EP2539225B1 - Diving rebreather comprising a mouthpiece - Google Patents

Description

The invention relates to a rebreather with a mouthpiece which is connected via a inhalation hose and an exhalation hose to a breathing gas circuit, wherein at least one gas sensor for measuring the partial pressure of a respiratory gas component is arranged in the respiratory gas circuit.

WO 2008/080948 , which is considered to be the closest prior art, describes such a device.

One differentiates between open breathing devices, half-closed and closed rebreather devices.

For example, open diving equipment includes a breathing gas storage bottle filled with compressed air or other breathing gas mixture and a one or two-stage pressure reducer which reduces the pressure of the gas in the bottle to ambient pressure. The exhaled air is released into the surrounding water, but only a small part of the oxygen in the breathing gas is really consumed. Thus, only about 3% of the inhaled gas is actually consumed on the water surface, while at a depth of, for example, 20 meters by the increased by two bar ambient pressure only a third of this value, ie 1% of the oxygen of the inspired gas is consumed. Thus, for a dive to a depth of twenty meters, one hundred times as much breathing gas has to be carried along as it actually consumes.

Semi-closed and closed rebreathers are used to circumvent system-related low breathing efficiency of open diving equipment. These devices are breathed in a cycle. The exhaled air is purified in rebreathers by means of a CO ₂ absorber of carbon dioxide and re-enriched with oxygen. Furthermore, such devices are characterized by a one- or two-part counterlung, which can absorb the exhaled gas volume. With rebreathers, gas efficiency can be increased up to 100%.

While open diving equipment normally breathes a gas with breathable oxygen content, semi-closed rebreather devices determine the partial pressure of oxygen (pO ₂ ) in the circuit according to the amount of gas supplied and the metabolism of the diver. In electronically controlled closed devices, the oxygen partial pressure is kept at a certain level by means of a control loop. Electronically controlled closed rebreathers, for example, from the publications GB 2 404 593 A . US 2003/188744 A1 and WO 2005/107390 A2 known. In manually controlled closed rebreathers, the oxygen supply manually set by the diver and thus the oxygen partial pressure manually controlled. In an electronically controlled closed-circuit rebreather, oxygen is usually metered in with an electromagnetic control valve. This solenoid valve is usually housed in the housing of the carbon dioxide filter. The actual control loop is implemented in one or - for redundancy reasons - in several microcontrollers. The oxygen partial pressure of the breathing gas must be within certain limits in order to be breathable. Generally, 0.16 bar is considered the lower limit and 1.6 bar the upper limit. An oxygen partial pressure below or above these limits is classified as life-threatening. It can be seen that for rebreathers a continuous monitoring of the oxygen partial pressure is necessary. Closed units require pO ₂ sensors for manual and / or electronically controlled regulation of the oxygen partial pressure in the breathing gas circuit. As pO ₂ sensors usually electrochemical liquid electrolyte sensors are used, which must be calibrated before the dive on the surface with air or 100% O ₂ .

A properly functioning pO ₂ sensor for use in rebreathers has an output signal (current or voltage), which depends linearly only on the oxygen partial pressure in front of the membrane of the sensor.

• Nichtlinearität;
• Stromlimitierung: in diesem Fall wird der pO₂-Sensor ab einem bestimmten Sauerstoffpartialdruck nichtlinear da der Ausgangsstrom des Sensors (oder Ausgangsspannung) fehlerbedingt nicht über einen bestimmten Level ansteigen kann. Dies resultiert in zu niedrigen Sensorsignalen bei hohem Sauerstoffpartialdruck;
• Fehlerhafte Signale von einem oder mehreren Sensoren bzw. der Sensorsignalverarbeitung;
• Fehlerhafte Kalibrierung.

However, pO ₂ sensors designed as liquid electrolyte sensors are very error-prone. Typical errors that can occur are:

• Nonlinearity;
• Current limitation: in this case, the pO ₂ sensor becomes non-linear at a certain oxygen partial pressure because the output current of the sensor (or output voltage) can not rise above a certain level due to an error. This results in too low sensor signals at high oxygen partial pressure;
• Faulty signals from one or more sensors or the sensor signal processing;
• Incorrect calibration.

The error susceptibility of the pO ₂ sensors is attempted with the redundant use of pO ₂ sensors to counter. For example, three oxygen sensors are usually used in closed rebreathers. If one sensor fails and therefore its output signal differs from that of the other two, this is detected by a comparison of all three sensor signals with a "voting algorithm", and this sensor is no longer used to control the pO ₂ (see GB 2 404 593 A or WO 2004/112905 A1 ).

• Ausfall von zwei Sensoren, die jedoch ein gleiches Ausgangssignal haben;
• gleiche Nichtlinearität von mindestens zwei Sensoren (> = zwei Sensoren aus der gleichen Produktionscharge, gleiches Alter, gleiche Bedingungen, ...);
• gleiche Stromlimitierung von mindestens zwei Sensoren.

A faulty sensor can thus be determined. However, this method fails with the following errors:

• Failure of two sensors, but with the same output;
• same nonlinearity of at least two sensors (> = two sensors from the same production lot, same age, same conditions, ...);
• same current limitation of at least two sensors.

An alternative is in WO 2008/080948 A2 described. A calibration / validation device allows the flow of an oxygen sensor with a gas of known composition. Thus, a sensor can be easily checked for correct function.

• Kurze Lebensdauer von maximal ca. 1.5 Jahren;
• Können fehlerhafte Signale bei hoher Luftfeuchtigkeit liefern (Kondensation auf der Sensormembran);
• Elektrolyt kann aus dem Sensorgehäuse lecken;
• Lange Ansprechzeiten (t90) von typisch 6 s;
• Relativ große Abmessungen;
• Die relativ lange Ansprechzeit macht eine Regelung des Sauerstoffpartialdruckes relativ schwierig. In einem geschlossenen Kreislauftauchgerät wird üblicherweise der Sauerstoffpartialdruck mit Sauerstoffpartialdrucksensoren gemessen und sodann mit Hilfe eines Regelkreises (meistens mit einem Mikrocontroller) ein elektromagnetisches Steuerventil angesteuert, mit welchem Sauerstoff aus einer Vorratsflasche dem Kreislauf zugeführt wird. Im schlimmsten Fall kann dies kurzzeitig zu hohen Sauerstoffpartialdruckspitzen im Kreislauf führen, die als lebensbedrohend angesehen werden müssen, jedoch mit den herkömmlichen Sensoren aufgrund deren langer Ansprechzeit nicht erkannt werden, da die lange Ansprechzeit eine Mittelung des Signals bewirkt.

In addition to the susceptibility to errors, O ₂ liquid-electrolyte sensors also have further disadvantages:

• Short life of a maximum of about 1.5 years;
• May give erroneous signals at high humidity (condensation on the sensor membrane);
• Electrolyte can leak from the sensor housing;
• Long response times (t90) of typically 6 s;
• Relatively large dimensions;
• The relatively long response time makes regulation of the oxygen partial pressure relatively difficult. In a closed rebreather usually the oxygen partial pressure is measured with oxygen partial pressure sensors and then with the aid of a control circuit (usually with a microcontroller) an electromagnetic control valve is activated, with which oxygen is supplied from a supply bottle to the circuit. In the worst case, this can temporarily lead to high oxygen partial pressure spikes in the circuit, which must be regarded as life-threatening, but are not recognized with the conventional sensors due to their long response time, since the long response time causes an averaging of the signal.

• Atemkalk ist defekt
• Maximale Absorptionskapazität ist erreicht, es kann kein weiters Kohlendioxid aufgenommen werden;
• Der Absorber ist zu kalt und die chemische Reaktion findet nur ungenügend statt;
• Wasser ist im Kreislauf eingedrungen und dadurch wurde der Atemkalk unbrauchbar;
• Richtungsventile im Mundstück sind defekt - es kommt zu Pendelatmung und der Kohlendioxidfilter wird nicht durchströmt, somit kann kein Kohlendioxid absorbiert werden.

In a rebreather, a carbon dioxide absorber (chemical filter, soda lime, carbon dioxide filter, scrubber) absorbs the exhaled carbon dioxide. A proper function of the carbon dioxide absorber is vital, since with an increase in the carbon dioxide content in the circulation threatens carbon dioxide poisoning, which in turn is classified as life-threatening. The following errors can occur:

• Soda lime is defective
• Maximum absorption capacity is reached, no further carbon dioxide can be absorbed;
• The absorber is too cold and the chemical reaction is insufficient;
• Water has entered the circulation and thus the soda lime has become unusable;
• Directional valves in the mouthpiece are defective - it comes to pendulum breathing and the carbon dioxide filter is not flowed through, so no carbon dioxide can be absorbed.

Many projects have been developing a CO ₂ sensor for rebreathers to detect a carbon dioxide filter malfunction and / or an increase in CO ₂ in the circuit. Optical CO ₂ sensors are usually based on absorption of infrared light. However, this method is not very reliable due to the high humidity (up to 100% condensing) in a rebreather. It is known to increase the reliability in front of the measuring cell of the infrared CO ₂ sensor to arrange a moisture barrier or hydrophobic membrane. Another way to increase the reliability of such CO ₂ sensors, the sensors / sensor element is to increase to a temperature greater than the gas temperature in the rebreather, to preclude condensation. Furthermore, to check the function of the carbon dioxide absorber, the temperature of the carbon dioxide filter can be measured ( US 2003/074154 A1 ).

The DE 10 2007 039 124 A1 describes a device and a method for controlling and / or regulating a training and / or regulation of a training and / or rehabilitation unit. In addition to a training and rehabilitation unit, a microcontroller and a brake or resistance arrangement, this device contains a sensor unit with a heatable electrochemical solid electrolyte sensor for determining oxygen concentration and another heatable electrochemical solid electrolyte sensor for determining the concentration of carbon dioxide.

In the article " Solid State Electrolyte Sensors for the Determination of Oxygen, Carbon Dioxide, and Total Flow Rates Associated to Respiratory Human Subjects, edited by S. Fasoulas, Executive Summary to the ESTEC Contract No. 15450/01 / NL / JS, CCN 1, 2,3, Report No. ILR-RSN P 06-07, 13th October 2006 (can be found online at http://www.ibtk.de/project/rss/PR03-FR-Exec-Sum_17102006.pdf ) the use of solid electrolytes for the determination of O ₂ and CO ₂ concentrations as well as for other applications is discussed and presented. Among other things, from this publication, an arrangement with built-in a pipe O ₂ - and CO ₂ sensors is known, wherein the pipe section is connected via a filter with a breathing mask. Thus, inhaling and exhaling through the same blank (Figure 35). The sensor electronics are housed in a separate housing.

A rebreather usually has an inhalation and exhalation hose. In between, the mouthpiece is mounted, in which two directional valves are arranged. The main focus in the construction of rebreathers is, among other things, a construction of a mouthpiece in which the so-called dead space, which is understood as meaning the space between the directional valves and the bite piece, is minimized. This is important because otherwise there is the risk that the CO ₂ content in the dead space increases. This is especially a problem when the diver is breathing very shallow. An integration of a piece of pipe, as described in said article, is detrimental or an additional risk factor in a diving device, because this would increase the dead space, especially taking into account that in cross-section diving devices, the cross sections of gas supply and discharge approx. 15 cm ² should be in order to allow even at greater depths a minimum work of breathing (WOB = work).

The JP 2005 350 282 A , the US 5,746,806 A , as well as the US 5 071 453 A essentially disclose oxygen concentrators which also employ, among other things, a zirconia solid state electrolyte sensor.

It is the object of the invention to avoid said sources of error in the partial pressure measurement of gas constituents in the respiratory gas. Furthermore, it is an object of the invention to design the measuring system so that mechanical errors such as incorrect directional valves are detected in the mouthpiece and a robust and fault-prone design is achieved.

According to the invention this object is achieved in that the gas sensor is designed as a solid electrolyte sensor, wherein at least one solid electrolyte sensor is arranged in the mouthpiece. At least two directional valves may be arranged in the mouthpiece, wherein preferably at least one gas sensor is arranged between the two directional valves. This should be the mouthpiece be designed so that the dead space between the directional valves and the bite piece is minimized and yet large cable cross-sections are met. The solid electrolytic sensor can be incorporated as O ₂ - may be formed and / or CO ₂ as a gas sensor.

Solid state electrolyte sensors are based on special materials that are conductive to gas ions. Normally, however, these materials are conductive only at elevated temperatures (typically 500 ° C - 700 ° C). Typical materials include zirconia and ceria for oxygen and nasicon for CO ₂ .

Potentiometric solid electrolyte sensors for oxygen have been known for a long time, and find application in engine controls (lambda sensor) or in industrial combustion controls, among others.

Conventional sensors such as e.g. used in a car, but have the disadvantage that they are relatively large, therefore, require a high electrical heating power (> 10 watts) and a reference measuring chamber with a reference gas is necessary (potentiometric sensors, Nernst potential). These disadvantages have not permitted the use of these sensors in rebreathers until today.

Miniaturized gas sensors are used, among other things, for in-situ and bypass measurements of O _x , CO _x , H ₂ , C _x H _y , NO _x in medical and environmental technology, eg in the performance diagnostics of astronauts or for residual gas analysis in space , (see http://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_maschinenwesen/ilr/rsn).

Thick-film miniature solid-state electrolyte sensors have the advantage of a long service life and a very fast response time. The actual sensor elements are available in the size 2.5 x 2.5 x 2 mm ³ and can be easily integrated into a rebreather. Due to the small design only low heat outputs (1 - 2 watts) are required, which allows conventional batteries or rechargeable batteries to operate for several hours.

The high operating temperature prevents condensation-related disturbances. The fast response time allows precise control of the oxygen partial pressure. The high response speed of less than 100 ms even allows to determine the heart rate, as the pO ₂ / pCO ₂ signal of the exhaled air is modulated with the heart rate.

The small dimensions allow integration of the gas sensors directly in the mouthpiece. Thus, the oxygen partial pressure of inhaled and exhaled gas can be detected separately. Favorable placement in the gas stream can also be used with these solid-state electrolyte sensors to measure the mass flow of the respiratory gases and thus the minute volume of the diver and the respiratory rate be inferred. The high temporal resolution of the sensors allows a high-precision determination of small and short-term oxygen partial pressure changes.

By recording minute volume and respiratory rate, the load on the diver can be recorded and this, in turn, can be used as a factor influencing the decompression calculation.

• Sehr schnelle Ansprechzeit < 100 ms;
• Betriebstemperatur 650°C (O₂) und 550°C (CO₂). Durch die hohe Betriebstemperatur können Probleme mit hoher/kondensierender Luftfeuchtigkeit ausgeschlossen werden;
• O₂-Sensor: unbegrenzte Lebensdauer;
• CO₂-Sensor: ∼ 2000 Betriebsstunden;
• Der O₂-Sensor ist ein amperometrischer Sensor - somit ist keine Referenzmesskammer nötig;
• Im CO₂-Sensor ist eine Festelektrolytreferenz integriert, so benötigt auch dieser keine Referenzkammer;
• Niedrige Betriebskosten;
• Sensoren sind sehr klein (eigentliches Sensorelement ∼ 4mm²);
• Die hohe Ansprechgeschwindigkeit erlaubt sogar die Herzfrequenz mitzubestimmen, da das pO₂/pCO₂ Signal der ausgeatmeten Luft mit der Herzfrequenz moduliert ist.

Planar miniature solid-state electrolyte sensors for the partial pressure measurement of CO ₂ and O ₂ thus have the following properties:

• Very fast response time <100 ms;
• Operating temperature 650 ° C (O ₂ ) and 550 ° C (CO ₂ ). Due to the high operating temperature problems with high / condensing humidity can be excluded;
• O ₂ sensor: unlimited life;
• CO ₂ sensor: ~ 2000 operating hours;
• The O ₂ sensor is an amperometric sensor - so no reference measuring chamber is needed;
• In the CO ₂ sensor, a solid electrolyte reference is integrated, so this also requires no reference chamber;
• Low operating costs;
• Sensors are very small (actual sensor element ~ 4mm ² );
• The high response rate even allows to determine the heart rate, as the pO ₂ / pCO ₂ signal of the exhaled air is modulated with the heart rate.

• Hohe Betriebssicherheit, da die Sensoren sehr robust und fehlerresistent sind;
• Da die Sensoren sehr klein sind, lassen sie sich auch direkt in dem Mundstück von einem Kreislauftauchgerät integrieren;
• Da die Sensoren eine sehr kurze Ansprechzeit haben (< 100 ms) lassen sich
  • o der Sauerstoffpartialdruck im System besser und genauer steuern;
  • o Unterschiede in der Gaszusammensetzung von eingeatmetem und ausgeatmetem Gas messen (bei Integration im Mundstück);
  • o Dies erlaubt Rückschlüsse auf den Sauerstoffmetabolismus des Tauchers.
• Da die Sensoren auf hoher Temperatur gehalten werden, können diese als Gas-Massenflussmesser eingesetzt werden. Durch geeignete Platzierung der Sensoren im Gasfluss, kann der Gasstrom gemessen werden (Ein- und Ausatemvolumen, Minutenvolumen), dies erlaubt:
  • o Rückschluss auf Aktivität des Tauchers (Stress, hohe körperliche Belastung, ...);
  • o Feststellung, ob der Taucher überhaupt atmet, und wie schnell - was wiederum als Eingangsparameter für die Steuerung verwendet werden kann.
• Mit einem vorzugsweise zwischen den Richtungsventilen platzierten CO₂-Sensor kann folgendes überprüft werden
  • o Korrekte Funktion des CO₂-Filters;
  • o Korrekte Funktion der Richtungsventile im Kreislauftauchgerät (falls die Richtungsventile beschädigt sind, kann dies schnell zu einem lokalen CO₂ Anstieg führen (CO_2--buildup);
  • o Rückschluss auf den Metabolismus des Tauchers (hohe körperliche Belastungen, Stress, ...);
  • o Überprüfung des Sauerstoffsensors bzw. des Kohlendioxidsensors: im Normalfall sollte die Differenz des Sauerstoffpartialdrucks des ein- und des ausgeatmeten Gases in etwa der Differenz des Kohlendioxidpartialdruckes entsprechen.

Application of an O ₂ and a CO ₂ solid state electrolyte sensor in a rebreather results in the following advantages:

• High operational safety, as the sensors are very robust and error-resistant;
• Since the sensors are very small, they can also be integrated directly into the mouthpiece of a rebreather;
• Since the sensors have a very short response time (<100 ms) can be
  • o control the oxygen partial pressure in the system better and more accurately;
  • o measure differences in the gas composition of inhaled and exhaled gas (when integrated in the mouthpiece);
  • o This allows conclusions about the oxygen metabolism of the diver.
• Since the sensors are kept at high temperature, they can be used as a gas mass flow meter. By appropriate placement of the sensors in the gas flow, the gas flow can be measured (inhalation and exhalation volume, minute volume), allowing:
  • o conclusion on activity of the diver (stress, high physical stress, ...);
  • o Determining if the diver is breathing at all and how fast - which in turn can be used as an input parameter to the controller.
• With a preferably placed between the directional valves CO ₂ sensor, the following can be checked
  • o Correct function of the CO ₂ filter;
  • o Correct operation of the directional valves in the rebreather (if the directional valves are damaged, this can quickly lead to a local CO ₂ increase (CO _2- buildup);
  • o conclusions about the metabolism of the diver (high physical stress, stress, ...);
  • o Checking the oxygen sensor or the carbon dioxide sensor: Normally, the difference in the oxygen partial pressure of the inhaled and expired gases should correspond approximately to the difference in the partial pressure of carbon dioxide.

• o eine optimierte Regelung der Sauerstoffzuführung;
• o eine Erfassung von physiologischen Daten (Metabolismus, Atemzugsvolumen, Minutenvolumen, Atemfrequenz, O₂-Gehalt in Ein-und Ausatemgas, CO₂ im Ausatemgas) - dies kann
  • ■ zur Überprüfung der Sauerstoffregelung genutzt werden;
  • ■ Einfluss finden in der Dekompressionsberechnung (wichtiger Punkt);
• o erhöhte Sicherheit des Systems durch unterschiedliche Sensorsysteme (O₂-, CO₂- und Massenflusssensor)

The multitude of advantages allows so

• o an optimized control of the oxygen supply;
• o a collection of physiological data (metabolism, tidal volume, minute volume, respiratory rate, O ₂ content in inhaled and exhaled gas, CO ₂ in exhaled gas) - this can
  • ■ be used to check the oxygen control;
  • ■ find influence in the decompression calculation (important point);
• o Increased safety of the system due to different sensor systems (O ₂ , CO ₂ and mass flow sensor)

To control and read the sensors electronic circuits are necessary. These usually consist of a microcontroller that takes over the heating control and an analogue circuit, which typically consists of amplification and analogue filters. With today's technology, such a circuit can be highly miniaturized, so that the entire electronics requires less than 1 - 2 cm ³ space.

Part of the invention is the integration of electronics and sensors directly in the mouthpiece. Long sensor cables (as described in the article by S. Fasoulas) can lead to measurement errors if there are electrical interference fields. Underwater, this is usually not the case, but rebreathers are being prepared on the surface. Electromagnetic interference due to, for example, radio or a poorly suppressed motor can - especially when long leads are used - lead to measurement errors. This is especially problematic if these measurement errors occur during a device test or a calibration, since in this case a faulty O _{2 control} can be the result - a circumstance that can be classified as life-threatening. Problems of this kind have already led to accidents with rebreathers in the past. By integrating the electronics directly next to the sensors in the mouthpiece, such sources of error can be minimized.

Using miniaturized solenoid valves, the oxygen supply control valve in the breathing circuit can also be integrated directly into the mouthpiece. Thus, once again the compactness and robustness can be further increased, since sources of error such as cables to the solenoid valve, which lead through the water, omitted.

Together with a miniaturized electronic control unit, the complete control circuit of the rebreather can thus be integrated in the mouthpiece.

• o keine langen Kabel und dadurch verursachte Signalverfälschungen, da Sensoren, Magnetventil, Elektronik und Stromversorgung (Batterie) direkt nebeneinander integriert sind;
• o robustere Bauweise und so erhöhte Sicherheit;
• o kostengünstige Bauweise;
• o das Mundstück beinhaltet die gesamte Elektronik. Kreislauftauchgeräte ohne elektronischer Steuerung können einfach aufgerüstet werden, indem das ursprüngliche Mundstück mit dem vollintegrierten Mundstück ersetzt wird

The integration of the complete control electronics and the control valve in the mouthpiece offers numerous advantages:

• o no long cables and signal distortions caused by them, as sensors, solenoid valve, electronics and power supply (battery) are integrated directly next to each other;
• o more robust construction and thus increased safety;
• o cost-effective construction;
• o The mouthpiece contains all the electronics. Rebreather units without electronic controls can be easily upgraded by replacing the original mouthpiece with the fully integrated mouthpiece

• Die Sensoren werden hinter einer hydrophoben Membran angeordnet, welche ein Endringen von Wasser verhindert.
• Das Mundstück ist mit einer Vorrichtung versehen, mit der - falls das Mundstück unter Wasser aus dem Mund genommen wird - der Raum zwischen den Richtungsventilen gegen das Bissstück abgedichtet wird.
• Die Elektronik überwacht kontinuierlich die Temperatur des Sensors. Falls diese plötzlich abfällt, obwohl der Heizstrom konstant bleibt, ist dies ein Hinweist dafür, dass der Sensor in Kontakt mit Wasser ist. Als Folgemaßnahme wird die Heizleistung minimiert, um eine Überlastung des Heizers zu vermeiden. Insbesondere wird die Spannungsversorgung des Heizers auf kleiner 1 Volt begrenzt, um Elektrolyse zu vermeiden. Falls die Sensortemperatur anschließend wieder größer als 100°C beträgt, kann davon ausgegangen werden, dass das Wasser verdunstet ist und der normale Betrieb kann wieder aufgenommen werden.

The solid-state electrolyte sensors are, as already described, electrically heated. If the mouthpiece is flooded, it may happen that the sensors are exposed to the water. Several measures are conceivable to protect the sensors:

• The sensors are placed behind a hydrophobic membrane, which prevents the penetration of water.
• The mouthpiece is provided with a device with which - if the mouthpiece is taken under water from the mouth - the space between the directional valves is sealed against the bite piece.
• The electronics continuously monitor the temperature of the sensor. If this drops suddenly, although the heating current remains constant, this is an indication that the sensor is in contact with water. As a consequence, the heating power is minimized to avoid overloading the heater. In particular, the voltage supply of the heater is limited to less than 1 volt to avoid electrolysis. If the sensor temperature is then greater than 100 ° C again, it can be assumed that the water has evaporated and normal operation can be resumed.

Often, a rebreather tip is attached to a full-face mask. This is particularly often preferred by emergency services, as full-face masks bring additional security. For example, in the case of powerlessness, a gas supply remains secure. This is special for divers important, because a fainting can cause the mouthpiece falls out of the mouth and thus the gas supply is interrupted.

Fig. 1

ein bekanntes Kreislauftauchgerät; und

Fig. 2

einen Teil eines erfindungsgemäßes Kreislauftauchgerätes.

The invention will be explained in more detail below with reference to FIGS. Show it:

Fig. 1

a known rebreather; and

Fig. 2

a part of an inventive rebreather.

Fig. 1 shows a closed rebreather according to the prior art. The diver exhales through the bite piece 19 connected to the mouthpiece 1 via the exhalation hose 2 into the exhalation counterlung 4. In the CO ₂ filter 7 ("scrubber"), carbon dioxide is chemically absorbed from the exhaled air. The breathing gas then passes into the inhalation counter lung 5. About the bite piece 19 of the mouthpiece 1 and the inhalation tube 3, the breathing gas is inhaled again. To replace the used oxygen, fresh O ₂ gas is supplied to the breathing gas circuit from an oxygen storage bottle 11 via an electromagnetic control valve 9, which is usually housed in the housing of the CO ₂ filter 7. A pressure reducer 12 reduces the cylinder pressure to a pressure of typically 7 - 10 bar. The storage bottle 11 contains pure oxygen O ₂ . In addition to the electromagnetic control valve 9, the control circuit also has a microcontroller 10 and one to four oxygen sensors 8, via which the oxygen partial pressure pO ₂ in the breathing gas circuit is measured. Dive relevant data are displayed on a display 15. If the oxygen partial pressure falls below a certain value, pure oxygen O _{2 is added to} the respiratory gas cycle via the electromagnetic control valve 9. When diving, the breathing gas is compressed in the breathing gas circulation. To compensate for the pressure-related loss of volume, diluent gas from a supply bottle 13 is supplied to the breathing gas circuit 26 via a manual valve 16 or an automatic valve. By means of the two pressure reducers 12, 14, the cylinder pressure is reduced to typically 8-10 bar above atmospheric pressure. Excess gas can escape through a pressure relief valve 6.

Fig. 2 shows a simple embodiment of the invention. The embodiment formed as a mouthpiece integrated mouthpiece 1 is connected via a breathing tube 3 and an exhalation 2 to the breathing gas circuit 26. The two directional valves - inhalation valve 18 and exhalation valve 17 - specify the gas flow direction. With 19 is the actual rubber bite piece, which holds the diver with his teeth. The O ₂ sensor 20 and the CO ₂ sensor 21 are formed as solid electrolyte sensors and mounted in the cavity of the mouthpiece 1 between the directional valves 17, 18. By means of a formed by a miniature solenoid valve control valve 23, which the control valve 9 from Fig. 1 can be replaced from an in Fig. 2 unrecognizable oxygen storage bottle and an oxygen supply line 24 oxygen via an opening 27 to the breathing gas circuit 26 are supplied. The feed into the breathing gas circuit 26 takes place after the exhalation valve 17 in order to guarantee a good mixing and at the same time to avoid short-term peak increases in the oxygen partial pressure in the inhaled gas. The control of the control valve 23 via an electronic control unit 22 via a waterproof cable 25, a display unit and an external battery power can be connected. The electronic control unit 22 and the control valve 23 are water and pressure-tight integrated in the mouthpiece 1.

In the context of the invention, further options may be provided. Thus, (a) a disc or barrel-like closure for the bit may be incorporated into the mouthpiece 1 in the event that the bit 19 is removed from the mouth by the diver. Furthermore, it is conceivable to integrate a switching roller in the mouthpiece 1, which allows a switch from closed circuit to open circuit (b). In this case, a so-called second stage (low-pressure stage) of an open dipping system is expediently integrated into the mouthpiece 1. The second stage can also act as an auto diluent control valve in closed mode. In both cases, however, the mouthpiece is designed so that when the bite piece is closed in case (a) or in open mode in case (b), the sensors are protected between the directional valves of water. In case (a), this is easy to do because the disc or roller-type closure seals the space between the directional valves from the bit, and so automatically the sensors are also protected from water.

Claims (12)

1. Rebreather with a mouthpiece (1) which is connected to a respiratory gas circulation via an inhalation tube (3) and an exhalation tube (2),
   wherein at least one gas sensor for measuring the partial pressure of a respiratory gas component is arranged in the respiratory gas circulation (26),
   characterized in that
   the gas sensor is formed as a solid state electrolyte sensor, wherein at least one solid state electrolyte sensor is arranged in the mouthpiece (1).
2. Rebreather according to claim 1, characterized in that the mouthpiece comprises at least two direction valves (17, 18), wherein preferably at least one gas sensor is arranged between the two direction valves (17, 18).
3. Rebreather according to claim 1 or 2, characterized in that at least one solid state electrolyte sensor is formed as an O₂ sensor (20).
4. Rebreather according to one of the claims 1 to 3, characterized in that at least one solid state electrolyte sensor is formed as a CO₂ sensor (21).
5. Rebreather according to one of the claims 1 to 4, with at least one oxygen supply conduit (24) ending into the respiratory gas circulation (26) via an electrical control valve (23), characterized in that the electrical control valve (23), which is preferably formed as a miniature magnetic valve, is arranged in the mouthpiece (1).
6. Rebreather according to claim 5, characterized in that the oxygen supply conduit (24) is ending into the respiratory gas circulation in the region of the mouthpiece (1), preferably into the exhalation tube (2) downstream of an exhalation valve (17).
7. Rebreather according to one of the claims 1 to 6, characterized in that an electronic control unit (22) connected to the gas sensor and/or to the electrical control valve (23) is integrated in the mouthpiece (1).
8. Rebreather according to claim 7, characterized in that the electronic control unit (22) is connected to an external display unit and/or an external energy source.
9. Rebreather according to one of the claims 1 to 8, characterized in that at least one battery for current supply of the electronic control unit (22) is arranged in the mouthpiece (1).
10. Rebreather according to one of the claims 1 to 9, characterized in that the mouthpiece (1) is connected to a full face mask.
11. Rebreather according to one of the claims 1 to 10, characterized in that at least one solid state electrolyte sensor is protected against water by a hydrophobic membrane.
12. Rebreather according to one of the claims 1 to 11, characterized in that the mouthpiece comprises a bite piece and that the gas sensor in the mouthpiece is sealable against the bite piece and protectable against water by an apparatus, preferably a disc-type or a roller-type closure.

Images