EP0546909B1 - Emergency respiratory equipment for aircraft passengers - Google Patents

Description

The invention relates to installations for protecting aircraft passengers against the risk of cabin depressurization during flights at high altitude.

Conventional passenger protection installations include a supply of oxygen connected to a distribution center which, in the event of cabin depressurization at high altitude, supplies, at a pressure which increases with altitude, a pipeline to which passenger masks are connected by a flexible tube fitted with a flow limitation throttle. Such an installation is described in document GB-A-828,362.

The protective installation is of infrequent use. It must be made of light, simple components, of economical construction, unlikely to break down. At present, the masks used in such installations generally consist of a simple shell of semi-flexible material, supplied continuously through an economizer bag into which the flexible tube opens. The economizer bag is connected to the inside of the face cover by an intake check valve. An exhalation valve, calibrated to maintain a slight overpressure in the face cover relative to the ambient atmosphere, is fixed on the latter. The economizer bag collects the oxygen flow provided by the source during the expiration periods, while the intake valve is closed, instead of letting it escape the atmosphere.

The supply pressure supplied by the central unit is chosen, depending on the section of the throttles, so as to provide the masks with an average oxygen flow rate sufficient for maintain, at each altitude, the minimum tracheal partial pressure required by regulations.

This solution gives acceptable results up to an altitude of approximately 12,200 meters. Beyond that, current solutions do not provide effective protection against hypoxia. However, more and more airliners and business aircraft, once lightened with part of their fuel, exceed 12,200 meters.

At first glance, it appears that satisfactory protection requires replacing conventional installations of the type defined above with installations comprising, for each mask, a demand regulator and a balanced exhalation valve (i.e. say insensitive to variations in downstream pressure), allowing passengers to breathe pure oxygen under pressure by avoiding the opening of the exhalation valve as soon as a determined overpressure in relation to the atmosphere is reached. In practice, the cost and complexity of such a solution would be prohibitive.

The present invention aims to provide an installation providing acceptable protection up to altitudes of approximately 13,700 meters, at the cost of modifications to existing installations which remain limited.

The invention starts from the observation that, in reality, current installations do not allow the wearer of the mask to breathe pure oxygen. During the inspiratory peaks, the oxygen flow and the volume of oxygen coming from the saving bag are insufficient to avoid the appearance, in the mask, of a slight depression which is enough to cause the entry of dilution air by the anti-suffocation valve with which the mask is provided and by the leaks between the face cover and the skin. The average flow rate supplied through the throttle is not sufficient for the needs of some of the passengers and / or is insufficient to ensure the pulmonary ventilation during periods of agitation. However, it is not possible to oversize the diaphragm or to increase the supply pressure systematically, as this would lead to a waste of oxygen and would oblige to significantly increase the volume and the weight of the oxygen reserve. .

To solve the problem, the invention proposes an installation characterized in that the power station is designed to, in the event of depressurization, temporarily or beyond a given cabin altitude (of around 12,200 meters), provide the channeling of oxygen under a determined pressure p1, of the order of twice the pressure p2 supplied immediately below the determined altitude, and in that each mask has a shaped face cover, comprising a seal flexible sealing lip and an unbalanced exhalation valve.

When the reserve and the power station constitute an oxygen generator by chemical reaction, this generator can be simply provided to supply an oxygen flow at least twice the flow supplied subsequently, for a period of time sufficient to allow the crew to bring the aircraft to an altitude below 12,200 meters, for example for approximately 3 minutes: this case is often that of an installation intended for a business aircraft.

With this arrangement, the additional capacity required from the reserve is limited to what is necessary to protect passengers against hypoxia for the time required for the crew to bring the aircraft back to a safe altitude.

In the case of airliners, mask boxes are interposed between the distribution center and the pipeline. Each box contains respiratory masks and is provided with a lock allowing to release the masks who fall in front of the passengers in the event of depressurization. In accordance with an advantageous embodiment of the invention, the central unit can be provided for supplying the mask boxes under a high pressure p1 which is higher than the pressure p2 to be supplied upstream of throttles each supplying a mask for the lower altitudes at 12,200 meters and each mask box is then fitted with an altimeter regulator located upstream of the throttles and means making it possible to short-circuit the regulator in response to the reception of oxygen at high pressure p1 coming from the central distribution.

The oxygen supply at pressure p ₁ does not significantly increase the overpressure in the mask, limited by the exhalation valve. But it causes a sharp increase in flow, avoiding dilution by the entry of outside air and guaranteeing the inhalation of practically pure oxygen.

Such a box fulfills some of the functions which are normally provided by the distribution center in current conventional installations.

• la figure 1 est un schéma de principe d'une installation suivant l'invention, une seule des boîtes à masques et un seul des masques étant représentés complètement ;
• la figure 2 est un schéma d'un détendeur altimétrique utilisable dans une boîte du genre montré en figure 1 ;
• la figure 3 est un schéma de principe, en coupe passant par l'axe des clapets, d'un organe de liaison entre le couvre-face et le sac économiseur d'un masque utilisable dans l'installation de la figure 1 ;
• la figure 4 montre une courbe représentative d'une loi de variation de la pression en fonction de l'altitude utilisable pour mettre en oeuvre l'invention,
• la figure 5 montre, à titre d'exemple, la loi de variation de la pression de sortie de la centrale de distribution en fonction du temps, pour un profil de descente hypothétique particulier ;
• la figure 6 montre schématiquement une loi de variation du débit adoptable pour un générateur chimique.

The invention will be better understood on reading the following description of particular embodiments, given by way of nonlimiting examples. The description refers to the accompanying drawings, in which:

• Figure 1 is a block diagram of an installation according to the invention, only one of the mask boxes and only one of the masks being shown completely;
• Figure 2 is a diagram of an altimeter regulator usable in a box of the kind shown in Figure 1;
• Figure 3 is a block diagram, in section passing through the axis of the valves, of a connecting member between the face cover and the economizer bag of a mask usable in the installation of Figure 1;
• FIG. 4 shows a curve representative of a law of variation of the pressure as a function of the altitude which can be used to implement the invention,
• FIG. 5 shows, by way of example, the law of variation of the outlet pressure of the distribution center as a function of time, for a particular hypothetical descent profile;
• FIG. 6 schematically shows a law of variation of the adoptable flow rate for a chemical generator.

The installation shown diagrammatically in FIG. 1 can in particular be used on a passenger airliner. This installation comprises a reserve of pressurized oxygen 10 provided with a regulator 12 supplying oxygen under a pressure of 5 to 6 bars to a distribution center 14. The power station in turn feeds a general pipe 16 on which are connected mask boxes 18 of which only one is shown in detail. The boxes are distributed above the rows of seats and each is designed to release the masks 21 which it contains in the event of depressurization. For this, the bottom of the box 18 can constitute a cover provided with a latch 20 which is disarmed in response to the appearance, in the distribution pipe 16, of a pressure greater than a determined value p0. Unlocking can be done in another way or the masks can be permanently available to passengers, for example on business aircraft.

Each box 18 has a pipe 22 to which the masks are each connected by means of a throttling restrictor 24. In the case illustrated in Figure 1, a valve 26 is interposed between the pipe and each mask 21, in series with the throttle 24. This valve is designed to be opened by pulling the passenger on a strap 28 which doubles the flexible pipe 30 for connection with the mask 21.

The mask itself comprises a face cover 32 provided with an elastic harness 34 for fixing on the head and with a flexible economiser bag 36.

The general arrangement described so far is classic. However, in accordance with the invention, the distribution center 14, each mask box 18 and each mask 21 have a particular constitution.

The distribution center 14 is designed to supply the general pipe 16 with oxygen at a pressure which varies as a function of the pressure in the cabin or "cabin altitude" according to two different laws, depending on whether this altitude is less than or greater than 12,200 meters , or 40,000 feet. As indicated above, the power station 14 supplies, when the altitude exceeds, even slightly, 12,200 meters, the oxygen under a pressure p1 which is practically twice the pressure p2 supplied at a slightly lower altitude. at 12,200 meters.

The power station 14 shown in FIG. 1 is constructed so as not only to achieve this result, but also to provide, immediately after the detection of a depressurization beyond 3,800 meters "cabin altitude" (12,500 feet), a brief pressure peak intended to open the locks 20 of the boxes 18. Many other constitutions of the control unit 14 would be possible, pneumatically or electronically controlled from signals supplied by pressure sensors.

The central unit 14 represented comprises a housing having an inlet connected to the reserve of oxygen under pressure 10 and an outlet for connection with the general distribution pipe 16. It can be regarded as having two stages 38 and 40 of similar constitution.

The first stage 38 comprises a valve 42 fixed to two membranes 44 and 46 and cooperating with a seat which surrounds the oxygen intake coming from the reserve 10. The valve 42 thus controls the communication between the reserve and a regulator 48 of conventional constitution , connected by a passage 50 to the outlet 52. This regulator 48 maintains a constant relative pressure at the outlet 52 with respect to the ambient pressure, admitted by an orifice 54, as long as the second stage 40 does not intervene. The two membranes 44 and 46 have a different surface. They define a chamber 58 connected to the atmosphere and they are subjected to the action of a spring 56 which tends to apply the valve 42 to its seat.

The membrane 46 of larger section is subjected to the difference in pressures between the chamber 58 and a chamber connected to the inlet by a throttled passage 60. The valve 42 and the membranes are dimensioned so that the valve opens as soon as the chamber 56 is emptied, that is to say when the cabin altitude reaches 3800 meters.

The second stage 40 has a constitution similar to the first. The chamber delimited by the housing and the large area membrane 46a is connected to the valve of the valve 42a by a constriction 60a. The surfaces of the membranes 44a and 46a are provided so that the valve of the second stage opens as soon as the chamber 56a is emptied, that is to say when the cabin altitude reaches 12,200 meters.

The central unit 14 shown is designed to supply, at its outlet 52, oxygen at the inlet pressure for a short period of time (sufficient to open the locks of the boxes 18) when the pressure in the cabin corresponds to an altitude greater than 12,500 feet.

• Aussi longtemps que l'altitude cabine est inférieure à 12 500 pieds (3 800 mètres environ) le clapet 42 reste fermé par la pression dans la chambre 56. Cette chambre est en effet alimentée à la pression de sortie du détendeur 12 car le clapet 62 reste fermé.
• En cas de dépressurisation au-dessus de 12 500 pieds, la capsule 64 ouvre le clapet 62. La chambre 56 se vide. Le clapet 42 s'ouvre. L'oxygène provenant de la source 12 alimente le second étage par un passage 66. Sous l'effet de la pression exercée sur le clapet 42a percé du passage étranglé 60a, ce clapet 42a s'ouvre et la pression fournie par le détenteur 12 est transmise directement à la sortie 52.
• Tant que l'altitude cabine est inférieure à 40 000 pieds (12 200 mètres environ) la capsule 64a n'ouvre pas le clapet 62a du second étage : la chambre 56a se remplit en quelques secondes d'oxygène provenant du premier étage par l'étranglement 60a. Le sens des forces de pression s'inverse et le clapet 42a se referme.
• Lorsque l'altitude cabine dépasse 40 000 pieds, la capsule 64a ouvre le clapet 62a. La chambre 56a se vidange et le clapet 42a s'ouvre. La pression fournie par le détendeur 12 est transmise directement à la sortie 52.

The operation is as follows:

• As long as the cabin altitude is less than 12,500 feet (approximately 3,800 meters) the valve 42 remains closed by the pressure in the chamber 56. This chamber is in fact supplied at the outlet pressure of the regulator 12 because the valve 62 remains closed.
• In the event of depressurization above 12,500 feet, the capsule 64 opens the valve 62. The chamber 56 empties. The valve 42 opens. The oxygen coming from the source 12 feeds the second stage through a passage 66. Under the effect of the pressure exerted on the valve 42a pierced with the throttled passage 60a, this valve 42a opens and the pressure supplied by the holder 12 is transmitted directly to output 52.
• As long as the cabin altitude is less than 40,000 feet (approximately 12,200 meters) the capsule 64a does not open the valve 62a on the second stage: the chamber 56a is filled in a few seconds with oxygen coming from the first stage through the choke 60a. The direction of the pressure forces is reversed and the valve 42a closes.
• When the cabin altitude exceeds 40,000 feet, the capsule 64a opens the valve 62a. The chamber 56a is emptied and the valve 42a opens. The pressure supplied by the regulator 12 is transmitted directly to the outlet 52.

FIG. 5 shows a sequence corresponding to a slow decompression during which the cabin altitude exceeds 12,200 meters followed by a return to the ground. At time t0, the outlet pressure p1 of the regulator is applied to the boxes 12 to open the latches 20, provided to be triggered from a pressure p0 less than p1. The pressure then drops to a value p2, then rises to p1 when the altitude of 40,000 feet is reached. When the device descends below 40,000 feet, the pressure drops to the p2 value which remains up to an altitude which is generally less than 12,500 feet and which is for example 10,000 feet (approximately 3,100 meters).

In each of the boxes 18, the line 22 is supplied by a regulator 70 when the pressure applied is equal to p2, by a bypass valve 72 when the pressure applied is equal to p1. The by-pass or short-circuit valve 72 may be constituted by a simple membrane pushed back to a position for closing a seat by the pressure which prevails in the cabin and by the force of a spring and, in the opposite direction , by the pressure force prevailing in the pipe 22, at its center, and the inlet pressure in the box 18, at its periphery. The diaphragm and the spring are dimensioned so that the short-circuit valve 72 opens when the pressure exceeds a determined value between p2 and p1.

The regulator 70 has for example the constitution shown in FIG. 2, having a membrane 74 provided with a pusher for opening a ball valve 76 and a capsule 78 provided for bearing, directly or by means of a spring, on the membrane when the altitude in the cabin exceeds 10,000 feet. The pressure in the pipe 22 then has a law of variation as a function of the cabin altitude of the kind shown in FIG. 4.

As indicated above, obtaining satisfactory protection involves avoiding the entry of air into the mask from the atmosphere.

To achieve this result, the face cover 32 of the mask 21 (FIG. 3) has an internal lip 80 of flexible elastomer, delimiting an opening of triangular shape and shaped so as to be applied against the bridge of the nose and the face by internal pressure. The mask shown in FIG. 3 comprises a valve block 82 which incorporates a flexible valve 84 for admission from the economizer bag 36 according to the arrows f0. If the bag is empty, the assembly constituted by the flexible valve 84 and the box which supports it can be lifted to allow passage to additional air, the path of which is then the one indicated by the arrows f1.

The oxygen supply to the economizer bag 36 can be carried out by a flexible pipe 30 shown in front of the face cover in FIG. 3 but which in practice will rather be placed on the side, as shown diagrammatically in FIG. 1.

The exhalation can be carried out for example through an additional valve 86 calibrated by a spring, shown diagrammatically in FIG. 1, or through an annular exhalation valve (not shown) at the periphery of the block 82 having a flexible obturator of which the stiffness fixes the maximum overpressure in the mask.

If each mask is individually supplied by a chemical generator, this is provided to supply, from the moment it is started, an oxygen flow rate which varies according to a law of the kind shown in FIG. 6, making it possible to supply the oxygen required during the descent in the most critical conditions, from an altitude which generally cannot exceed 45,000 feet, that is to say 13,700 meters. In this case, the law of variation given by the adoption of a variable composition or a variable section of the "candle" of oxygen supply can be of the kind given in figure 6. It is provided to give a flow approximately 6 liters per minute (under normal temperature and pressure conditions) for a time sufficient to bring the aircraft back from the maximum altitude of 13,700 meters to 12,200 meters for example, then gradually reduce the flow while maintaining it for a sufficient time to stabilize the aircraft at an intermediate altitude, for example 18,000 feet (5,500 meters) before bringing it back to the safety altitude of 10,000 feet (3,050 meters). In practice, a maximum delivery time of approximately 3 minutes will generally be satisfactory.

Claims (5)

1. Apparatus for protection of aircraft passengers against depressurisation dangers, comprising an oxygen storage (10) connected to a distribution unit (14) which, upon loss of pressurisation at high altitude, feeds, under a pressure which increases responsive to altitude, a pipe to which the masks (32) of the passengers are connected via a flexible hose (30) having a flow limitation throttling orifice (24),
      characterized in that the unit is arranged for, temporarily or beyond a determined cabine altitude, deliver oxygen to the pipe under a determined pressure, about twice the pressure delivered immediately under said determined altitude and in that each mask comprises a shaped face cover (32), having a flexible joint with flexible sealing lips.
2. Apparatus according to claim 1, characterized in that the storage (10) and the unit (14) constitute a generator of oxygen resulting from a chemical reaction, said generator being arranged for delivering a flow rate of oxygen which is at least twice that which is later delivered, for about 3 minutes.
3. Apparatus according to claim 1, characterized in that it comprises mask presentation boxes (18) located between the distribution unit (14) and the pipe, in that the unit (14) is arranged for feeding the mask boxes (18) under the predetermined pression which is higher than the pressure to be delivered upstream of the throttling orifices for those altitudes which are lower than said determined attitude, and in that each mask box is provided with a barometric pressure reducing valve (70) and with means (72) for by-passing the barometric pressure reducing valve (70) responsive to delivery of the determined pressure delivered by the distribution unit.
4. Apparatus according to claim 1, 2 or 3, characterized in that the determined altitude is of about 12,200 meters.
5. Apparatus according to any one of the preceding claims, characterized in that each mask is connected to the pipe via an inspiration valve is provided with an economized bag and comprises a non-compensated exhalation valve.

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