Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
In the normal breathing process, inhaled air becomes warmed
and humidified as it passes through the nasal, tracheal and bronchial
passages. This basic body function protects the delicate membranes in the
lS lungs, but may not be sufficiently effective in heavy or rapid breathing of very
cold dry air. During exhalation, some heat and moisture is returned to
the walls of the breathing passages, but most of the heat energy and moisture
is lost in the exhaled gases.
At rest and at a comfortable room temperature, the energy loss
20 is on the order of 1 Kcal per hour, and is easily compensated by normal
body functions. However, as an example, at a temperature of -30C and
at an altitude of 5, S00 meters, with a low humidity and at a moderate
working rate of 60 breaths per minute, averaging about 2 liters per breath,
the loss would be about 230 Kcal and 250 grams of water per hour. This is
25 a significant portion of the body's energy output and the mere use of warm
clothing may not be sufficient to retain a desirable amount of the energy.
Also, since thirst response is suppressed by extreme cold, dessication
could become a problem.
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Various techniques have been developed for heating and humidify-
ing breathing gas, but are usually complex and heavy. Thermal heaters re-
quire power sources, and are not particularly efficient in their use of energy,
in a dry atmospheric environment, a humidifier must contain stored water in
some form and is thus heavy and bulky. For convenience and reliability such
apparatus should be simple, compact and require a minimum of storable energy
producing medium.
The apparatus described in this invention is adaptable to breath-
ing masks, mouthpieces and the like used in underwater or atmospheric environ- -
ments. Typical uses include scuba diving, mountain climbing, operations in
arctic or severe winter conditions or cold survival stiuation, and in
aviation and space operations. Generally the uses include any conditions ; :
under which air or breathing gas must be used at extremes of cold and low
humidity.
The invention provides a heater and humidifier for adding heat and
moisture in a controlled amount to a breathing gas, such as air, for use in -
a human breathing apparatus, comprising: means for providing a supply of
hydrogen and oxygen breathing gas with the hydrogen being less than three - -
percent by volume of the combined mixture, a heater unit having inlet means -
for connection to said gas supply means and an outlet for connection to a -
breathing utilization element, valve means coupled to said heater unit for :
controlling the flow of hydrogen and breathing gas, and catalyst means in -
said heater unit for providing combustion of the hydrogen in the breathing
gas adding heat and moisture to the gas passing out through the breathing
element.
The apparatus utilizes a source of hydrogen, preferably in its
gaseous form for convenience of storage and utilization. The amount used is -
very small and a small high pressure cylinder will hold sufficîent hydrogen
for prolonged use. In the simplest form of the apparatus, the hydrogen is
pre-mixed in suitable proportions with the air or breathing gas, in a pres-
surized container. The heater is installed directly in the line from the
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supply to the breathing outlet, such as a mouthpiece or mask and is a
catalytic type to avoid the need for a power source. Suitable catalysts
include metals or metal oxides of platinum, palladium, vanadium, chro-
mium, copper, manganese, cobalt and nickel. mese may be coated or
supported on carriers such as alumina, magnesia, silica gel, asbestos,
diatomaceous earth, or metallic wires such as in screen material.
As the hydrogen containing breathing gas passes over the
catalyst~ the hydrogen is combusted and heats the gas. In addition,
the hydrogen combines with oxygen in the breathing gas and produces water --
vapor to humidify the gas. As long as the amount of hydrogen is kept
below 3% of the total gas content, there is no danger of explosion and
the combustion is easily controlled. The amount is more than ample to
provide the energy required under all reasonable conditions for which -
the apparatus is designed.
In other forms, primarily for atmospheric use, the hydrogen is
stored in a container and is injected in a controlled amount into the
flew of breathing gas. me hydrogen is injected into catalytic material -
or adjacen~tto a catalytic or other heating element. For convenience,
the structural heating unit may be incorposated in the breathing mask
itself. Flow is controlled by a valve which is responsible to the con- ~-
dition of the breathing gas, such as a demand valve operated by the --
breathing action, or by temperature sensing means which maintains a
stable heating condition.
T~e objects and advantages of the invention will be apparent
in the following detailed description, taken in conjunction with the -
accompanying drawings, in which
Figure 1 illustrates the system in its simple form, ~ith portions
of the heating unit cut away.
Figure 2 is a side elevation view, partially cut away, of a
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11~41~tj7
breathing mask incorporating a heating unit with a temperature
controlled hydrogen flow control valve.
Figure 3 is a side elevation view of a similar breathing ~ -
mask, but with a demand type control valve in the heating unit.
Figure 4 is a graph showing the relationship of hydrogen
input to temperature.
Figure S is a graph showing the relationship of hydrogen
input to humidity. --
In the simple form illustrated in Figure 1, hydrogen is --
premixed with breathing gas and stored in a pEesurized cylinder or
container 10 having a flow control valve or regulator 12. A~s~pply
hose 14 leads from valve 12 to the inlet 16 of a heater unit 18
further hose 21 leads from the outlet 20 of heater unit 18 to ~ -
a breathing utilization element, illustrated as a mouthpiece 22.
me mouthpiece has a demand type valve 24, which passes~breathing
gas on demand as the user draws a breath. me container
10, regulator 12, mouthpiece 22 and valve 24 are standard items used in
scuba diving equipment.
Heater unit 18 comprises a simple cylindrical canister 26, with
tubular inlet and outlet 16 and 20 for attachment of the hoses in any
approved manner. The canister 26 contains a catalytic material 28 in
- granulated or pelletized from which will permit passage of the gas. Screens
30, or similar perforated retainers at opposite ends of the canister prevent
the catalytic material 28 from passing through the inlet or outlet. One
suitable material for the catalyst is alumina pellets coated with 0. 5%
platinum, the pellets being about 3 mm in diameter. Other catalytic m~terials
are listed above and various combinations may be used.
In one particular system, about 10-15 grams of platinum coated -
alumina pellets were used and required about 15-20 minutes to reach a
stable operating temperature. Initial warm up can be accelerated by exter~l
heating, the amount of heat required being small, such as obtained by
holding the canister under the user's arm. With the hydrogen premixed in the
breathing gas, the temperature increase obtained is predetermined, but
can be controlled to some extent by addition or removal of insulation 32
around canister 26.
The amount of hydrogen in the breathing gas is small and non- - -
explosive, the maximum desired amount being about 3%. As illustrated
in the graph in Figure 4, the addition of 0.1% of hydrogen to the basic
breathing gas will produce an ideal temperature increase of 7. 8C, or
78C for a 1% addition of hydrogen. The actual temperature increase will ~ :
depend on 8ystem efficiency and control of heat losses. From the graph
of Figure 5, it can be seen that the addition of 1% hydrogen causes a nominal
introduction of 1% in water vapor.
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The temperature change is constant at any ambient pressure and is
thus essentially predictable at any altitude on land or any depth in the ocean.
However, the humidity change is dependent on temperature and pressue
according to the equation:
%H2O/100 x Pa
r = x 100
Pv
where r is the relative humidity
Pa is the ambient pressure of the gas being breathed in mm of
mercury
Pv is the vapor pressure of water at the existing gas temperature.
10 At sea level and room temperature, a 0.1% increase in water vapor is
equivalent to approximately 3% increase in relative humidity. From the
s equation, this becomes about 1. 5% at 5, 500 meters altitude and about 6%~, at twice atmospheric pressure, as under water. Using the same hydrogen
to breathing gas ratio, a diver would thus breathe air more saturated in
15 moisture than a mountain climber. - -
In producing the water vapor, the hydrogen consumes half of its
amount of oxygen. ~n air, or in atmospheric pressure ranges with an oxygen
content of up to 20% in the breathing gas, this would be inconsequential. For
deep sea diving at high pressures, however, the oxygen content of the breathing ~ -
20 gas is quite low, on the order of 1 %. A diver using 0. 5% of hydrogen in thebreathing gas would thus have to add 0. 25% of oxygen to the basic mixture
for combination with the hydrogen. -~
As an example of the action of the system in air, at a temperature
of -30C and a relative humidity of 10%, with a breathing rate of 60 breaths
25 per minute at an average of 1. 5 liters per breath, the loss is about 190
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grams of water and 215 Kcal of ene rgy per hour. To raise the temperature
of the breathing air by 60C, or to +30C, would require the addition of 0. 77%
hydrogen. This would also add 0. 77% water vapor to the breathing air,
which results in the addition of 34 grams of water and 105 Kcal of heat
5 energy per hour. About one liter of hydrogen at 2500 psi would supply this
energy increase for about 10 hours. It c~n be seen that a large portion of
the energy loss is replaced and the loss can be decreased by adding more
hydrogen, up to 3%, to the breathing gas. The limitation is the maximum
temperature of gas which can be comfortably breathed. It should be noted
10 that the heater unit could be extended and incorporated into a portion of
a wet suit or clothing to obtain the benefit of the heat produced for body
heating.
When control of the hydrogen is required, instead of a set pre-mixed
amount, the arrangement of Figure 2 may be used. The apparatus as shown
i8 designed for use in air and includes a container 10 with a regulator 12
and supply hose 14. In this instance the container holds only hydrogen and
can be quite small for ease of portability.
The heater unit 34 is attached directly to a breathing outlet, illustrated -
as a face mask 36 with securing straps 38. The face mask is provided with
20 a diaphragm outlet valve 40 of conventional type to release exhaled air.
Other types of outlet valves may be equally suitable, depending on the ~ - -
overall mask design and purpose. ; -
Heater unit 34 comprises a canister 42 having a diaphragm type
inlet valve 44, or similar one way valve, in the closed end 46. The other
or outlet end 48 iB open and fits into face mask 36. A baffle plate 50 is ~
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inset from the open end 48 and has perforations 52 for breathing gas passage.
The enclosed chamber between closed end 46 and baffle plate 50 contains the
pelletized catalytic material 54. Hose 14 is connected to the hydrogen source
inlet 56 of a valve unit 58, attached to or incorporated into the canister 42,
and enclosing a hydrogen inlet 59 in the canister, opposite source inlet 56.
A manifold tube 60 extends from inlet 59 into the canister and has per-
forations 62 to distribute hydrogen across the full width of the canister.
In the valve unit 58 is an actuating arm 64 pivotally mounted on a
bracket 66. On one end of arm 64 are back to back valve elements 68 and
70, valve element 68 being positioned to close inlet 56 and a valve element
70 being positioned to close the opening to manifold tube 60. The other
end of arm 64 is connected by a link 72 to a temperature sensing element 74,
mounted on bafne plate 50, or on some other suitable support in the canister.
The temperature sensing element is preferably a mechanically actuating type,
s uch as a bimetallic strip or coil which will apply a motion to line 72 as
the temperature changes the arrangement being well known. The incoming
hydrogen flow is small and the pressure, controlled by regulator 12, will
normally be quite low, so valve sealing is not a problem. Link 72 passes
through a seal 76 to prevent hydrogen leakage directly into the face mask.
Temperature sensing element 74 is set to cause valve element 70 to close
manifold tube 60 when the breathing gas exceeds a predetermined comfortable
temperature. The temperature actuated control thus provides a safety ;
factor in the operation of the apparatus. At a predetermined low ternperature
valve 68 close~ inlet 56 to shut off hydrogen flow and protect against a
malfunction of the catalyst. Since this means that the hydrogen inlet will
be closed when the unit is cold, a starting button 78 is provi~ed to open the
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inlet and initiate hydrogen flow. Button 78 engages arm 64 so that the
holding action of temperature sensing element 74 can be overcome to open
valve element 68. The head 80 of button 78 acts as a stop against valve
unit 58 to limit the movement of arm 64, so that valve element 70 is not
5 inadvertently closed when starting and that both inlets 56 and 59 are
simultaneously open. A small boot seal 82 over button 78 prevents hydrogen
leakage. The valve configuration and operation as illustrated should be
considered as exemplary, and other arrangements may be used to obtain -
equivalent action.
In operation, each inhaled breath draws air through inlet valve 44 and
through canister 42. Hydrogen emitted from manifold tube 60 reacts in the -catalytic material 54 and heats the air, while combining with oxygen in the
air to provide moisture. The burst of heat occurring with each intake of ~- -
breath is moderated by the heat sink capacity of the catalytic material
15 and the output is substantially constant. If the temperature be~mes too highJthe temperature sensing element 74 causes valve 70 to close and shut off the
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hydrogen input, so that an explosive mixture cannot build up. The heat
remaining in the body of catalytic material warms the incoming air until the - - -
temperature drops to a safe operating level. It should be noted that, while - - -
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20 the apparatus is illustrated for use in air, which is drawn directly through
inlet valve 44, any suitable source of breathing gas can be connected to the - ~
inlet of the canister if required. - ~ -
In an alternative arrangement, illustrated in Figure 3, hydrogen
flow is controlled by a demand type device actuated by the breathing action.
25 The face mask 36 is as described above and hydrogen is supplLed through a
ho~e 14, as in Figure 2.
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- In this configuration the heater unit 84 comprises a canister 86
having an air inlet 88 at the outer end, and an inlet valve 90 in the open
end 92 which fits into mask 36. Air from inlet 88 passes through a venturi
94 having a reduced throat portion 96, to produce a pressure drop in the air
5 flow. In the throat portion 96 is a flexible diaphragm 98, which is drawn
into the throat by the pressure drop occuring at each intake of breath.
Attached to the canister 86 is a valve unit 100 to which supply hose
14 is connected, a manifold tube 102 extending from the valve unit across the
canister. Hydrogen flow into the manifold tube is controlled by a needle valve
10 104 mounted on one end of an airm 106, and seating in the hydrogen inlet 107. ~ -
The other end of arm 106 is connected by a link 108 to diaghragm 98. The -
arm passes througharesilient wall 110 also serving as a pivot for arm 106
but any other suitable pivotal support may be used.
Each intake of breath pulls diaphragm 96 in and causes needle valve
lS 104 to be opened, releasing hydrogen into the manifold tube 102. Adjacent
the manifold tube is a catalytic element 112, shown as a wire screen, which
would be coated with catalytic material. Other type of catalyst or ignition
means may be used to initiate the hydrogen combustion. The hydrogen is
thus supplied on demand by the breathing action, and the amount can be
20 controlled by calibration of the needle valve. Since the hydrogen content is
precisely controlled in accordance with the breathing action, the temperature
can be properly balanced and there is no need for any heat sink effect to
smooth out the heating action. It should be understood that temperature
controlled safety means, as in Figure 2, may be used in conjunction with the
25 pressure actuated valve of Figure 3.
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As illustrated, the hydrogen is stored in a cylinder under pressure,
but could be obtained from other sources such as metal hydrides, or from
various chemical reactions where circumstances permit. In some
instances light hydrocarbons could be used. The lightest hydrocarbons,
such as methane and ethane give off water and carbon dioxide when burned
in air, and produce sufficient heat at low concentrations so that the amount
of carbon dioxide added to the breathing air is not harmful at low
atmospheric pressures.
It will be evident that the controlled hydrogen combustion means can
be incorporated in a variety of breathing apparatus, to obtain any required
degree of heating, with the added advantage of moisturizing the breathing
mixture. The structure is adaptable to many existing systems and installations
and is simple to operate and maintain.
Having described our invention, we now claim:
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