EP1579890A1 - Regulation method and device for a respirator - Google Patents

Abstract

The method involves measuring the ambient pressure and the instantaneous inhaled breathe-inflow rate in terms of ambient volume in real time. The minimum oxygen content in the complete inhalation phase is computed based on the pressure in order to comply with the respiratory standards. The instantaneous flow rate of additional oxygen is controlled so as to satisfy the standard requirements within a safety margin. An independent claim is also included for a demand and dilution mask regulator.

Description

The present invention generally relates to regulators at the demand and dilution by ambient air intended to provide respiratory gas to meet the needs of a wearer wearing a mask, using a supply by a source of pure oxygen (oxygen cylinder, generator chemical or liquid oxygen converter) or of a highly enriched gas oxygen, such as an onboard generator said obogs, as well as the devices individual respiratory systems comprising such regulators.

It is particularly concerned with methods and devices for regulating intended for breathing apparatus intended for civil aircraft crews or military personnel who, beyond a specified cabin altitude, must receive respiratory gas representing at least a minimum flow of oxygen which is depending on the altitude, or, at each inhalation, a quantity of oxygen corresponding to a minimum oxygen content of the inhaled mixture. The law of minimum flow of oxygen is set by standards, which are currently the object, for the civil domain, of a FAR regulation.

Current regulators on demand can be worn by the mask ; this is the most common case in the civil case of fighter jets, where the regulator is often on the seat of the carrier. These regulators have an oxygen supply circuit connecting an input of oxygen under pressure at an admission in the mask and having a main valve, generally controlled pneumatically by a pilot valve, and a dilution air supply circuit from the ambient atmosphere. The opening and closing of the oxygen supply occurs in response to the inspiration and expiration of the wearer of the mask, at cabin altitude and possibly at the position of selection means, operable manually, allowing normal operation with dilution, a operation with feed without dilution, and operation with overpressure. Regulators of this type are described in particular in the document FR-A-2 778 575, to which reference may be made.

These known regulators are robust, have a safe operation and can be achieved relatively simply even for flow rates of important inspiration. They have the disadvantage that, to respect the minimum oxygen flow rate (from pure oxygen supply and air from dilution) in all operating situations it is necessary to in such a way that in most of the field of operation, they call a pure oxygen flow much higher than the one that would be necessary. This requires carrying a volume of oxygen higher than the actual physiological needs or the presence of a generator on board having better performance than would be indispensable.

In addition, an electronically controlled regulator has been proposed. of the respirator mask for a fighter jet pilot (patents FR 79 11 072 and US-A-4 336 590. This regulator uses sensors of pressure and an electronic control of a solenoid valve oxygen flow rate. The dilution air is sucked in by a venturi. This electronically controlled regulator has the advantage of allowing a better adaptation of the flow of pure oxygen supplied to the physiological requirements. But he presents a number of limitations. In particular the dilution depends on operation of an ejector. The nature of the oxygen flow control pure and dilution airflow makes that the oxygen brought in by the dilution air, whose flow rate is a function of oxygen flow and other state parameters (including the inspiratory request of the wearer) can hardly be taken into counts in pure oxygen flow control. In most cases, the command will cause a pure oxygen flow leading to an excess oxygen delivered to the carrier and it is not intended to use the command electronic system so as to obtain an operation which makes it possible to provide a flow of oxygen which is in all conditions as close as possible to the minimum provided by the regulations.

The present invention aims in particular to provide a method and a better than those previously known to practice requirements; it aims in particular to provide a regulator to bring the required flow of oxygen closer to the source of the is actually necessary.

For this reason, it is notably proposed a different approach from those previously adopted; it involves estimating or measuring, in time the essential parameters determining oxygen requirements (altitude cabin, instantaneous inspiratory volume flow reduced to the conditions of the cabin, percentage of oxygen in the inhaled mixture as imposed by regulations where they exist and by physiology, ...) and to deduce the instantaneous flow rate of additional pure oxygen to be supplied at every moment.

• on mesure en temps réel le débit inspiratoire volumique instantané inhalé ramené aux conditions ambiantes (directement ou à partir de la mesure du débit d'air de dilution inhalé dans le masque, en tenant compte de l'oxygène additionnel), et la pression ambiante,
• à partir de la pression ambiante on détermine la teneur minimale en oxygène à réaliser sur l'ensemble de l'inhalation pour respecter la norme respiratoire, et
• on estime et on commande le débit instantané d'oxygène pur additionnel de façon à remplir les exigences de la norme avec une marge de sécurité qui sera généralement de quelques pour cent.

According to one aspect of the invention, it is therefore proposed a method of regulating the additional oxygen flow brought from an inlet of oxygen under pressure, from a source, to an admission in a respiratory mask provided with a ambient air dilution inlet, according to which:

• the inhaled instantaneous volume inspiratory flow rate is measured in real time and is brought back to the ambient conditions (directly or from the measurement of the inhaled dilution air flow rate in the mask, taking into account the additional oxygen), and the ambient pressure,
• from the ambient pressure is determined the minimum oxygen content to be achieved throughout the inhalation to meet the respiratory norm, and
• the instantaneous flow rate of additional pure oxygen is estimated and controlled to meet the requirements of the standard with a margin of safety that will generally be a few percent.

It can be provided a regulation of the dilution air by setting the section of passage using an altimetric capsule, without intervention of a venturi; it can also be carried out by piloted flap, again without ejector, combining the favorable features of the regulators purely pneumatic to those of a known regulator electronic.

In a first embodiment, the oxygen flow rate estimation additional is continued throughout the inhalation period. This translates in fact by adjusting the entire volume of additional oxygen provided during the entire complete inhalation. In another mode of realization, which in principle saves even more oxygen, account is taken of the fact that the respiratory tract has a volume which does not participate in gas exchange. More precisely, the fraction of inhalation mixture that is inhaled last does not reach the alveoli lung. It simply enters the upper airways from where it is rejected to the atmosphere at the expiration. The following process the other embodiment uses this finding, for example by detecting the instant from which the inhaled instantaneous flow falls below a predetermined threshold as indicating the beginning of the final phase of inhalation, during which oxygen is not used, and then cutting off the finish additional oxygen

• il est effectué, à la fin de chaque cycle respiratoire, une estimation de la quantité totale d'oxygène qui sera requise au cours de l'inhalation suivante ( par exemple par calcul d'une moyenne sur plusieurs cycles précédents) et
• on envoie la totalité de l'oxygène additionnel requis pendant une phase initiale de l'inhalation.

In yet another embodiment, which makes it possible to use the above finding that it is the additional oxygen sent during an initial phase of the inspiratory cycle which is the best used,

• at the end of each respiratory cycle, an estimate is made of the total amount of oxygen required during the next inhalation (for example, by averaging over several previous cycles) and
• all the additional oxygen required is sent during an initial phase of inhalation.

A comparison is made during the next phase of the cycle inspiratory between the standard cycle thus evaluated and the course of the cycle real; in case of discrepancy leading to an oxygen requirement higher than that provided, an additional amount of oxygen determined as a function of the gap is provided.

In all cases, there is, from the determination of the quantity of oxygen necessary for the physiological needs, calculation of the quantity of pure oxygen to forcefully add to the oxygen in the air at a 21% content (or higher in case of conditioned atmosphere) inhaled directly from the ambient atmosphere and whose flow is generally not not ordered.

• un circuit d'amenée d'oxygène reliant une entrée d'oxygène sous pression, provenant d'une source, à une admission dans un masque respiratoire par l'intermédiaire d'une première vanne de commande directe de débit,
• un circuit de dilution amenant directement au masque de l'air provenant de l'atmosphère, pouvant être muni d'une soupape à ouverture commandée par la pression ambiante,
• un circuit d'expiration comportant une soupape anti-retour d'expiration reliant le masque à l'atmosphère, et
• un circuit électronique de commande d'ouverture de la vanne de commande directe de débit, en fonction de signaux fournis par au moins un capteur de la pression atmosphérique ambiante et un capteur du débit d'air inhalé ou du débit total inhalé.

The invention also proposes a regulating device comprising:

• an oxygen supply circuit connecting a pressurized oxygen inlet from a source to an admission in a breathing mask via a first direct flow control valve,
• a dilution circuit bringing directly to the mask air from the atmosphere, which can be provided with an opening valve controlled by the ambient pressure,
• an exhalation circuit including a non-return expiration valve connecting the mask to the atmosphere, and
• an electronic control circuit for opening the direct flow control valve, based on signals provided by at least one ambient atmospheric pressure sensor and an inhaled airflow or inhaled total flow rate sensor.

The air flow sensor can have various constitutions. for example it is of the type of depressor, commercially available. Such a sensor determines the pressure drop at the passage of a constriction and provides a signal representative of the flow. It can also be of the hot wire type.

Such a constitution is "hybrid" in that it associates pneumatically controlled regulator features in terms of air flow to an electronic control of the additional pure oxygen flow, allowing a flexible regulation.

The term "oxygen under pressure" or "pure oxygen" must be interpreted as covering as well the case of pure oxygen, provided for example by a bottle, that of air very enriched in oxygen, typically beyond 90%. In the latter case the effective oxygen content of the enriched air an additional parameter to be taken into account and it must be measured.

The flow control valve may be progressive opening, or "all or nothing" type; it is commanded in the latter case by a signal Pulse width modulated electric, with opening duty cycle (duty ratio) adjustable and a pulse rate higher than 10Hz.

The control law stored in the electronic circuit is such that the regulator provides, in "normal" operation, a flow of oxygen total at least equal to that provided by the regulations for each altitude cabin, from the source and the dilution air.

In general, regulators are intended to allow not only normal operation with dilution, but also operation with pure oxygen supply expanded (so-called "100%" operation), or pure oxygen with a given overpressure compared to the ambient atmosphere (so-called "emergency" operation). These last modes in particular are necessary when the risk of presence of smoke or toxic gas in the environment is taken into account. The electronic circuit may be provided to cause the closing of the valve dilution in response to manual or automatic control. A additional solenoid valve with manual and / or automatic be planned to maintain an overpressure in the mask by establishing on the valve exhalation overpressure tending to close it.

Closure of the dilution valve is advantageously controlled by means of a two-position solenoid valve which, in a state, causes the valve to close by feeding the valve seat against a shutter carried by an element sensitive to the pressure of the atmosphere ambient and, in the other position, bring a valve seat into a determined position, allowing adjustment of the dilution air flow rate by displacement or deformation of the element.

• le circuit d'amenée d'oxygène pur peut être en totalité placé dans un boítier fixé à un masque, ou
• une partie de ce circuit, et notamment la première électrovanne, peut être intégré à une boíte de stockage du masque en position d'attente.

The invention is capable of many embodiments. In particular, the various components of the regulator can be distributed in different ways between a housing carried by the mask and a box for storing the mask outside periods of use or any other external housing, including online, so that it remains directly accessible by the wearer of the mask. For example :

• the pure oxygen supply circuit can be entirely placed in a housing fixed to a mask, or
• a part of this circuit, and in particular the first solenoid valve, can be integrated in a box for storing the mask in the waiting position.

• la figure 1 est un schéma pneumatique et électrique montrant les constituants concernés par l'invention d'un régulateur qu'on peut qualifier de « à actionneur intégré » ;
• la figure 2, similaire à la figure 1, montre une variante de réalisation ;
• la figure 3 est un diagramme montrant une courbe type de variation du débit d'oxygène requis par les règlements en fonction de l'attitude cabine ;
• la figure 4 montre un faisceau de courbes de variation des débits d'oxygène de l'appel inspiratoire à différentes altitudes cabine.

The above characteristics, as well as others, advantageously usable in connection with the preceding ones, but which can be independently, will appear better on reading the following description of particular embodiments given as non-specific examples. limiting. The description refers to the accompanying drawings, in which:

• Figure 1 is a pneumatic and electrical diagram showing the constituents concerned by the invention of a regulator that can be described as "integrated actuator";
• Figure 2, similar to Figure 1, shows an alternative embodiment;
• FIG. 3 is a diagram showing a typical curve of oxygen flow variation required by the regulations as a function of cab attitude;
• Figure 4 shows a beam of oxygen flow variation curves of the inspiratory call at different cabin altitudes.

The regulator shown in Figure 1 consists of two parts, one 10 incorporated in a housing carried by a mask not shown and the other 12 carried by a mask storage box. This box can have a classical general constitution, comprising a chassis delimiting a volume of reception, closed by doors and which makes the mask stand out. The opening doors by extraction of the mask causes the opening of a tap supply of oxygen.

The part carried by the mask is constituted by a housing in several assembled rooms, in which dwellings and passages to define several traffic paths.

A first circulation path connects an oxygen inlet 14 under pressure at an output 16 to the mask. A second path connects an entry 20 dilution air at an outlet 22 to the mask. The flow of oxygen in the first path is regulated by an electrically operated tap. In the case shown, this valve is a proportional valve 24, controlled in voltage, which connects the input 14 and the output 16, powered by a conductor 26, it connects the entrance and the exit. It is also possible to use a valve of the type "all or nothing", controlled in pulse width, with a RCO (report cyclical opening or duty cycle) variable.

On the path of direct supply of dilution air to the mask is interposed a subset that can be described as a "request" providing the functions of ambient air inspiration and instantaneous demand flow detection. This subassembly comprises a pressure sensor 28 in the mask. In the illustrated case, the cross section of the dilution air flow is delimited by an altimetric capsule 30 whose length increases when the pressure ambient temperature decreases and the end portion of an annular piston 32. piston is subject to the difference between the atmospheric pressure and the pressure in a chamber 34. An additional solenoid valve 36 makes it possible to connect the chamber 34 either to the atmosphere or to the power supply. oxygen under pressure. The solenoid valve 36 thus makes it possible to switch from one normal with dilution to a pure oxygen supply mode (so-called 100%). When the chamber 34 is connected to the atmosphere, a spring 38 keeps the piston in a position allowing the adjustment of the section of passage through the altimetry capsule 30. When the chamber is connected to the power supply, the piston is applied against the capsule. The piston 32 can also constitute the movable member of a slave control valve.

The box of part 10 also defines an expiration path having an exhalation valve 40. The shutter member of the valve represented is of a type commonly used at present to fill the dual function of intake pilot valve and exhaust valve. In the embodiment of FIG. 1, it simply acts as a valve exhalation providing the possibility of keeping the inside of the mask in overpressure compared to the ambient atmosphere by increasing the pressure prevailing in a chamber 42, limited by the element 40, above the ambient pressure.

In a first state, a solenoid valve 48 connects the chamber 42 to the atmosphere and in this case the expiration takes place as soon as the pressure in the mask exceeds the ambient pressure. In a second state, the solenoid valve 48 connects the chamber to the oxygen supply under pressure, via a flow restrictor 50. In this case, the pressure in the chamber 42 is established at the value set by a valve 46 spring loaded with closing.

The housing of part 10 carries, in the illustrated embodiment, means for inflating and deflating a pneumatic harness of mask. These means have a classic constitution and as a consequence do not will not be described in detail. They comprise a piston 52 which can be brought temporarily, using an ear 54 operated by the user of the mask, of the position where he is represented and where he makes the harness communicate with the atmosphere to a position where it makes the harness communicate with the oxygen supply 14. However, these means include in addition switch 56 controlled by the displacement of the ear 54 from its rest position, whose role will appear later.

Part 12 of the regulator, which is carried by the storage box of the mask, has a selector 58 movable in the direction of the arrows "f" and can be brought by the user in 3 positions.

In the position shown in FIG. 1, the selector 58 closes a switch 60 of normal mode N. In the other two positions, it closes respectively 100% mode switches and "Emergency" or E.

The switches are connected to an electronic circuit 62 which determines, depending on the chosen operating mode, the indicated cabin altitude by a sensor 64 and the instantaneous demand rate indicated by the sensor 28, the flow of oxygen to be supplied to the wearer of the mask. The map provides the appropriate electrical signals to the first solenoid valve 24.

In normal mode, the pressure sensor 28 provides the pressure of instantaneous demand at the outlet of the dilution air circuit in the mask. The circuit carries an electronic card, receives this signal as well as cabin altitude information to be taken into account from the sensor 64. The electronic card then determines the flow rate or quantity of oxygen at provide, using a family of stored reference curves holding account of the instantaneous demand rate and the cabin altitude, or a table to multiple inputs or even a real-time calculation from an algorithm stored.

The reference curves are based on the regulations that set the required breathing mixture concentration for the pilot in cabin altitude function.

In FIG. 3, the solid line curve shows the minimum value of the oxygen content required as a function of altitude. The dashed curve gives the maximum value. The reference curves will be chosen so that they are not never below the minimum curve. But thanks to the flexibility offered by the electronic order, it will be possible to be very close.

FIG. 4 shows, by way of example, two curves representing respectively the variation of the oxygen flow rate and the dilution air flow rate controlled by the solenoid valve 24 and the controlled opening valve altitude function, with a given value of the signal supplied by the sensor 28.

In 100% mode, that is when the wearer of the mask brings the one click to the right from the position shown in FIG. card 62 sends an electrical instruction to the solenoid valve 36. This causes pressurizing the chamber 34, applies the piston 32 against the capsule altimetry 30 and closes the dilution air inlet. The pressure sensor 28 detects the vacuum in the ambient air inlet circuit and provides the card 62 corresponding information. The card then determines the flow of oxygen to supply. The first solenoid valve 24 then provides the wearer with mask the calculated amount of oxygen.

When the carrier selects the "emergency" mode by moving the selector 28 further to the right, the card 62 issues a set to the valve 48. The solenoid valve then admits, in the chamber 42, a pressure which is limited by the valve 46. Usually, the overpressure established is of the order of 5 mbar. At the same time, the dilution air inlet is cut as in the previous case. The pressure sensor 28 sends still a signal to map 62 that determines the amount of oxygen to be supplied to reduce the pressure in the air inlet circuit to a value equal to valve calibration 46.

In the embodiment variant shown in FIG. corresponding to those of Figure 1 are designated by the same numbers of reference, the first valve 24a is placed in the housing of the box of mask storage. The regulator can then be viewed as comprising a control part, entirely carried by the box 12 and which allows the selection of the operating mode. A "request" part, placed in the housing mounted on the mask and which performs the functions of ambient air inspiration and detection of the call pressure. The third part, which provides the supplement of the required oxygen depending on the altitude and of the inspiratory request of the pilot, is this time in the box of the mask storage box.

In the device shown in FIG. 2, the supply control of the supplement of oxygen by the valve 24 a is completed by a tap controlled pneumatic 68 of known constitution, placed downstream of the valve 24 a. In a conventional manner, the piloted pneumatic valve 68 is controlled by the pressure prevailing in a flight chamber 70. The membrane 40, which this time plays the dual role of pilot valve and exhalation valve, controls the pressure in the control chamber 70.

The presence of the cock controlled in the embodiment of FIG. 2 allows to provide a mechanical control valve 72 controlled by the selector 58 for connecting the upstream to downstream of the solenoid valve 24 (a). So, in case of power supply failure, the wearer of the mask can immediately switch from a controlled mode to oxygen saving to a conventional mode to purely pneumatic operation.

Claims (4)

Oxygen regulating device for a carrier in a civil or military aircraft, and comprising: an oxygen supply circuit connecting an inlet of pressurized oxygen from a source to an admission of a breathing mask via a direct flow control valve (24, 24a), an electronic control circuit (62) capable of sending an electrical instruction to said control valve. Device according to claim 1, in which the electrical setpoint is depending in particular on cabin altitude or ambient pressure. Device according to one of the preceding claims, comprising a control valve (72) for connecting upstream to downstream of the valve of ordered. Device according to one of the preceding claims, characterized in that the oxygen supply circuit comprises an oxygen cylinder.

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