system will be 4 cm less than the
pressure at the centroid plane 36, recalling that the valve setting
S is 20 cm and the distance from the valve to the centroid plane is
24 cm. At position A therefore there exists a condition of negative
pressure breathing, as in FIG. 3B but within approximate tolerable
limits as indicated by the shaded area between .+-. 6 cm. Further
rotation to position B, the 45.degree. position, will lower the
collapse plane 46 to a point approximately 3 cm below the centroid
plane thereby increasing the system pressure to a value 3 cm
greater than the pressure at the centroid plane, a condition of
positive pressure breathing as in FIG. 3C but still within
tolerable limits. In the 90.degree. position C the valve lies in
the centroid plane so that the system pressure is exactly 20 cm
greater than the pressure at the centroid plane. Further rotation
to position D at 135.degree., increases the degree of positive
pressure breathing with the pressure difference .DELTA. P
increasing to a maximum when the valve is directly below the
centroid of lung pressure as illustrated in the 180.degree.
position E. Since the valve is 24 cm deeper than the centroid of
lung pressure and the valve setting is 20 cm then the difference
between the system pressure and optimum pressure at the centroid
plane is 24 + 20 or 44. This curve is symmetrical about the
180.degree. position and further diver rotation is illustrated at
positions F, G and H representing respectively rotations of
225.degree., 270.degree. and 315.degree.. At 360.degree. the diver
is in the same orientation as position A.
It is seen from FIG. 5 therefore that with an initial setting for
comfortable breathing in an upright position, the diver would be
extremely limited in the degree of forward rotation since for
rotation from about 54.degree. to about 306.degree. he would be
experiencing positive pressure breathing outside of the tolerable
range.
FIG. 6 is similar to FIG. 5 except that the diver rotation is
laterally about an axis passing through the centroid of lung
pressure. With a valve setting of 20 cm the diver experiences a
pressure difference between the system pressure and pressure at the
lung centroid ranging from approximately -10 cm to +48 cm. Diver
positions A to H correspond to 45.degree. increments as in FIG. 5.
It is seen from FIG. 6 that for most positions of rotation an
undesirable situation is presented.
If the diver in position C of FIG. 5 is rotated about a horizontal
axis drawn longitudinally down his body through the centroid of
lung pressure, then the curve of FIG. 7 results. 45.degree.
increments of rotation are illustrated in respective positions A to
H and with a valve setting of 20 cm the diver is always outside of
the tolerable range and is constantly overpressured.
The breathing apparatus of the present invention maintains system
pressure very close to the pressure at the centroid plane, for any
conceivable positional orientation of the diver in the water. A
preferred embodiment of the apparatus is illustrated in FIGS. 8A
and 8B.
The apparatus includes a flexible breathing chamber means 60 having
a first section 60a and a second section 60b, each section having
an available gas volume defining a closed loop and being somewhat
toroidal in shape. The sections are worn around respective
shoulders of the diver and extend to the vicinity of the hip area.
The first section 60a may constitute an inhalation breathing bag
and the second section 60b may constitute an exhalation breathing
bag. The breathing bags, which may be fabricated from flexible
breathing bag materials known to those skilled in the art, are
fastened to a diving vest or jacket 62 having closure means 63
extending down the front thereof. Conventional weighting means 66
may be worn around the diver's waist and an easily accessible purge
valve 69 is also included. Weighting means such as described and
claimed in copending application Ser. No. 832,670, filed June 12,
1969, now U.S. Pat. No. 3,656,196, and assigned to the same
assignee as the present invention, may also, and preferably, be
used.
The breathing bags 60a and 60b are interconnected via a carbon
dioxide absorbent canister 72 positioned on the back of the diver.
Passageway means 75 including an oral-nasal breathing mask 78, for
example, communicates the diver with the breathing bags.
A breathable gas is provided to the breathing system by means of
gas supply 80 or by means of a remote supply and umbilical, in
which case the gas supply 80 would be for emergency purposes.
The breathing system includes exhaust valve means in the form of
first exhaust valve 83 and second exhaust valve 84 with the valves
83 and 84 being positioned on opposite sides of the diver and being
connected into the breathing system, the connection being by way of
example to exhalation breathing bag 60b.
FIG. 9 is a schematic diagram of the apparatus of FIGS. 8A and 8B
and additionally shows gas inlet means 87 for supplying a
breathable gas through flow orifice 88 to the breathing bags. The
remaining components have been given the identical reference
numerals as their counterparts in FIGS. 8A and 8B. A breathable gas
such as from the supply 80 is continually provided to the
inhalation breathing bag 60a through the gas inlet means 87 and at
a rate determined by the flow orifice 88. When the diver inhales,
the gas from the inhalation breathing bag 60a is supplied to the
diver via passageway means 75 and the oral-nasal mask 78. Upon
exhalation, the exhaled gas passes into exhalation breathing bag
60b via the passageway means 75. The breathing bags 60a and 60b are
interconnected through the carbon dioxide absorbent canister 72 and
the pressure in both breathing bags is the same. Each time a diver
inhales he is supplied with gas that has been treated to remove the
carbon dioxide and upon exhalation when the pressure within the
system exceeds a predetermined value relative to the ambient water
pressure, one or both of the valves will open.
It has been stated that the valves 83 and 84 are on opposite sides
of the diver. In addition, and as illustrated in FIG. 10, the
valves 83 and 84 (in particular the center of aperture 40 in FIG.
4) lie on a line 90 which passes through the centroid of lung
pressure 34. As a practical matter, due to equipment variation,
diver size variation, and allowable tolerances, the line 90 passes
through the vicinity of the centroid of lung pressure 34, for
example within several centimeters of it.
Relative to the generic concept of pressure centroid, the valves
would be located on either side of the diver on a line passing in
the vicinity of the pressure centroid. For example if the pressure
centroid has been determined to be at point 34' then the exhaust
valves designated 83' and 84' lie on the line 90' passing through
34'.
FIG. 10A shows a top view of the diver and the valves 83 and 84
positioned as shown in FIGS. 8A and 8B. It is not necessary that
the line 90 have the orientation as shown. For example and with
reference to the valves 83' and 84' the line 90' may pass through
the centroid 34' in a diagonal manner as illustrated.
The toroidal breathing bags 60a and 60b are constructed and
arranged so that approximately half the internal volume or capacity
of the flexible breathing chamber means 60 is above, and the
remainder below the centroid plane 36. With the individual
breathing bags 60a and 60b being of equal capacity, the aforestated
relationship of volume distribution around the centroid plane will
be true for any diver orientation. When inflated, the breathing
chamber means may typically contain 8 liters of breathing gas
distributed, as governed by diver orientation, between the toroidal
bags 60a and 60b.
Examining for a moment just the interconnected breathing bags by
themselves, if a quantity of gas is placed into the breathing
system such that the collapse plane 46 is coincident with the
centroid plane 36, then for any conceivable orientation of the
breathing bags in the water, that same quantity of gas is afforded
a potential volume and the collapse plane remains coincident with
the centroid plane. There are other factors howevr to be
considered; gas is being supplied and used by the diver, and valves
83 and 84 are relieving the pressure within the system. The
apparatus does however maintain the collapse plane 46 very close to
the centroid plane 36 for all diver orientations.
If, in FIG. 10, the distance between valves 83 and 84 is D and the
lung centroid 34 is approximately positioned at D/2, then the
valves 83 and 84 should be set to a value of D/4 for maximum diver
comfort. If the valves are otherwise positioned an appropriate
setting is chosen. By way of examle if the diver's dimension from
his chest to his back along line 90 is 22 cm and valves 83 and 84
are each 1 cm away from the diver than the distance D would be 24
cm and each of the valves 83 and 84 may be set to a value of 6 cm.
That is, with the valves 83 and 84 having a construction and
operation as previously described, the spring setting S would be 6
cm and the valve would open when the system pressure reached a
pressure of 6 cm of water greater than the ambient pressure at the
valve.
FIG. 11A illustrates the relationship of the collapse plane 46 to
the centroid plane 36 with the diver in an upright position and
with a valve setting of 6 cm. The vertical distance between the two
planes is 6 cm and the system pressure is determined by the
location of the collapse plane. FIG. 11A and subsequent FIGS. 11B
and 11C portray the collapse plane just at the end of exhalation
and at the beginning of inhalation.
If the diver in FIG. 11A rotates 180.degree. he will be in an
orientation illustrated in FIG. 11B. The two valves 83 and 84 with
their respective 6 cm setting define the collapse plane 46, 6 cm
below the centroid plane 36. Since the valves 83 and 84 are in the
same horizontal plane in both FIGS. 11A and 11B, one or both of
these valves will be operable to exhaust gas if the system pressure
tries to exceed the pressure at the collapse plane. For all other
diver orientations, the valve closest to the surface of the water
will always be the controllling valve. By way of example, in FIG.
11C the diver is in a prone position with valve 84 directly above
the centroid 34 and valve 83 directly below it. Let it be assumed
that the ambient pressure at the upper valve is P.sub.1 and the
ambient pressure at the lower valve is P.sub.2. Since the lower
valve is at a greater depth, P.sub.2 is always greater than
P.sub.1. The upper valve will open when the pressure within the
system reaches P.sub.1 + S and the lower valve will open if the
system pressure reaches P.sub.2 + S. However P.sub.1 is less than
P.sub.2 and system pressure never reaches P.sub.2 + S since the
upper valve opens when the system pressure reaches the lesser
pressure P.sub.1 + S to thereby maintain a system pressure of
P.sub.1 + S. With a valve setting of 6 cm, in FIG. 11C the collapse
plane 46 is 6 cm below valve 84 and is situated above the centroid
plane 36.
In FIGS. 12, 13 and 14 there is plotted, for the preferred
embodiment of the present invention, the difference between
collapse plane pressure and centroid plane pressure as a function
of diver rotation. The vertical and horizontal scales are the same
for all three curves and are identical to those illustrated in
FIGS. 5, 6 and 7.
In position a of FIG. 12, the diver is in an upright orientation
and with both valves 83 and 84 set to 6 cm the collapse plane 46 is
established 6 cm below the centroid plane 36. As the diver rotates
forwardly about the centroid 34, valve 84 is brought to a position
closer to the surface than valve 83 bringing the collapse plane 46
to a position a few centimeters above the centroid plane 36 at a
diver position B. At position C the diver experiences maximum
negative pressure breathing, however only to the extent of 6 cm,
within the tolerable range. Continued diver rotation brings the
curve back down to a positive pressure breathing situation in
position E whereupon the curve is repeated for the diver rotating
from the up-side-down positionn E to the vertical position which
occurs at 360.degree.. Whereas in the prior art apparatus a maximum
pressure difference of 44 cm was encountered, for the same
rotation, the apparatus of the present invention allows a maximum
excursion of only 6 cm.
In FIG. 13 illustrating diver rotation as described in FIG. 6, both
the front and rear mounted valves remain in the same horizontal
centroid plane and since the valves are set at 6 cm, the collapse
plane is established 6 cm below the centroid plane for all
360.degree. of diver rotation. For the prior art apparatus
illustrated in FIG. 6, there was experienced a maximum positive
pressure breathing situation to the extent of 47 or 48 cm. FIG. 13
shows the substantial improvement obtained with the present
invention.
Diver rotation in FIG. 7 produced, with prior art apparatus, a
maximum pressure difference of approximately 34 cm at the
90.degree. position. FIG. 14 illustrating the same rotation with
the apparatus of the present invention results in a curve with a
maximum excursion of 6 cm.
The flexible breathing chamber means of the present invention
extends above and below the centroid plane so that the available
volume above the centroid plane is approximately equal to the
available volume below it. When breathable gas is admitted to the
system, there is always an inflated portion of the breathing
chamber means above the centroid plane and a deflated portion below
it. The junction between the inflated and deflated portions, as
defined by the collapse plane, may vary from 6 cm below the
centroid plane to 6 cm above it, representing approximately a range
of 60 to 40 percent inflation respectively. By incorporating one or
more valve means which varies its setting in accordance with
positional orientation, the collapse plane may be substantially
coincident with the centroid plane for all diver orientations. One
such type of valving means is described and claimed in copending
application Ser. No. 832,671 filed June 12, 1969, now U.S. Pat. No.
3,841,348, and assigned to the same assignee as the present
invention.
The deflated portion of the breathing chamber means for one
orientation may be the inflated portion for another orientation. In
other words for varying diver positions there is always a place for
the gas to go, other than out the exhaust valve or valves. This
arrangement minimizes buoyancy changes for various changes in diver
orientation. By way of example, and with reference to FIG. 7, in
the 90.degree. diver position C both bags are fully inflated.
Rotation of the diver to the 270.degree. position G would
substantially deflate the lowermost breathing bag and contribute to
an undesirable net buoyancy change. With the present apparatus and
with reference to FIG. 14, in the 90.degree. diver position C
substantially only the uppermost breathing bag is inflated, this
situation remaining unchanged in the 270.degree. position G.
By way of further example and with reference to FIG. 6, in diver
position A the breathing bags are almost entirely inflated and
rotation to the 270.degree. position G would substantially deflate
the lower breathing bag. By comparison, in FIG. 13, the same amount
of gas is present in the breathing chamber means in diver position
A as in diver position G.
With the diver in an upright orientation the two valves 83 and 84
of FIG. 10 are on the same horizontal plane, and with equal valve
settings, either one or both of the valves will exhaust. To
eliminate bubbles in front of the diver's face, the valve 84 on the
diver's back may be set to a slightly lower setting than valve 83
to insure that it will open before valve 83. For equal valve
settings valve 84 on the back of the diver may be made to exhaust
first when the diver is in an upright orientation by means of the
arrangment illustrated in FIG. 15. With equal valve settings, valve
84 is placed at a position in the water closer to the surface and
therefore at a lesser ambient pressure than valve 83. The valves
however still remain on line 90 which passes through the centroid
34.
The breathing bags 60a and 60b have been shown by way of example to
be interconnected but independent. FIGS. 16A and 16B show a
variation wherein the flexible breathing chamber means 98 includes
interconnected first and second sections 98a and 98b, however they
are joined as a single entity.
There has been provided therefore an underwater breathing apparatus
which minimizes the difference between desired pressure and actual
pressure of the breathing gas supplied, for all conceivable diver
orientations in the water. In addition, the arrangement insures
that the flexible breathing chamber means remains inflated to
within a certain range, thus minimizing buoyancy variations and
reducing diver moment problems.
Although the present invention has been described with a certain
degree of particularly, it should be understood that the present
disclosure has been made by way of example and that modifications
and variations of the present invention are made possible in the
light of the above teachings.
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