[0001] This invention relates to self-contained portable breathing apparatus for self rescue
use in emergency situations and for periodic use by a patient with respiratory illnesses.
[0002] Portable breathing units which provide a user with a short term supply of breathable
gas without relying on the potentially contaminated or rarified available atmosphere
are becoming standard safety equipment for miners. Portable air supplies have application
in other industries where high levels of air contamination may be present, in fire
fighting, at high altitudes, or for patients who may periodically experience breathing
difficulties such as those with asthma or emphysema.
[0003] Portable breathing units are generally designed to provide the user with a constant
short term supply of oxygen while permitting the user free use of his hands, a feature
essential, for example, in a mine escape unit where the user may need to climb or
dig his way to freedom. Such a portable breathing unit is contained in a case which
is portable and which may be strapped to the user at the time of use. The apparatus
within the case includes an inhalation device, e.g., a mouthpiece, a bladder reservoir
of breathable air, a supply of oxygen, either in pressurized or chemical form, to
replenish the oxygen which is used, and a scrubber to remove waste products of respiration
from exhaled gas.
[0004] The scrubber generally contains a bed of chemicals reactive with carbon dioxide,
the primary by-product of animal respiration. An efficient and commonly used chemical
for removing carbon dioxide from the air is lithium hydroxide which is lightweight
and reacts readily with carbon dioxide. In addition, other material such as molecular
sieves may be used in conjunction with the carbon dioxide reactive material for-removing
excess water and hydrocarbons. An example of an air purification unit which utilizes
lithium hydroxide in conjunction with a molecular sieve, i.e., zeolite material, is
described in U.S. Patent No. 4,005,708.
[0005] Emergency portable breathing apparatus are commonly sealed in a container or case
preventing atmosphere entering the breathing apparatus from depleting the scrubbing
material. Sealed cases further avoid exposure of the apparatus to air-carried particles
and corrosive chemicals which could lead to malfunction of the apparatus. The maintenence
of the hermetic seal is relied upon by high risk workers such as miners to assure
the integrity of their emergency equipment.
[0006] As a means of determining whether the hermetic seal has been broken, windows, such
as are described in U.S. Patent No. 4,019,509, provide a view of hygroscopic material,
within the case, that changes color as it collects moisture. A color change, of course,
indicates the introduction of moisture and the breaking of the hermetic seal. Another
commonly used examination procedure is to submerge the case in water whereby a broken
seal may be detected by the presence of air bubbles. Neither of these tests, of course,
provides for examination of the equipment within the case. It is desirable to have
breathing apparatus and cases therefore which permit the immediate inspection, not
only of the hermetic seal, but of the apparatus within the case.
[0007] It is desirable that portable breathing equipment be as lightweight as possible.
Each pound which can be removed from a miner's heavy load makes his work that much
easier. Weight becomes an especially critical factor in emergency situations where
a miner has to climb or otherwise maneuver to safety under adverse circumstances.
Also, elderly persons or persons weak from emphysema do not want to be burdened with
heavy units.
[0008] Among the discomforts of breathing through portable breathing apparatus of the above-described
kind is the elevated temperature of the breathable air which generally results from
the scrubbing of the carbon dioxide. Two reactions occur when carbon dioxide passes
through a lithium bed:
[0009] Reaction (1) is endothermic and removes a mole of carbon dioxide for each mole of
lithium hydroxide. Reaction (2) is exothermic and only removes one half mole of carbon
dioxide for each mole of lithium hydroxide. Unfortunately, the reaction produces heat,
and hence, the scrubbing of carbon dioxide produces considerable amounts of heat.
The temperature in a typical lithium hydroxide scrubber may reach 275°F whereas it
is uncomfortable to inhale air above 115°F.
[0010] Accordingly, it is desirable to minimize the heating effects of the scrubber as much
as possible and to provide breathable gas to the user at close to ambient temperatures.
This is accomplished in the breathing loop in the breathing bag.
[0011] In order to be used in mine applications, the portable emergency breathing apparatus
must meet various standards. To meet one of these standards, the apparatus is operated
as though a man were using it while doing heavy work for about one and a half hours.
In such a test, it has been found that carbon dioxide level may reach the level of
1-1/2 percent by volume of the air being inhaled and this level is too high. Although
the scrubber has enough lithium hydroxide to last one and a half hours, the scrubber
wasn't performing adequately until means were provided to increase the transit time
of the air through the scrubber so that the carbon dioxide level could be maintained
below 1.5 percent.
[0012] In emergency escape equipment, which will hopefully never be used and used on rare
occasions if at all, reusability of the equipment and oxygen cannister is desirable
but of secondary concern. While portable breathing apparatus is intended to provide
a continuous short term supply of breathable air, there are applications, both in
emergency situations and in medical applications, where it is desirable that the breathing
apparatus be used intermittently to supplement the user's available air supply over
an extended period of time. It may, for example, be sufficient for a patient who experiences
chronic breathing difficulties, to rejuvinate himself with an occasional breath of
oxygen-enriched air from a portable unit. If, as is generally true in the case of
units from which oxygen is produced by a chemical reaction, the oxygen supply cannot
be turned off once activated, the oxygen supply is quickly depleted irrespective of
the patient's needs. Thus, it is desirable that the apparatus may be shut off and
turned on at will.
[0013] In addition to removing carbon dioxide from the exhaled air, scrubbers commonly include
material, e.g. molecular sieve material, which removes water vapor and other impurities
from the exhaled air for recycling. Users of emergency portable air supplies are encouraged
to hold their breath or breathe as little as possible prior to donning the emergency
equipment, a measure intended to protect the person from inhaling poisonous gasses.
Unfortunately, in an emergency situation, this advice may go unheeded as a result
of user uncertainty or as a result of unavoidable time delay in donning the apparatus,
and, consequently, the first breath, which the user exhales, may contain significant
amounts of impurities. Desirably, portable oxygen equipment anticipates the immediate
exhalation of foul air into the mouthpiece.
[0014] Accordingly, a general object of the invention is to provide a new and improved portable
breathing apparatus.
[0015] Another object of the invention is to minimize the effects to the user of the exothermic
carbon dioxide removing reactions in the scrubber.
[0016] A still further object of the invention is to provide a breathing appratus which
is reusable and inexpensively refurbished after use.
[0017] Another object of the invention is to provide lighter weight emergency breathing
apparatus.
[0018] These and other objects and advantages of the invention will become more apparent
from the following detailed description of the apparatus in reference to the accompanying
drawings in which:
FIGURE 1 is a perspective view of a portable breathing unit embodying various features
of the present invention;
FIGURE 2 is a front elevation view of the unit shown in FIGURE 1;
FIGURE 3 is a side elevation view of the unit with the case cut away;
FIGURE 4 is a side elevation view of the closed case;
FIGURE 5 is a diagrammatic view of the valve system used in the breathing unit to
regulate the flow of fresh oxygen;
FIGURE 6 is a rear elevation view of the air bag utilized in the unit;
FIGURE 7 is a plan view of the collapsed air bag illustrating how it is folded for
storage within the case;
FIGURE 8 is an elevation view of an air scrubber partially in cross section utilized
in the apparatus;
FIGURE 9 is an elevation view, partially cut away, of the user mouthpiece and exhalation
and inhalation tubes.
FIGURES 10 and 11 are views similar to FIGS. 1 and 2, respectively, illustrating another
embodiment of the invention.
FIGURE 12 is a diagrammatic illustration of air flow through the apparatus.
FIGURE 13 is a diagrammatic illustration of carbon dioxide levels in the air flow.
[0019] Illustrated in Figure 1 is an emergency breathing apparatus 10 which, in times of
emergencies or breathing difficulties, may be used to provide air to the user. For
example, the apparatus 10 may provide a full hour of air for the user in heavy exertion
and heavy breathing situations. Breathable air is contained in a flexible bladder
12 or air bag which expands and contracts as the user inhales air therefrom and exhales
thereinto. Oxygen is supplied from a container 14 through appropriate valves and regulators
to the air bag 12 through a conduit 16 for continuously replenishing oxygen used in
respiration. The user inhales air through an inhalation conduit 18 connected directly
to the air bag 12 and to an inhalation port 20 of a user mouthpiece 22 and exhales
through an exhalation port 24 of the mouthpiece. The exhaled gasses flow through an
exhalation conduit 26 to an inlet port 28 of a scrubber 30 (Fig. 3). After being cleaned
of respiration by-products, primarily carbon dioxide, in the scrubber 30, the air
exits through an outlet port 32 (Fig. 3) of the scrubber and flows through a return
conduit 33 to the air bag 12 where it is replenished with oxygen.
[0020] The breathing apparatus 10 is contained in a case 34 (Fig. 4) which includes a shell
36 having a rear surface 38 adapted for lying against the user's body, e.g. his chest,
and a cover 40 therefor. The shell 36 is attached to an appropriate harness 42 which,
when worn by the user, allows him to wear the apparatus 10 with his arms free. The
front cover 40 is sealed to the shell 36 with means such as a gasket 114 (Fig. 4)
or the like providing a sealed region 44 around the apparatus. Maintenence of the
hermetic seal provides a strong indicia that the apparatus has not been tampered with
and is in good working order.
[0021] In accordance with the present invention, the self contained breathing apparatus
10 is lightweight and relatively inexpensive in operation and is constructed to allow
the user to control his demands for oxygen and the usage thereof in order to conserve
the oxygen over a prolonged period of time and usage. In this connection, the oxygen
bottle 14 is provided with an "on-off" valve 46 (Fig. 5) which can be manually operated
by a user-actuated knob 47 (Fig. 1) between an open position to allow oxygen flow
from the bottle and a closed position at which the flow is stopped. This is in contrast
to some prior art systems in which the oxygen continues to flow to empty the bottle
once the valve was open, thereby severely limiting the time usage and the availability
of oxygen to a one time usage situation. Further, the conservation of oxygen is improved
by the use of a demand regulator means 48 (Fig. 5) and the air bag 12 and scrubber
30 which allows reuse of the air exhaled by the user after it has been scrubbed of
carbon dioxide by the scrubber. The demand regulator 48 allows oxygen to flow to the
air bag 12 in accordance with the usage needs of the user. Thus, the apparatus 10
is capable of providing low constant flow and a very high demand oxygen flow, such
as to miners who are doing heavy labor in an emergency situation, or of providing
very low oxygen demand flow as where an emphysema patient needs only a few breaths
of oxygen enriched air on a short term and infrequent basis. The preferred oxygen
bottle 14 is provided with means such as a fitting 50 to facilitate its being refilled.
The ability to refill is important to allow the apparatus to be used repeatedly.
[0022] Preferably, the weight of the apparatus 10 is reduced by using an oxygen bottle 14
formed of a metalic lining and a non-metallic synthetic material such as wound fiber
glass forming a composite structure and by using a plastic material to form the carrying
case 34 for the apparatus rather than heavier all metal bottles and metal carrying
cases. Preferably, the carrying case 34 is formed of transparent plastic which allows
visual examination of the internal contents of the case to reveal any damage to the
apparatus which might occur as a result in banging the case while being transported.
The preferred case 34 is also sealed. The transparent case allows visual inspection
of the seal and moisture indicating particles or material 115 are not neccessary but
may be used. This material changes color when exposed to moisture, thereby visually
warning the user that the hermetic seal for the case has been breached.
[0023] In accordance with a further aspect of the invention, air from the scrubber 30 flows
to the air bag 12 for mixing with incoming oxygen and is allowed to cool before being
returned through the inhalation conduit 18 which bypasses the scrubber 30 returning
scrubbed air to the mouthpiece 22 so that the scrubbed air is not reheated when returning
to the user's mouthpiece. The preferred chemical bed removes carbon dioxide from the
exhaled air primarily in an exothermic reaction which increases substantially the
temperature of the exhaled air which should, for the comfort of the user, be reduced
in temperature before entering the mouth of the user. The perferred scrubber 30 includes
an exterior housing or metal cannister 52 with heat radiating means 54.
[0024] Heretofore, scrubbers were not constructed with the view that the miner or other
user may already have a breathful of hydrocarbons when he first puts on the mouthpiece,
and the user was cautioned against exhaling large amounts of hydrocarbons into the
scrubbing means. In the scrubber 30 of this invention; however, a molecular sieve
material 56 (Fig. 8) is placed before a carbon dioxide reactive material 94 to remove
hydrocarbons. Preferably a second molecular sieve material 60 is placed after the
reactive material 58 to likewise clean the air before it is being discharged into
the breathing bag 12. The molecular sieve also absorbs water keeping the filter dry
and breathing resistance low.
[0025] The air bag 12, which is designed to hold about 5 liters S.T.P. of readily available
air, is formed of material that flexes easily to minimize breathing resistance and
to be folded into a compact configuration when not in use. The air bag 12 as best
seen in Figure 1, is tubular in shape having a front panel 62 and a back panel 64
sealed together, e.g., with heat seals,. and a pair of side panels 66. When the cover
40 of the case 34 is removed from the shell 36, the air bag 12 extends generally horizontally
beyond the sides of the shell. Prior to use, the air bag 12 is folded in three, as
best seen in Figure 7, with both ends folded against the middle. As soon as air or
oxygen enters the bag 12, the bag unfolds and expands to its inflated configuration
(Fig. 1). The bag 12 has an inlet port 67 through which oxygen demand regulator enters,
an outlet port 68 connected to the inhalation conduit 18 and a return port 70 connected
to the return conduit 33. The air bag 12 also has a relief valve means 72 to relieve
excess pressure assuring low breathing resistance.
[0026] Heretofore, metal containers were used to contain high pressure oxygen or chemicals
which react to produce oxygen, and the apparatus 10 of the present invention reduces
weight through use of a composite cylinder 14. Preferably the cylinder 14 is formed
of a wound fiberglass member with an aluminum thin wall inner lining. Such cylinders
14 are capable of holding oxygen at upwards of 3000 psi, and a cylinder which carries
a one hour supply of oxygen, i.e. 157 liters S.T.P., may weigh less than 2 pounds.
Furthermore, such cylinders 14 may be used over and over again, and the inlet fitting
50 allows the oxygen cylinder to be recharged after use.
[0027] The conduit 16 from the oxygen demand regulator to the air bag 12 has appropriate
gauges and regulators for controlling the flow of oxygen to the air bag thereby prolonging
the supply of available oxygen. A cylinder pressure gauge 74 in the valve 46 measures
the cylinder pressure at all times for ascertaining the pressure and providing an
accurate indicion of the remaining oxygen within the cylinder 14. When the apparatus
10 is used, the on-off valve 46 is opened by the knob 47 to inflate the air bag 12
with substantially pure oxygen and provide immediate relief for an oxygen-low user.
The on-off valve 46 further provides for intermittent use of the apparatus 10, a feature
particularly advantageous in prolonging usefulness of the apparatus in situations
where the user may rely partially on the ambient atmosphere or may be at rest in a
hazardous environment. Such a feature is unavailable in chemically generated oxygen
supplies which, once activated, continue to produce oxygen until exhaustion of one
of the reactants. A valve unit 76 (Fig. 5) includes a reducing regulator 78 which
reduces the pressure to a level which can be utilized by the demand regulator. From
the pressure reducing regulator 78, the air flows in one of two branches (Fig. 5),
through either a constant flow valve 80 or the demand regulator 48. The constant flow
valve 80 provides about 1.5 - 1.8 liters S.T.P. of oxygen per minute to the bag 12,
i.e., enough to sustain a moderately active man. The demand regulator 48 is also responsive
to the downstream pressure in the air bag 12 replenishing the extra oxygen used up
by an active man.
[0028] The mouthpiece 22 (Fig. 9) includes a flange 82 formed of flexible material insertable
into a user's mouth and shaped to fit against the inner surface of the user's lips.
For gripping by the user's teeth, a pair of bits 84 are provided on and extend from
the flange 82 on either side of a breathing opening 83, and the user grips the bits
84 with his teeth. The inhalation port 20, to one side of the mouthpiece, carries
a valve seat 85 to support a one-way inhalation valve 86 (Fig. 9) which moves to a
closed position to close the passageway through the inhalation port 20 when the user
exhales and places a positive pressure thereon and moves to an open position to open
the passageway when the user inhales and produces a negative pressure thereon. The
exhalation port 24 on the other side of the mouthpiece 22 carries a one-way exhalation
valve 87 mounted to the same valve seat 85 which operates in the reverse, moving to
open the passageway through the port when the user exhales a positive pressure thereon
and close the passageway when the user inhales and places a negative pressure thereon.
Thus a one way flow of air is established through the apparatus 10, the user always
drawing fresh air directly from the air bag 12 as he inhales and exhausting used air
through the scrubber 30 when he exhales.
[0029] Location of the inhalation valve 86 and exhalation valve 87 at the mouthpiece 22
rather than at a remote location, as is the case in some breathing units, reduces
dead space, i.e., the space between the lungs and the mouth and including the region
of the breathing apparatus up to the valves as an extension of the mouth. Reduction
in dead space achieves a corresponding reduction in oxygen usage.
[0030] The inhalation valve 86 and exhalation valve 87 are preferably adapted to equalize
breathing loop resistance to inhalation and exhalation. In the closed loop, the inhalation
conduit 18 is connected directly to the breathing bag which in turn is supplied by
the oxygen bottle 14 while the exhalation conduit 26 is connected to the flow resistant
scrubber 30. Thus, the resistance is higher on the exhalation side. To equalize resistance
for more natural breathing, the inhalation valve 86 is designed with greater breathing
resistance than the exhalation valve 87.
[0031] The unitary valve seat 85 in the mouthpiece 82 has an inhalation opening 121 encircled
by an annular flange 122 on the side of the valve seat 85 facing the user and exhalation
opening 123 encircled by an annular flange 124 facing away from the user. Each of
the openings 121, 123 is disposed eccentrically relative to the corresponding flange
122, 124, and the valves 86, 87 are held to the valve seat 85 at their centers and
are centered relative to the valve flanges to establish peripheral contact therewith
to close off flow through the openings.
[0032] As a preferred means to equalize the pressure, the inhalation valve is an umbrella
valve 86 and the exhalation valve is a disc valve 87. The inhalation or umbrella valve
136 is a unitary piece of flexible material, e.g, silicone rubber, having a stem 125
which extends through an aperture 126 in the valve seat 125 relative to the flange
and a flap 127 which seats along the annular flange 122. The stem 125 includes a cylindrical
center segment 128 matched in diameter and length to the aperture 126, a conical upstream
segment 129 having a maximum diameter greater than the opening and a cylindrical downstream
segment 130 greater in diameter than the opening. When the conical upstream segment
129 is pulled through the aperture 126, the stem achieves an interference fit with
the valve seat flange 122 sealing the aperture and securely holding the valve 87 along
the valve seat 85. The flap 127 includes a circular region 131 extending laterally
from the downstream end of the stem and an annular peripheral region 132 that angles
back toward the seat 85 for abutting an inclined outer surface 133 of the flange.
The angling of the annular peripheral region 132 from the circular region 131 increases
the resistance of the flap 127 to deformation in response to air pressure change.
[0033] The exhalation or disc valve 87 on the other hand, has relatively little resistance
to deformation. The disc valve 87 is a circle of flexible material having a central
opening 134 by which it is held to a knob 136 of the valve seat by a washer 135. When
held at its center against the seat 85, the peripheral regions of the disc valve 87
press against the rim of the flange 124 giving the disc valve a convex-concave configuration.
The disc valve 87 deforms outwardly with relatively little resistance in response
to the pressure of exhaled air.
[0034] The preferred scrubber 30 is a combination lithium hydroxide-molecular sieve scrubber.
As hereinabove described, carbon dioxide reacts with solid lithium hydroxide to form
either lithium bicarbonate or lithium carbonate. The molecular sieve of porous material,
e.g. a form of zeolite, removes water particles, hydrocarbons and other chemical waste
by-products of respiration.
[0035] The scrubber 30 (FIG.8) is designed to maximize contact of the scrubbing material
and for replacement of a charge 94 of scrubbing material whereby the scrubber can
be refurbished. The scrubber 30 comprises the generally cylindrical cannister 52 having
a non-removable cover 88 at its outlet end and an optionally removable cover 90 at
its inlet end that allows for replacement of the charge 94 of scrubbing material.
Generally, the flow of exhausted air is through the inlet port 28, through the cover
90, into a region 92, through the charge 94 of scrubbing material, and out through
the axially disposed outlet port 32 of the non removable cover 88. Interior of the
ports 28, 32 at each end is a fine mesh metal screen 97 which filters out larger particles
and a layer 98 of filtering material, e.g. glass wool, to collect fine dust particles.
[0036] The end molecular sieve layer 56 collects water, hydrocarbons and other impurities
from the exhaled air. In particular, the first upper layer 56 prevents the continual
contamination of the breathing air. The lower layer 60 of molecular sieve material
traps additional impurities as noted above and particularly water, lest water tend
to clog the filter screens 98. Respiratory impurities are substantially removed by
the lithium hydroxide and the molecular sieve material and the total effect of passage
through the scrubber 30 is purified, heated carbon dioxide depleted air.
[0037] Because heated air becomes uncomfortable to breathe, particularly under the conditions
where the emergency apparatus might be used, the exterior of the cannister 52 which
is in contact with the, presumably cooler, ambient atmosphere is coated with a radiation
material 54 to reject heat. The air from the scrubber 30 enters the air bag 12 which
has a large surface area in contact with the cooling ambient air and is mixed therein
with expanding cooler oxygen from the oxygen bottle 14. Oxygen-replenished air flows
to the mouthpiece 22 through the inhalation conduit 18 bypassing the heat producing
scrubber 30. The combined effect of the measures taken to dissipate the scrubber produced
heat is to maintain the air which the user inhales below about 115°F, a temperature
at which the user can breath in reasonable comfort.
[0038] The shell 36 of the case 34 includes the substantially rectangular back 38 wall and
side walls 106 extending outward therefrom. The cover 40 (Fig. 4) has a similar shape
having a rectangular outer wall 108 and side walls 110 extending therefrom for peripheral
mating with the side walls of the shell. Latches 112 hold the cover 40 to the shell
36 and the sealing gasket 114 or other sealing means is interposed between the shell
and cover for sealing the interior region 44. The cover 40 is preferably deeper than
the shell 36.
[0039] The case 34 provides a region 44 (Fig. 4) of sufficient volume for containing the
breathing apparatus. The breathing bag 12, oxygen bottle 14, the valve unit 76 and
the scrubber 30 are each attached by straps, brackets or the like to the interior
surfaces of the shell 36. The case 34 is packed with the mouthpiece 22, the conduits
and the folded air bag 12 packed loosely therein. In a well packed case, the loose
members are disposed in the spaces between the secured members to afford a substantially
complete view of the apparatus therewithin.
[0040] The apparatus 10 may be stored for extended periods of time in areas which provide
for easy access by the user in times of emergency. Such areas, e.g., a mine, often
contain foul, dirty atmosphere, and from time to time, the apparatus in the sealed
case 34 is transported to a new work area. The hermetically sealed case 34 protects
the apparatus against dirt, pollutants and damage caused by impact during periods
of non use. While emergency breathing apparatus is commonly stored and imported in
metal cases, it is found that several advantages accrue from encasing the apparatus
in a strong durable and transparent material such as a polycarbonate.
[0041] Hygroscopic material, e.g., cupric sulphate, which changes color as it collects moisture,
may be sealed within the case 34. A loose packet 115 (Fig. 4) of hygroscopic material
for visual observation may be stored in the case. While color change is generally
indicative of a broken seal, in very dry atmospheres, a broken seal may not result
in sufficient pick-up of water vapor to effect a noticeable color change. In a transparent
case 34, the collection of dust and moisture within the case is an alternative indication
of a broken seal. The secondary indicia of the integrity of the seal obviates the
need to test stored units by submerging them in water.
[0042] If the cover 40 and/or the shell 36 is formed of transparent material, the pressure
gauge 74 on the oxygen line 16 need not extend through the wall of the case 34 but
may be read through the sealed case to ascertain the supply of oxygen. Furthermore,
disrepair of the apparatus can be observed without breaking the seal. Whereas one
might when needed open a metal case with its seal intact only to find a hose which
has become disconnected through jarring of the case making the unit non-serviceable.
Such obvious malfunctions can be easily detected by visual inspection through the
transparent case.
[0043] The weight of a polymeric shell 36 and cover 40 may be less than about one pound.
The combined use of a polymeric case 34 and a wound fiber glass, aluminum lined oxygen
container 14 may reduce the weight of the unit 10 by two pounds or more. Units 10,
particularly provided for respiratory patients, may be sealed in a hinged case to
be opened and later closed to reestablish the hermetic seal thus preventing exhaustion
of scrubbing material between periods of intermittent use.
[0044] It has been found that with heavy exertion, and heavy useage of the system for a
prolonged period of about an hour that the carbon dioxide level being inhaled begins
to rise to a level considered to be too high, e.g. about 1.5 percent by volume even
though there is enough lithium hydroxide in the scrubber 30 to last for one and a
half hours. Because the lithium hydroxide does not appear to be totally expended,
it does not appear necessary to increase the size of the scrubber 30 with attendant
cost increase and weight increase.
[0045] Instead, and in accordance with the invention, means have provided to increase the
residence time or the transit time of the gas being exposed to the scrubber 30 while
retaining substantially the same size for the scrubber 30 to maintain the carbon dioxide
at acceptable levels even after one hour of heavy useage of the apparatus. This is
achieved in the embodiment of the invention, illustrated in FIGURES 10 and 11 by substituting
an air bag 226 for the exhalation conduit 26 so that a larger volume of exhaled air,
e.g. about 2 liters, is present and exposed for a longer period of time to the lithium
oxide in the scrubber 30. More specifically, the collapsible air bag 226 of the same
material as the air bag 12 is connected at one end to exhalation port 24 of the mouthpiece
and at the other end to the inlet port 28 of the scrubber 30. When the user exhales,
the second air bag 226 will expand toward its full capacity of two liters to store
air therein in contrast to the same exhalation breath that would have driven most
of the exhaled breath through the exhalation conduit 26 which holds a very substantially
smaller volume than that of the second air bag. With the conduit 26 of the apparatus
of FIGURES 1-9, most of the exhaled air flowed quickly through the conduit 26 and
through the scrubber 30 to the air bag 15. As will be explained in connection with
FIGURES 12 and 13, exhaled air stays in air bag 226 until the next inhalation and
this provides increased transit time and reduced flow rate through the scrubber resulting
in a longer exposure of the carbon dioxide to the lithium hydroxide and a keeping
of the carbon dioxide level below 1.5 percent for a substantially longer period than
one hour. It is preferred that air bag 12 be made smaller, e.g. to hold about 3 or
4 liters rather than 5 liters used for the bag 12 in the embodiments of FIGURES 1-9.
Thus, the additional two liters in the bag 226 will pull from the bag 226 and through
the scrubber 30 as the smaller bag 12 is being exhausted during an inhalation cycle.
[0046] Referring now to FIGURE 12, there is a diagrammatic illustration of volume and pressure
of the air flow during inhalation and exhalation time periods. As measured at the
mouthpiece, the exhalation volume shown by the solid line curve 200 rises from about
zero to a peak volume at point 201 on the curve 200 while the pressure is rising in
a generally similar manner as shown by the dotted line curve 205 which has a peak
206 for the peak pressure.
[0047] At the mouthpiece, the inhalation cycles, shown on the negative side of a zero pressure
line begins slowly and increases as shown by the dotted curved line section to a negative
pressure that is greater in value than the positive pressure during exhalation. The
volume of scrubbed air drawn in through the mouthpiece from the bags 12 and 226 is
indicated by the curved line segment 214. The inhalation and exhalation curves may
be thought of generally sinusoidal.
[0048] FIGURE 13 is a diagrammatic illustration of the carbon dioxide concentration (or
level )by volume in the air being exhaled and inhaled. With the old system, during
exhalation, the carbon dioxide present in exhalation has little carbon dioxide therein
and as the exhalation continues the exhalation becomes richer in carbon dioxide. Thus,
carbon dioxide level rises from about zero at the beginning of exhalation to about
7 percent at the end of exhalation as shown by the curve 230 in FIGURE 13. At the
end of exhalation, the percentage of carbon dioxide terminates abruptly until the
next exhalation. Another dotted line 232, shows the carbon dioxide level at the inlet
port to the scrubber 30. With about one-half of the air of the exhalation flowing
into the scrubber, the percent of carbon dioxide will rise to about one-half of that
for curve 230, viz. about 3 or 3-1/2 percent as represented by the dotted line curve
232 in FIG. 13. With the second bag, the scrubbing action continues during the subsequent
inhalation and the air pulled from the bag 226 begins at 3-1/2 percent and drops as
it is scrubbed to zero percent carbon dioxide, as shown by the dotted line 234.
[0049] The user, e.g., a miner, should check his unit 10 daily for the integrity of protective
adhesive seals which are placed over the junction of the shell 36 and cover 40, for
change of color of the moisture indicator 115 within the case 34, for dust or moisture
within the case, the pressure of oxygen within the cylinder 14, as read by the gauge
74, and the condition of the apparatus within the case 34. In times of emergency,
the user breaks the seal and removes the cover 40. He dons the unit 10 by placing
the harness 42 over his neck and body harness around his body and quickly turns the
knob 47 opening the on-off valve 46 thereby inflating the air bag 12. To limit inhalation
to his mouth, he clamps a nose clip 119 to his nostrils. Preferably the nose clip
is loosely attached closely adjacent to the mouthpiece for ready availability. He
inserts the flange 82 of the mouthpiece 22 and grips the bits 84 with his teeth, and
inhales a breath of substantially pure oxygen. Thereafter the user makes any necessary
further adjustments in his harness 42 and continues to breathe through the mouthpiece
22 until the emergency has passed. Where possible, the user may aid in his own rescue,
his arms being free to take the steps necessary to extricate himself. Under heavy
exertion, the supply of oxygen is sufficient to last more than a full hour. Also,
with second air bag the carbon dioxide level may be kept low, i.e. below 1.5 percent,
even with heavy exertion by the user. If the situation precludes self extrication,
the user should remain as passive as possible to minimize his oxygen intake, and if
fully passive, may extend the life of the oxygen supply to upwards of six hours. If
the area is ventilated, albeit poorly, the user may further prolong the life of his
oxygen supply by intermittently relying on the ambient atmosphere and periodically
turning on the on-off valve 46 and inhaling from his unit 10.
[0050] In accordance with a further aspect of the invention, the transparent plastic case
may be made with anti-static properities to reduce the liklihood charge of static
electricity being accumulated on the case and causing a subsequent spark discharge.
To this end, it is preferred to add an anti-static additive to the plastic being molded
into the cover so that ultimate cover is more electrically conductive and less of
an electrical insulator on to which static electricity may collect and build.
[0051] All of the components of the apparatus are reusable. The oxygen bottle 12 is replenishable
through the inlet fitting 50 attachable to an exterior source of pressurized oxygen.
The scrubber 30 is rejuvenated merely by removing for replacement or by removing the
cover 90 and replacing the charge 94 of filtering material. Reusability is particularly
advantageous for patients subject to repetitive short term needs over a long period
of time. After exhaustion of a supply of oxygen, the unit 10 is returned to the manufacturer's
representative for service including oxgyen charging, scrubbing charge replacement
and case resealing. By providing substantially completely reusable equipment, the
cost to the consumer is kept down. The cost is further minimized by the user controlled
on-off valve 46 which permits intermittent use of the apparatus over extended periods
between recharging.
[0052] While the invention has been described in terms of a preferred embodiment, modifications
obvious to one with ordinary skill in the art may be made without departing from the
scope of the invention. For example, while the carbon dioxide scrubber has been described
in terms of a lithium hydroxide scrubber, other substances are known which react with
air-carried carbon dioxide, and scrubber charges utilizing other substances may be
used.
[0053] Various features of the invention are set forth in the following claims.
1. A portable emergency breathing apparatus comprising: a carrying means for said
apparatus, a high pressure container for containing a supply of oxygen, a demand regulator
means for controlling the flow of oxygen from said container in accordance with the
demands of the user, an air bag for containing a supply of breathable air and for
receiving oxygen from said container, scrubbing means for scrubbing carbon dioxide
from the exhaled air from the user and connected to said air bag to return scrubbed
air to said breathing bag, mouthpiece means connected to said breathing bag to allow
the user to intake air therefrom and connected to said scrubbing means to deliver
exhaled air thereto, and valve means operable by the user to start and to stop the
flow of oxygen from said container in accordance with the needs of the user.
2. An apparatus in accordance with Claim 1 in which a conduit means for carrying air
to said mouthpiece means bypasses said scrubbing means to deliver air directly from
said breathing bag to said mouthpiece means without passing through said scrubbing
means.
3. An apparatus in accordance with claim 1 or claim 2 which said carrying means comprises
a hermetically sealed case of transparent plastic.
4. An apparatus in accordance with any of claims 1 to 3 in which said high pressure
container is formed with a wound strengthening member of a non-metalic synthetic material
to hold oxygen at high pressures.
5. An apparatus in accordance with any of claims 1 to 4 in which said high pressure
container is provided with means for connection to a charging device for refilling
the container for reuse.
6. An apparatus in accordance with any of claims 1 to 5 in which said scrubbing means
includes a metal container having a carbon dioxide reactive material therein and in
which said metal container is configured to provide heat radiation to transmit the
heat being generated during the carbon dioxide reaction.
7. A portable emergency breathing apparatus comprising: carrying means for said apparatus
including a sealed case, a high pressure container for containing oxygen gas under
high pressure, an air bag connected to said container for receiving oxygen therefrom,
a mouthpiece means for insertion in the mouth of the user and for connection to said
air bag for receiving air from said air bag, and scrubbing means connected to said
mouthpiece for receiving exhaled air and for removing carbon dioxide therefrom for
reuse by the user, said scrubbing means including a layer of molecular sieve material
for purifying the exhaled air which may contain a considerable amount of hydrocarbons
initially during initial use, reaction material for reacting with the carbon dioxide,
and another layer of molecular sieve material following the carbon dioxide reactive
material.
8. An apparatus in accordance with Claim 7 in which said molecular sieve comprises
a zeolite material and said carbon dioxide reactive material comprises lithium hydroxide.
9. An apparatus in accordance with claim 7 or claim 8 which said scrubbing means includes
a metal cannister exposed to radiate heat therefrom.
10. In combination, emergency breathing apparatus and a case therefore, said breathing
apparatus comprising an air bag for containing a supply of breathable air, a high
pressure oxygen container formed of a metal and non-metalic synthetic material in
fluid communication with said air bag to deliver oxygen thereto, an inhalation means
connected to said air bag and an exhalation means connected to said scrubbing means,
said inhalation means having a one-way valve which opens when the user inhales and
closes when the user exhales, said exhalation means having a one-way valve which opens
when the user exhales and closes when the user inhales, said case including a shell
formed of a polymeric material and means to attach said breathing apparatus thereto,
a cover formed of a polymeric material, and sealing means interposed between said
shell and said cover for maintaining a hermetically sealed region around said breathing
apparatus prior to use.
11. A combination in accordance with Claim 10 wherein at least one of said shell and
said cover are formed of a transparent polymeric material.
12. A combination in accordance with Claim 11 wherein said polymer is polycarbonate.
13. A combination in accordance with any of claims 10 to 12 wherein said oxygen container
is provided with means for refilling the container for reuse.
14. A combination in accordance with any of claims 10 to 13 wherein said scrubbing
means comprises a cannister and a charge of carbon dioxide reactive material contained
therein, said cannister having a coating of radiation material to transfer heat from
the exterior of said cannister.
15. Emergency breathing apparatus comprising an air bag for containing a supply of
breathable air, an oxygen container and a conduit connecting the same to said air
bag, a mouthpiece means having an inhalation valve means and an exhalation valve means,
said inhalation valve means having a valve which opens when the user inhales and closes
when the user exhales, said exhalation valve means having a valve which opens when
the user exhales and closes when the user inhales, an inhalation conduit connecting
said air bag to said inhalation valve means, scrubbing means for removing carbon dioxde
from a mixture of gases, said scrubbing means having a cannister, a charge of carbon
dioxide reactive material contained therein, an inlet port and an outlet port, an
exhalation conduit connecting said exhalation valve means to said inlet port of said
scrubbing means, and a return conduit connecting said outlet port of said scrubbing
means to said air bag.
16. Apparatus in accordance with Claim 17 wherein said inhalation valve provides greater
resistance to breathing than said exhalation valve.
17. Apparatus in accordance with Claim 16 wherein said inhalation valve is an umbrella valve and said exhalation valve is a
disc valve.
18. A portable emergency breathing apparatus comprising: a carrying means for said
apparatus, a high pressure container for containing a supply of oxygen, a first air
bag for containing a supply of breathable air and for receiving oxygen from said container,
a scrubber for scrubbing carbon dioxide from the exhaled air from the user and connected
to said air bag to return scrubbed air to said breathing bag, a mouthpiece connected
to said breathing bag to allow the user to intake air therefrom and connected to the
scrubber to deliver exhaled air thereto, and a second air bag connected to the mouthpiece
for receiving exhaled air containing carbon dioxide from the mouthpiece and connected
to the scrubber to deliver air thereto to increase the transit time of the exhaled
air through the scrubber.
19. An apparatus in accordance with Claim 18 in which the air bag is expandable and
collapsible for holding an expanded volume of about two liters of air.
20. A portable emergency breathing apparatus comprising: a carrying means for said
apparatus, a high pressure container for containing a supply of oxygen, an air bag
for containing a supply of breathable air and for receiving oxygen from said container,
scrubbing means for scrubbing carbon dioxide from the exhaled air from the user and
connected to said air bag to return scrubbed air to said breathing bag, mouthpiece
means connected to said breathing bag to allow the user to intake air therefrom and
connected to said scrubbing means to deliver exhaled air thereto, the container being
a composite container having a metal layer and a wound outer layer to hold the oxygen
at a predetermined pressure.
21. An apparatus in accordance with Claim 20 in which said carrying means comprises
a plastic case for holding the apparatus and antistatic means for the plastic case
to reduce buildup of static electrical charges on the plastic case.