Patent Description:
During cruise portions of flight, most commercial passenger aircraft operate at altitudes exceeding four thousand two hundred meters (fourteen thousand feet). At these altitudes, insufficient oxygen may be present in the ambient air to sustain human consciousness or life. Accordingly, cabins of the aircraft are pressurized, often to altitudes equating approximately two thousand four hundred meters (eight thousand feet). At such "cabin altitudes," sufficient oxygen normally will be present in ambient air to avoid hypoxia and thereby sustain human consciousness and life.

Loss of cabin pressurization when an aircraft is flying above, e.g., four thousand two hundred meters (fourteen thousand feet), therefore, creates risk of passengers (and crew) experiencing hypoxia. Aircraft hence typically are fitted with emergency oxygen systems configured to supply supplemental oxygen to passengers temporarily while an aircraft operator reduces the flight altitude of the aircraft. The systems include cup-shaped face masks connected to sources of oxygen via flexible tubing.

<CIT> to Cannon describes such an emergency oxygen system for use on-board aircraft. A pressure sensor is fitted to each mask and "generates a signal when a positive pressure is detected within the mask such as is caused by exhalation. " See Cannon, col. <NUM>, <NUM>. <NUM>-<NUM>. The detected exhalation causes a controller to open an inlet valve associated with the mask to allow a pre-selected volume of oxygen to flow into an associated reservoir bag. <NUM>-<NUM>. This pre-selected volume is then provided to the passenger at the beginning of the passenger's inhalation phase, supposedly for most efficient transfer of oxygen to the passenger's blood. <NUM>, <NUM>. <NUM>-<NUM>.

Clear, therefore, is that detection of a pressure change within a mask can be important for optimal functioning of certain emergency oxygen systems. Although systems of the Cannon patent apparently fit pressure sensors directly onto or within face masks, this approach exposes the sensors to contact with and actions of the passengers who, in chaotic emergency situations, may inadvertently damage the sensors or disrupt their operation. Resolution of this issue may occur by moving the pressure sensors upstream of the associated masks. However, doing so risks that the sensors may fail to detect respirations should the delivery tubes become blocked downstream of the sensors (i.e. between the sensors and the associated masks), as when moisture in the masks freezes, for example.

Otherwise, document <CIT> discloses an electronic control circuit for alleviating altitude sickness and oxygen supply device. The electronic control circuit includes an oxygen sensor installed in an oxygen supply channel, a breathing frequency sensor installed to the front of a head of a human body, and a microcontroller coupled to a control button, a flow proportion electromagnet, a bypass electromagnet and an air pump motor. The oxygen sensor and breathing frequency sensor detect analog signal and transmit the signal to the microcontroller after an analog-to-digital conversion, and an ON/OFF signal of the control button is transmitted to the microcontroller. The microcontroller has a flow control end coupled to a flow proportion electromagnet, a bypass control end coupled to a bypass electromagnet, and a pneumatic control end coupled to an air pump motor, and further includes a vibrating element electrically coupled to the microcontroller. When the present invention detects a user's shortness of breathing or rapid breathing, the flow control valve, air pump and bypass circuit valve are turned on to supply oxygen with an appropriate oxygen concentration to users to alleviate altitude sickness.

The present invention seeks to identify solutions mitigating a possibility of the delivery tubes becoming blocked. The solutions are especially advantageous for "on-demand" types of emergency oxygen systems, when respiratory gas is supplied in doses, or pulses as demanded by passengers. In some of the innovative systems, a bypass is formed about a delivery valve of each mask. Regardless of the state of the delivery valve, a trickle of respiratory gas flows continuously through each delivery tube to the corresponding mask. This trickle flow typically will be adequate to prevent blockage of the tube notwithstanding moisture accumulation within the mask.

It thus is an optional, non-exclusive object of the present invention to provide systems for delivering respiratory gas as demanded by passengers on-board vehicles.

It is an additional optional, non-exclusive object of the present invention to provide respiratory gas-delivery systems designed to reduce possibility of gas-delivery tubes being blocked downstream of associated pressure (or other) sensors.

It is another object of the present invention to provide gas-delivery systems in which a trickle of respiratory gas flows continuously through each delivery tube to an associated face mask.

More accurately, according to a first aspect of the invention, the system for delivering respiratory gas to passengers on-board an aircraft, comprises:.

Thus, the supply of anti-blocking gas reduces the risk of respiratory detection missed because of an obstruction between the pressure sensor and the face mask in the delivery tube. Indeed, the supply of anti-blocking gas should remove the cause of the obstruction.

Moreover, the anti-blocking device comprises an orifice configured to allow trickle flow of anti-blocking gas.

Thus, the flow of anti-blocking gas is continuous, so that not only the obstruction is promptly removed, but also it is prevented.

The respiratory gas has a high oxygen rate, substantially pure oxygen, the rate of oxygen depending on the type of source of oxygen. The anti-blocking gas can be identical to the respiratory gas and be provided by the source of respiratory gas or a different gas.

Preferably the pressure sensor is configured to sense the pressure away from (upward) the face mask, and the anti-blocking device is configured to supply the face mask with anti-blocking gas through a delivery tube, at least between the pressure sensor and the face mask.

According to a supplementary feature in accordance with the invention, the anti-blocking device preferably comprises a bypass bypassing the delivery valve so as to allow trickle flow of anti-blocking gas regardless of the state of the delivery valve.

Thus, the anti-blocking device can be easily implemented without detrimental effect on the management of the respiratory gas supplying the face mask through the delivery valve.

According to an additional feature in accordance with the invention, the bypass preferably causes trickle flow of anti-blocking gas between the source of respiratory gas and the associated face mask regardless of the state of the delivery valve.

According to an alternative or additional feature in accordance with the invention, the anti-blocking device is preferably configured to supply the face mask with the respiratory gas as anti-blocking gas.

Thus, the system is simpler and the anti-blocking gas provides an additional amount of oxygen to the passenger.

According to another alternative or additional feature in accordance with the invention, preferably the system comprises a main delivery tube connecting the delivery valve to the face mask, the bypass comprises a second delivery tube in parallel with the main delivery tube and terminating at the face mask, the orifice is disposed in the second delivery tube, and the pressure sensor communicates with the second delivery tube downstream the orifice.

According to another alternative or additional feature in accordance with the invention, preferably the system comprises a main delivery tube connecting the delivery valve to the face mask, and the pressure sensor communicates with the main delivery tube downstream the bypass.

In advantageous embodiments, the system preferably further has one or more of the following features:.

According to a second aspect, not according to the invention, the invention relates to a method for delivering respiratory gas to passengers on-board an aircraft, comprising:.

In particular moisture should be understood as liquid moisture, frozen moisture or another element preventing detection of respiration.

In advantageous embodiments, the method preferably further has one or more of the following features:.

The method comprises continuously opening the delivery valve during an opening time, in order to supply the dose of respiratory gas only one time by passenger respiration.

Other objects, features, and advantages of the present invention will be apparent to persons skilled in the art with reference to the remaining text and drawings of this application.

Depicted in <FIG> are components of a four-passenger emergency oxygen system <NUM>. The system <NUM> is placed in the cabin of an aircraft, usually above the head of a group of passengers, preferably a group of <NUM> or <NUM> passengers in the illustrated embodiment. The cabin is pressurized at a cabin pressure, usually referred to as cabin altitude (the altitude corresponding to the cabin pressure) by a pressurizing device which maintains the pressure above a threshold pressure, in other words which maintains the cabin altitude below a corresponding threshold altitude which is usually between two thousand four hundred meters (eight thousand feet) and one thousand eight hundred meters (six thousand feet). The system <NUM> is intended to provide oxygen to the passengers in the event of a loss in cabin pressure.

System <NUM> may include a source of respiratory gas <NUM>. In the embodiment represented in <FIG> the source of respiratory gas <NUM> is a cylinder. The respiratory gas in the source of respiratory gas <NUM> has a high rate of oxygen, higher than <NUM>%, preferably higher than <NUM>%, so that the respiratory gas is quite pure oxygen. The respiratory gas in the source of respiratory gas <NUM> is at a very high pressure, preferably about <NUM> bar (<NUM> psig), but the respiratory gas may be supplied at other gauge pressures instead. Beneficially, the source of respiratory gas <NUM> may be at least one sealed container, with the seal configured to be ruptured to commence flow of respiratory gas from the container.

System <NUM> additionally may include manifold or housing <NUM> in gaseous communication with the source of respiratory gas <NUM>. Housing <NUM> may, if appropriate, have a relief valve <NUM> or other means of venting gas if the pressure thereof exceeds a particular threshold. Downstream of housing <NUM> may be HP reducer and/or a regulator <NUM>, which functions to decrease or otherwise regulate the pressure of the oxygen from housing <NUM> before the oxygen flows to passengers of an aircraft or other vehicle. The HP reducer and/or the regulator <NUM> preferably reduces the absolute pressure between <NUM> bar and <NUM> bar.

As illustrated in <FIG>, the tubing <NUM> may convey lower-pressure oxygen from the regulator <NUM> in parallel to delivery valves <NUM>. Four such delivery valves <NUM> are shown in <FIG>, one delivery valve <NUM> corresponding to each of four passenger masks <NUM>. When a delivery valve <NUM> is open, the respiratory gas may flow through the delivery valve <NUM> to the corresponding mask <NUM> for inhalation by a passenger wearing that mask <NUM>. Preferably, the delivery valves <NUM> reside on one or more control boards <NUM>.

Included as part of the system <NUM> may be an initiator <NUM>. The initiator <NUM> may comprise any suitable mechanism for establishing gas flow from the source of respiratory gas <NUM> to housing <NUM>. One possible version of initiator <NUM> may utilize at least one SMA (Shape Memory Alloy) whose change in shape upon heating may cause a seal of the source of respiratory gas <NUM> to be punctured. The initiator <NUM> is connected to the controller <NUM> by an electrical wire <NUM>, so that the initiator <NUM> is controlled by the controller <NUM>.

The controller <NUM> may be present on the control board <NUM>. The controller <NUM> may receive input from an aircraft altitude sensor <NUM>, a temperature sensor <NUM> and a cabin altitude sensor <NUM>, relating to such values as the altitude of the aircraft and the temperature and pressure of the air ambient in the aircraft cabin. In practice the aircraft altitude sensor <NUM> and the cabin altitude sensor <NUM> detect the pressure outside the aircraft and the pressure in the cabin of the aircraft.

The controller <NUM> additionally may be signaled by respiration sensors <NUM> that detect respiration phases and in particular that corresponding passengers are attempting to inhale through masks <NUM> or are ending exhaling. The respiration sensors <NUM> are away from the face masks <NUM>. The controller <NUM> is preferably connected to the respiration sensors <NUM> by a respiration sensor wire <NUM>. Output signals from the controller <NUM> may be transmitted to initiator <NUM> (signaling that flow of oxygen from source <NUM> is needed) through the electrical wire <NUM> and to the delivery valves <NUM>, through another electrical wire <NUM>, causing them to open and close as appropriate.

Battery <NUM>, or any other suitable electricity source, may power electrical and electronic components of system <NUM>. Although a four-person system <NUM> is detailed for convenience, persons skilled in the art will recognize that system <NUM> may service more or fewer than four passengers as appropriate or desired.

Each face mask <NUM> is configured for use by an aircraft passenger when the cabin altitude is sufficiently high as to induce hypoxia. The face mask <NUM> is directly connected to the delivery valve <NUM> by a delivery tube <NUM> (without reservoir bag), so that the respiratory gas cannot be accumulated. The face mask <NUM> comprises at least one inlet valve <NUM> intended to reduce the risk of ingression of water, ice or dust into the main delivery tube <NUM> while enabling the face mask <NUM> to be supplied with respiratory gas. Each mask <NUM> further comprises an inhalation valve <NUM> which enables each passenger to breath ambient air diluting the respiratory gas. Each face mask <NUM> also comprises an exhalation valve <NUM> to enable gas within the face mask <NUM> to exhaust the face mask <NUM> when the passenger exhales. The inhalation valve <NUM>, the exhalation valve <NUM> and the inlet valve <NUM> are preferably check valves.

<FIG> schematically represents an embodiment of an on-demand emergency oxygen system 10A system providing anti-blocking pulses, not according to the invention. More accurately, <FIG> illustrates the supply of respiratory gas to one of the face masks <NUM>. In order to ease the understanding the system 10A is represented for only one of the face masks <NUM>. The complete system 10A can be directly derived from <FIG> and <FIG>.

In gaseous communication downstream from the source of respiratory gas <NUM> are the regulator <NUM>, the delivery valve <NUM>, the respiration sensor <NUM> and the face mask <NUM>. The regulator <NUM> and the delivery valve <NUM> are connected by the tubing <NUM>. The delivery valve <NUM> and the face mask <NUM> are connected by delivery tube <NUM>. The delivery valve <NUM> is preferably an on/off electro-valve.

<FIG> illustrates a graph of respiratory flow to the face mask <NUM> as a function of time. After the passenger dons the face mask <NUM> and the seal of the source of respiratory gas <NUM> is punctured by the initiator <NUM>, the respiration sensor <NUM> reacts to pressure changes caused by the passenger's breathing. Signals from the respiration sensor <NUM> are transmitted to the controller <NUM>, which opens and closes delivery valve <NUM>. Opening and closing of the delivery valve <NUM> allow doses of respiratory gas to flow from the source <NUM> to the face mask <NUM> via the delivery tube <NUM> to fulfill respiratory requirements of the passenger.

More precisely, when the passenger inhales, the inhalation generates a decrease of the pressure in the face mask <NUM>, the inlet valve <NUM> opens, the pressure in the delivery tube <NUM> decreases and the respiration sensor <NUM> detects the pressure change. The controller <NUM> detects the inhalations of the passenger due to the inhalation signal received from the respiration sensor <NUM> through the respiration sensor wire <NUM> upon detection of the passenger inhalation. The controller <NUM> determines the minimum volume of respiratory gas required by the passenger based on at least one of the cabin altitude, the temperature and the aircraft altitude, sensed by the cabin altitude sensor <NUM>, the temperature sensor <NUM> and the aircraft altitude sensor <NUM>. Then, the controller <NUM> determines a dose D of respiratory gas to be supplied to the face mask <NUM>. The controller <NUM> controls the delivery valve <NUM>. The delivery valve <NUM> is preferably continuously open during an opening time period tD, in order to supply the whole dose D of respiratory gas per respiration for each passenger. In an alternative embodiment, the delivery valve could be controlled in PWM (Pulse Width Modulation) during a predetermined time period or during the inhalation period.

Each dose D has preferably a volume of <NUM> milliliters or more, preferably <NUM> milliliters or more, the volume being considered at the cabin pressure (when supplied in the face mask <NUM>).

Moreover, each face mask <NUM> is supplied with anti-blocking pulses P of anti-blocking gas during a very short time period tP. In the embodiment shown, the anti-blocking gas is respiratory gas supplied by the source <NUM>.

In <FIG>, the flow FP of the anti-blocking pulses P during the opening time period tD of the pulse is shown lower than the flow FD during the opening time period tD of the dose D. The reason is that the time period tP is very short, so that the delivery valve <NUM> is not sufficiently opened to get the flow FD. In a variant the flow FP of the anti-blocking pulses P is equal to the flow FD of the dose D depending on the speed of opening of the delivery valve <NUM> and the time tP.

Both doses D and anti-blocking pulses P may be produced by the same delivery valve (e.g. valve <NUM>); alternatively, different delivery valves may be employed to generate the two pulsed flows.

The volume of anti-blocking gas supplied to the face mask <NUM> is preferably between <NUM> milliliter and <NUM> milliliters, more preferably between <NUM> millimeter and <NUM> milliliter.

Provision of anti-blocking pulses P may be regular as a function of time, in which case they may at times overlap with doses D. Alternatively, anti-blocking pulses P may be synchronized with doses D to avoid this overlap. As another approach, an anti-blocking pulse P may be generated in response to failure of the respiration sensor <NUM> to detect a respiration after a specified interval of time.

In particular, in an embodiment, the pulse of anti-blocking gas is supplied to the face mask <NUM> at a predetermined time period TD after the dose D for each respiration (unless another respiration is detected in the meantime), the time period TD being preferably between <NUM> seconds and <NUM> seconds.

Moreover, the face mask <NUM> may be repeatedly supplied with anti-blocking pulses P at regular interval TP of time which is preferably between <NUM> seconds and <NUM> seconds.

In a preferred alternative embodiment, the time period TD is adapted to the breathing pattern of the user. Data relating to the breathing pattern of the associated passenger are acquired over a period of usage of several breathing cycles (for instance the last <NUM> breathing cycles). The acquired data preferably include the time period of the breathing cycle and may also include the time period of the inhaling phase and the time period of the exhaling phase. The systems 10A, 10B, 10C may include further pressure sensors if appropriate. Then, statistical information including an average time period and a standard deviation of the associated passenger are calculated by the controller <NUM>. The controller <NUM> also calculates a threshold time based on the statistical information. Preferably, the threshold time is calculated the average time (µ) plus two standard deviations. If the delay between two respirations exceeds the threshold time, say, the average time plus two standard deviations, then a deblocking pulse is delivered. This would reduce the oxygen wasted by delivering a deblocking pulse for a slow breather (e.g. a healthy adult) and could predict and deblock the mask of a fast breather (e.g. a child) earlier.

Otherwise, it should be noticed that the time period tD of the dose D is adjusted based on the cabin pressure, the temperature and/or the aircraft pressure whereas the cabin pressure, the temperature and the aircraft pressure have no influence on the time period tD of each pulse P.

In general, the respiratory gas is most efficiently supplied to passengers during the early portions of their inhalation cycles; ambient air (or a mixture of ambient air and oxygen) typically may be furnished for the remainder of the inhalation cycles.

In order to reduce the risk of detection failure of a passenger respiration by the respiration sensor <NUM>, in case of depressurization occurrence detected by the cabin altitude sensor <NUM> or by the opening of the box housing the passenger masks or other means, the controller <NUM> controls the delivery valve <NUM> associated with each passenger in order to simultaneously supply each face mask <NUM> with a pulse P as a cautionary measure, before detecting any respiration and providing a dose D of respiratory gas.

<FIG> schematically illustrates an alternative system 10B of the present invention. Like system 10A, system 10B may include a supply of respiratory gas (e.g. oxygen cylinder <NUM>) in gaseous communication with regulator <NUM>, delivery valve <NUM>, respiration sensor <NUM>, face mask <NUM>, and delivery tube <NUM>. However, additionally included in system 10B may be bypass <NUM>. As shown in <FIG>, bypass <NUM> beneficially originates upstream of valve <NUM> (preferably between regulator <NUM> and valve <NUM>) and terminates downstream of the delivery valve <NUM> (preferably between valve <NUM> and face mask <NUM>). Bypass <NUM> hence may allow respiratory gas to flow from cylinder <NUM> to face mask <NUM> at all times system 10B is active, regardless of whether valve <NUM> is open or closed.

The continuous flow of pressurized gas allowed by bypass <NUM> may operate to prevent ingress of water or ice into tube <NUM>. Even should such water or ice block the delivery tube <NUM>, moreover, the pressurized flow may act to discharge the blockage from the delivery tube <NUM> (back into mask <NUM>). Generally, however, the majority of respiratory gas will continue to be supplied to the passenger through the opening and closing of valve <NUM>, with only a trickle of gas flowing through bypass <NUM>. In the embodiment shown in <FIG>, bypass <NUM> preferably comprises an orifice <NUM> of restricted section.

Bypass <NUM> may be created in any suitable manner. As one example, the orifice <NUM> may constitute a tube of specified diameter smaller than the diameter of the delivery tube <NUM>. As another example, the orifice <NUM> may include a bleed opening of delivery valve <NUM> upstream of its closure element and which communicates with delivery tube <NUM>. As another example, the delivery valve <NUM> may include a moving element and a seat, the moving element being mobile between a first position in which the moving element contact the seat and a second position in which the moving element is away from the seat, and a bleed opening remaining between the moving element and the seat due to a slot in the seat, the slot forming the orifice <NUM>.

Depicted in <FIG> is an exemplary graph of respiratory gas flow to a face mask <NUM> as a function of time. The graph illustrates the concept of systems 10B, as well as alternative systems 10C and 10D: Opening and closing of the delivery valve <NUM> produces doses D of oxygen available for respiration by the passenger having donned the face mask <NUM>. Meanwhile, the bypass <NUM> provides a continuous flow CF of anti-blocking oxygen, preferably at a (trickle) rate whose amplitude FT is significantly lower than the amplitude FD of doses D, preferably at least <NUM> times lower than the amplitude FD of doses D. The amplitude FT of the anti-blocking gas is preferably <NUM> milliliter per minute or less.

Exemplary system 10C of the present invention is schematically represented by <FIG>. System 10C may be similar to system 10B except that the bypass <NUM> is shown as terminating at the face mask <NUM>, effectively forming a second delivery tube <NUM> in parallel with the main delivery tube <NUM>. <FIG> additionally illustrates respiration sensor <NUM> as communicating with the second delivery tube <NUM> if desired.

Exemplary system 10D of the present invention is schematically represented by <FIG>. System 10D may be similar to system 10C except that the bypass <NUM> is shown as separate from the flow of respiratory gas from the source <NUM>. Instead, the bypass <NUM> is supplied by a source of anti-blocking gas <NUM> and terminating at the face mask <NUM>, effectively forming a second delivery tube <NUM> in parallel with the main delivery tube <NUM> and separate from the main delivery tube <NUM>.

Consequently, the source of anti-blocking gas <NUM> may contain a gas different from the respiratory gas, for instance air or a gas much lighter than oxygen. In a variant, the source of anti-blocking gas <NUM> is a blower or similar, blowing ambient air into the second delivery tube <NUM>.

The respiration sensor <NUM> communicates with the second delivery tube <NUM>.

These examples are not intended to be mutually exclusive, exhaustive, or restrictive in any way, and the invention is not limited to these example embodiments but rather encompasses all possible modifications and variations within the scope of any claims ultimately drafted and issued in connection with the invention.

Claim 1:
A system (<NUM>, 10A, 10B, 10C, 10D) for delivering respiratory gas to passengers on-board an aircraft, comprising:
(i) a source of respiratory gas (<NUM>),
(ii) at least a face mask (<NUM>) for passenger,
(iii) a delivery valve (<NUM>) interposed between the source of respiratory gas (<NUM>) and the face mask (<NUM>) associated to the delivery valve (<NUM>), and
(iv) a pressure sensor (<NUM>) configured to detect passenger respiration and send a respiration signal upon detection of the passenger respiration,
(v) a controller (<NUM>) configured to control the delivery valve (<NUM>) opening for supplying the face mask (<NUM>) with a dose (D) of respiratory gas based on the passenger respiration detection, and
(vi) an anti-blocking device (<NUM>, <NUM>, <NUM>, P, CF) configured to supply the face mask (<NUM>) with anti-blocking gas (<NUM>, <NUM>), so that blockage is removed,
characterized in that
the anti-blocking device comprising an orifice (<NUM>) configured to allow trickle flow (CF) of anti-blocking gas (<NUM>, <NUM>).