Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
I
EMERGENCY OXYGEN SUPPLY SYSTEM
Field
The present invention relates to an emergency oxygen supply system. Emergency
oxygen supply systems are provided in aircraft, to enable passengers and crew
to breath
without loss of consciousness in event of loss of cabin pressure at elevated
altitude.
Context
In the words of Wikipedia, there are two systems that are typically found on
aircraft:
- A gaseous manifold system, which connects all oxygen masks to a central
oxygen
supply, usually in the cargo hold area. Pulling down on one oxygen mask starts
the oxygen
supply for that mask only. The entire system can usually be reset in the
cockpit or in some
other location in the aircraft.
- ______________________________________________________________________ A
chemical oxygen generator system connected to all masks in the compai
anent.
Pulling down on one oxygen mask removes the firing pin of the generator
igniting a mixture
of sodium chlorate and iron powder, opening the oxygen supply for all the
masks in the
compartment. Oxygen production cannot be shut off once a mask is pulled, and
oxygen
production typically lasts at least 15 minutes. During the production of
oxygen, the
generator becomes extremely hot and should not be touched. A burning smell may
be noted
and cause alarm among passengers, but this smell is a normal part of the
chemical reaction.
This system can be found on the McDonnell Douglas MD-80 aircrafts, whose
system is
also unique in the fact that the face masks are clipped to the inside of the
compai intent door
and do not drop out and hang, by the oxygen tube, in front of the passengers.
In view of weight and heat generation, there is interest in replacing chemical
oxygen
generation systems with gaseous oxygen systems, albeit without the complexity
of a
central oxygen supply.
Self-Contained Breathing Apparatus is known, particularly in the form used
under-
water by divers as Self-Contained Underwater Breathing Apparatus ¨ hence the
acronym
SCUBA. Such apparatus releases air via a demand valve on breathing in by the
user and
provides all the air required for the user to breath, as is of course
necessary underwater, but
not in an aircraft at elevated altitude where the air is simply too thin.
It is known to release oxygen on breathing of ambient air for patients whose
breathing is inadequate to draw in sufficient air. Reduction of pressure in a
delivery tube,
due to breathing in, causes a regulator to release a pulse of oxygen per
inhalation from an
Date Recue/Date Received 2021-07-13
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intermediate reservoir into the delivery tube. Such a pulse regulator can be
electro-
mechanical or purely mechanical.
Summary
An electromechanically regulated, aircraft, pulse, emergency oxygen supply
system
has been proposed.
The object of the present invention is to provide a more economic, purely
mechanical, pulse, emergency oxygen supply system for aircraft.
According to the invention there is provided an emergency oxygen supply system
comprising: a source of compressed oxygen, means for releasing oxygen from the
source
in response to (in case of) a drop in air pressure, at least one oxygen mask,
a respective
mechanical breath-actuated valves for releasing a pulse of oxygen into the or
each mask
and a pressure reducer for releasing oxygen from the source into an
intermediate reservoir
upstream of the breath-actuated, pulse valves.
Normally the components of the system will be for aircraft use and housed in a
dedicated compartment in the base of luggage bins above passenger seating,
with means
for releasing the or each mask to a user in response to a drop in air
pressure. Whilst we
can envisage providing the breath-actuated pulse valve(s) in the compai __
anent, with a
pressure reducer and a respective intermediate reservoir upstream of each
mask's pulse
valve, with a tube to the mask downstream of the pulse valve; in the preferred
embodiment,
the or each pulse valve is arranged at the mask. In this arrangement, the
intermediate
reservoir or at least part of it is provided as the internalvolume of the
respective tube to the
or each mask.
The pressure reducer can be a single pressure regulator for supplying multiple
tubes
for multiple masks, or indeed a respective regulator for each tube. The or
each regulator
will normally be throttled to ensure that the amount of oxygen released as
each pulse is not
significantly augmented, during release of the oxygen in the tube as a pulse,
by flow through
the regulator prior to closure of the pulse valve for accumulation of the next
pulse in the
tube. Alternatively the pressure reducer can be a simple throttle supplying
multiple tubes,
or indeed a respective throttle for each tube, the throttle being sized to
increase the pressure
in the tube(s) to at least that appropriate to refill the tube during a normal
breathing period.
Whilst the source of oxygen will normally be a bottle or cylinder housed in a
compartment also housing the mask(s) ready for release, it can include a pipe
to the
compartment from a remote bottle or cylinder(s).
Date Recue/Date Received 2021-07-13
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This arrangement is preferred only in parts of the aircraft potentially
vulnerable to
an engine fan blade damage.
The source of compressed oxygen may contain compressed pure gaseous oxygen or
an oxygen rich mixture of gases.
In accordance with a particular preferred feature of the invention, a first
pulse
augmenter may be provided. In a possible embodiment, this comprises a
reservoir arranged
to be filled with oxygen for the first pulse and isolated thereafter by a shut
off valve actuated
by differential pressure resulting from release of the first pulse.
For instance, each first pulse augmenter comprises a throttle in a passage
from the
pressure regulator to the respective pulse valve, downstream of the throttle a
branch passage
leading to the augmenter reservoir arranged to fill prior to a first pulse
being released by
the pulse valve, a further passage leading from upstream of the throttle to
one side of a
augmenter diaphragm, the other side of the augmenter diaphragm being open to
the branch
passage, the diaphragm carrying an obturator arranged to engage with and close
an orifice
across the branch passage between intermediate the passage and the reservoir,
the obturator
being initially held out of the orifice by a spring so that, prior to a first
breath taken by a
user of the respective mask, the augmenter reservoir and the tube are filled
with oxygen via
the branch passage and, when the user takes the first breath, the pulse valve
allows oxygen
in the tube and the reservoir into the mask as an augmented first pulse, the
throttle generating
a build up of pressure on the further passage side of the diaphragm before the
pressure rises
in the branch passage causing a differential pressure across the diaphragm
causing it to move
with seating of the obturator in the orifice, the reservoir being then not
filled and not
available to augment subsequent oxygen pulses, the mechanism comprising a
mechanical
latch locking the obturator in the position closing the orifice during the
followings pulses.
As an optional feature of the invention, a barometric pulse compensation valve
may be provided. In a possible embodiment the oxygen reservoir has an
adjustable volume
and/or pressure depending upon the barometric pressure thus providing a
variable volume
pulse to the mask. This means that an altimetric sensing device may adjust the
pressure
and/or flow from pressure regulator 15 into tube 5.
This could be embodied by a reservoir that has its volume controlled by the
movement of a diaphragm which has one side connected to the barometric
pressure and
the other side linked to the oxygen reservoir and control by the reservoir
pressure and or
Date Recue/Date Received 2021-07-13
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a spring. A further refinement could link the barometric pressure to the
pressure regulator
to adjust the pressure of the oxygen supplied to the oxygen reservoir.
Also provided is an emergency oxygen supply system for aircraft comprising:
- a source of compressed oxygen;
- means for releasing oxygen from the source in case of a drop in air
pressure;
- an oxygen mask having a pair of non-return valves to the ambient
atmosphere, said pair of
non-return valves comprising an inhalation valve provided for allowing a user
to draw in the
mask ambient air, for inhalation with oxygen, and an exhalation valve provided
for allowing
exhalation from the mask to ambient;
- an oxygen supply tube supplying oxygen from the source to the oxygen mask;
- a mechanical breath-actuated valve for releasing successive pulses of
oxygen into the
mask; and
- a pressure reducer for releasing oxygen from the source into an
intermediate reservoir
upstream of the mechanical breath-actuated valve, the intermediate reservoir
or at least part
of the intermediate reservoir being provided as an internal volume of the
oxygen supply tube.
The intermediate reservoir determines how much oxygen is to be released at
each successive
pulse of oxygen. The mechanical breath-actuated valve is a "pulse valve" that
opens on
pressure reduction in the mask, induced by inhalation causing a pressure
differential across
the inhalation valve, the opening of the mechanical breath-actuated valve
allowing the
oxygen stored in the oxygen supply tube to be released as a pulse into the
mask and, on
release of the pulse, the mechanical breath-actuated valve closes again for
accumulation of
a fresh pulse's worth of oxygen in the oxygen supply tube. When the user takes
a breath at
which the mechanical breath-actuated valve is activated, a negative pressure
occurs in the
mask and produces a flow of oxygen that operates before the inhalation valve
opens; and
upon exhalation of the user, a positive pressure occurs in the mask and the
flow from
mechanical breath-actuated valve ceased as exhalation valve opens.
Brief description of the drawin2s
To help understanding of the invention, a specific and non limiting embodiment
thereof will now be described by way of example and with reference to the
accompanying
drawings, in which:
Figure 1 is a diagrammatic perspective view of an emergency oxygen supply
system
of the invention;
Date Recue/Date Received 2021-07-13
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Figure 2 is a side view of an oxygen cylinder and deployed mask of the system
of
Figure 1;
Figure 3 is cross-sectional view of the oxygen cylinder of Figure 1 and
Figure 4 is a view similar to Figure 3 of a first pulse augmenter.
Detailed description
Variants, examples and preferred embodiments of the invention are described
therein
below. Referring to the drawings, an emergency oxygen system compartment 1 has
an
oxygen cylinder 2 with a oxygen flow pressure reducer release valve 3. Housed
in the
compartment are a plurality of masks 4 having respective oxygen supply tubes
5.
A closure flap 6 is retained by a barometric latch 7 which can be a solenoid
released
latch, wired to a central barometric switch 8 applying power to and the
aircraft's solenoids
in the event of cabin pressure reduction. Release of the closure flap 6
releases the masks 4
for passengers to grasp and use.
Each mask 4 has a pair of conventional non-return valves 11, 12 to the ambient
atmosphere.
Inhalation valve 11 allows the user to draw in ambient air, for inhalation
with
oxygen as described below, whilst exhalation valve 12 allows exhalation to
ambient. In
accordance with the invention, the mask 4 also carries a pulse valve 14
connected to its
tube 5 and opening into the mask. The pulse valve 14 is of the type that opens
on pressure
reduction in the mask, induced by inhalation causing a pressure differential
across the
inhalation valve.
The mechanical breath-actuated valve may include has a housing including a gas
intake portion, an intermediate portion, and a gas outlet portion; a movable
valve stem
between the intake and intermediate portions, a spring biasing the stem
towards the closed
position; with the outlet portion having an exterior surface with a gas outlet
opening located
therein. That is to say, the mechanical breath-actuated valve allow passage of
oxygen into
the mask when relative negative pressure is sensed into the mask at the
downstream outlet
of said mechanical breath-actuated valve during inhalation. Oxygen contained
in a
reservoir portion of said mechanical breath-actuated valve is then allowed to
flow
through the downstream outlet of the valve. Thus a discrete volume of oxygen
in a form
of a pulse is provided by the mechanical breath-actuated valve into the mask
very rapidly
and before inhalation. The flow of oxygen in the mask terminates when the
reservoir
Date Recue/Date Received 2021-07-13
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portion of said mechanical breath-actuated valve is depleted. When this occurs
the
mechanical breath-actuated valve closes and the reservoir portion of said
mechanical
breath-actuated valve begins to refill. The negative pressure occurring when
the user
takes a breath at which the mechanical breath-actuated valve 14 is activated
produces a
flow of oxygen that operates before the inhalation valve opens. Upon
exhalation, positive
pressure in the mask occurs and flow from mechanical breath-actuated valve 14
has
already ceased as exhalation valve 12 opens.
For example, the mechanical breath-actuated (pulse) valve may be the type of
the
one disclosed in documents US20150040906A1.
Opening of this valve 14 allows the oxygen stored in the tube 5 to be released
as a
pulse into the mask 4. On release of the pulse, the pulse valve 14 closes
again for
accumulation of a fresh pulse ls- worth of oxygen in the tube 5. In this way,
the tube 5 acts
as a reservoir determining how much oxygen is to be released as each
successive pulse.
At the compartment end of each tube 5, a pressure reducer 15 is connected.
This
can be a pressure regulator or a simple throttle. It allows oxygen to flow
into the tube 5 to
a pressure such that, taking account of the volume of the tube 5, it acts as a
reservoir for
each pulse released by the pulse valve 14. The pressure downstream the
pressure
reducer 15 can be set between 2 bar and 10 bar with a preferred pressure
between
4 bar and 7 bar.
In case the tube 5 is connected to one mask 14, the tube 5 volume may
have a volume between 10 ml and 80 ml, with a preferred volume between 15 ml
and 50 ml, for supplying gas to one mask 14.
The tube(s) 5 may be flexible and made of PVC.
Upstream of the pressure regulators 15 is the oxygen release valve 3. This may
have a body 21 clamping a diaphragm 22 to a seat 23 in a mouth of the cylinder
2. The
body carries for example a spring loaded pin 24 held from piercing the
diaphragm 22 by a
withdrawable yoke 25. This is connected by a cord 26 to each of the masks 4 of
a length to
hold up the released masks 4 just short of the passengers needing to use it,
whereby grasping
of a mask 4 pulls the yoke 25 clear of the pin 24, releasing it to release
oxygen. The body
has a passageway 27 from the region of the pin's piercing end to a union 28 to
a pipe 29
leading oxygen to the pressure regulator 15.
The body also carries a spring loaded plunger 31, which bears on the middle of
the
diaphragm 22. The outer end of the plunger 31 is connected to a flag 32.
Should the pressure
Date Recue/Date Received 2021-07-13
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of the oxygen in the cylinder 2 drop through leakage, the plunger 3 deflects
the diaphragm
22 and this is witnessed by the flag 32.
The invention is not intended to be restricted to the details of the above
described
embodiment. For instance, the system could have only a single mask 4 for use
in a lavatory.
Further as shown in Figure 2, optional first pulse augmenters 41 can be
provided
downstream from the pressure regulator 15. Each oxygen supply tube 5 may have
a first
pulse augmenter 41. These can be provided in the compartment 1 at the feed
into the tube
5. Alternatively, they can be provided at the respective masks 4.
As shown in Figure 4, each first pulse augmenter 41 may have a throttle 42 in
a
passage 43 from the pressure regulator 15 to the respective pulse valve 14.
Downstream of
the throttle 42 a branch passage 44 leads to an augmenter reservoir 45
arranged to fill prior
to a first pulse being released by the pulse valve 14. A further passage 46
leads from
upstream of the throttle 42 to one side of a diaphragm 47. The other side of
the diaphragm
47 is open to the branch passage 44.
The diaphragm 47 carries a cone 48 arranged to engage with and close an
orifice 49
across the branch passage 44 between intermediate the passage 43 and the
reservoir 45.
Initially the cone 48 is help out of the orifice 49 by a spring latch 50.
In this state, prior to a first breath taken by a user of the respective mask
4, the
reservoir 45 and the tube 5 are filled with oxygen via the passage 44. When
the user takes
the first breath, the pulse valve 14 allows oxygen in the tube 5 and the
reservoir 45 into the
mask 4 as an augmented first pulse. The result, due to the throttle 42 is a
build up of
pressure on the further passage 43 side of the diaphragm 47 before the
pressure rises in the
branch passage 44. This causes a differential pressure across the diaphragm
47, causing it
to move with seating of the cone 48 in the orifice 49. The reservoir 45 is
then not filled and
is not available to augment subsequent oxygen pulses. The spring latch 50
comprises a U
shaped, spring clip 51 which engages as a detent in a groove 52 in backing
member of the
cone 48, with the diaphragm 47 captive between the cone 48 and the backing
member.
The free end 53 of the backing member is conical. When the differential
pressure displaces
the diaphragm 47, the clip 51 is held by an abutment 54 and passed in an over-
centre manner
over the ridge 55 between the groove and conical end 53. As soon as it has
passed over-
centre, the spring clip 51 acts on the conical end to keep the shut off valve
comprised by
the cone 48 and the orifice 49 closed. Thereafter as the supply tube 5 fills
for each successive
pulse, it is the volume of the tube which determines the amount of oxygen in
each pulse.
Date Recue/Date Received 2021-07-13
