WO2020156623A1

WO2020156623A1 - Non-magnetic diving rebreather

Info

Publication number: WO2020156623A1
Application number: PCT/DK2020/050025
Authority: WO
Inventors: Jan Petersen
Original assignee: Jj-Ccr Machining Aps
Priority date: 2019-01-30
Filing date: 2020-01-29
Publication date: 2020-08-06

Abstract

Closed circuit mixed gas diving rebreather which comprises -a gas loop, for one-directional circulation of the gas,and comprising -one or more counterlungs, -a scrubber container, which contains a carbon dioxide scrubber, - a gas-transferring member, - at least one hose, said rebreather further comprises -a first pressure container, which is connected to the gas loop via a first pressure regulator, -a microcontroller, - at least one oxygen sensor, -a power source, -a first valve for regulating the oxygen gas supply to the gas loop, -a piezoelectric actuator, which actuates the first valve, which piezoelectric actuator is non-magnetic. The first valve is a non-magnetic on-off valve. The first pressure container is made from a non-magnetic material. The diving rebreather further comprises -a second pressure container, which is made from a non-magnetic material, and which is connected to the gas loop via a second pressure regulator, -a second valve which is non-magnetic, -a non-magnetic support frame.

Description

Non-magnetic diving rebreather

Field of the Invention

The present invention relates to a closed circuit mixed gas diving rebreather, which supplies a diver with a gas with a well-defined partial pressure of oxygen during div ing, which rebreather comprises

- a gas loop, for one-directional circulation of the gas, and comprising

- one or more counterlungs,

- a scrubber container, which contains a carbon dioxide scrubber,

-a gas-transferring member chosen between a mouth piece or a facemask ar ranged for transferring the gas to the diver,

- at least one hose, which is connected with the scrubber container, the coun- terloung and the gas-transferring member,

- said carbon dioxide scrubber removes carbon dioxide from the gas, said rebreather further comprises

- a first pressure container, which contains oxygen gas and which first pressure con tainer is connected to the gas loop via a first pressure regulator,

- a microcontroller, which regulates an oxygen gas supply to the gas loop,

- at least one oxygen sensor, which measures the oxygen content of the gas in the gas loop in a position between the carbon dioxide scrubber and the gas-transferring mem ber,

- a power source, for powering the microcontroller,

- a first valve for regulating the oxygen gas supply to the gas loop,

- a piezoelectric actuator, which actuates the first valve, which piezoelectric actuator is non-magnetic.

A further aspect of the invention is the use of a non-magnetic rebreather for diving at water depths deeper than 10 meters.

Background of the Invention

It is known to use rebreathers for diving, which create a circulatory gas loop such that the diver breathes the gas that was previously exhaled. In the gas loop there is placed a carbon dioxide scrubber, which is a substance which removes carbon dioxide from the exhaled gas by chemically binding carbon dioxide. Thus, the partial pressure of carbon dioxide in the gas loop is reduced. In the present application we refer to this as filtering. The carbon dioxide scrubber can be a mixture of sodium hydroxide or calcium hydroxide, for example Sofnolime. After filtering by the carbon dioxide scrubber, the gas is then inhaled again by the diver. If necessary, additional oxygen is supplied to the gas from a pressurised oxygen source to keep the partial pressure of the oxygen in a range suitable for the diver.

The function of a diving rebreather is to keep the oxygen partial pressure of the gas at a level suitable for the diver while minimising the consumption of the attached gas source or gas sources. A suitable partial pressure of oxygen for diving with a diving rebreather is typically a partial pressure of 1.0 - 1.3 bar with an upper limit of 1.6 bar and a lower limit of 0.4 bar for recreational use. In military diving, the upper limit can be up to 1.8 bar.

Too low a partial pressure of oxygen in the gas leads to dizziness and eventually to unconsciousness and drowning. Too high a partial pressure of oxygen in the gas leads to oxygen toxicity, which can lead to cramp seizures.

Diving rebreathers have a number of advantages. An advantage of rebreathers is that longer dives can be performed due to efficient re use of the gas in the rebreather.

Furthermore, no bubble trail is caused by closed loop rebreathers. Bubble trails are unwanted in recreational diving where it can scare marine wildlife or fill cavities such as ship wrecks or caves with air. In military operations, bubble trails are unwanted due to the often stealth nature of operations. For military use, the radiation of magnetic fields is considered troublesome, since magnetic field variations for example can set off sea mines. Therefore, a need for non magnetic diving rebreathers exists. From US 5,758,641 is known a diving rebreather of the type described in the introduc tion, comprising an oxygen pressure tank, a carbon dioxide scrubber for filtering car bon dioxide from gas, and a continuously variable valve, a pressure regulator, and a rebreather gas delivery device. The continuous variable valve is actuated by a reversi ble rotary motor which requires gears. The reversible rotary motor is a bi-directional bi-phase piezoelectric motor without an external magnetic field.

Non-magnetic diving rebreathers according to the state-of-the art have a number of drawbacks. They are limited to having only an oxygen source, and thus can only be used for div ing inwater depths of up to approx. 10 meters. At deeper diving depths, oxygen toxici ty as described above sets in. Many applications, such as disabling of sea mines, re quire a diving depth greater than 10 meters. Thus, a need for providing a non magnetic diving rebreather capable of diving at deeper water depths exists.

Furthermore, the regulation of a continuously variable valve is complex. This increas es the amount of potential errors which can occur during operation and reduces relia bility. Also, gears are error-prone, especially in harsh environments such as underwa ter marine applications.

Furthermore, in case of a failure of the pressure regulator or the continuously variable valve, overpressure can pass through the continuously variable valve into the re breather gas delivery device, which immediately renders the diving rebreather unusa ble and thus leads to drowning of the diver.

In case of a failure of the pressure regulator, the continuous variable valve needs to be closed to avoid overpressure or high partial pressure of oxygen in the gas loop which would render the rebreather unusable for the diver. Closing a continuous variable valve with a rotary motor connected with gears can be too slow to avoid build-up of overpressure in the gas loop. Hence, there exists a need for providing a non-magnetic diving rebreather with a faster control of the valve.

Another way of addressing this failure is to provide a normal scuba-system. This is suggested in W02009058080, wherein a mouthpiece is provided with electronics, such that in case of failure of the CCR system, it will automatically switch to the scu ba system. This mouthpiece is operable with any type of CCR system as it monitors the oxygen content coming to the mouthpiece, and in case of failure, the sensor will activate a valve construction allowing for continued diving based on the traditional scuba system.

There exists a need for providing a non-magnetic diving rebreather with more reliable operation.

There exists a need for providing a non-magnetic diving rebreather with increased safety for the diver.

There exists a need for providing a non-magnetic diving rebreather with a more sim ple control of the valve and/or partial pressure of the oxygen in the gas loop.

There exists a need for providing a non-magnetic diving rebreather with a more pre cise control of the partial oxygen pressure in the gas loop.

Furthermore, it is important to distinguish between two very distinct types of re breathers. In the art, it is widely recognised that there are basically two very different types of rebreathers. A first type is manual or mechanical rebreathers - often referred to as mCCR rebreathers. A second type is electronic rebreathers- often referred to as eCCR.

“CCR” is short for closed circuit rebreathers.

Understanding the difference is important in order to appreciate the present invention in its correct light.

mCCR - manual or mechanical rebreathers - are based on the fundamental principle of closed circuit diving: human metabolism consumes a fixed amount of oxygen (at con stant effort), which is about 1 liter per minute. A diver with a 31 tank filled with oxy- gen at 200 bar can - in theory - spend 10 hours under water. In fact, oxygen is "wast ed" during ascend and some other procedures, but all in all, very little oxygen is used. Furthermore, the depth does not affect the oxygen consumption. So what is needed is the system providing a fixed amount of oxygen to the breathing loop - exactly as much as is metabolized. CMF (Constant Mass Flow) is such a system, providing a fixed oxygen flow to the loop by a constant flow orifice. In ideal conditions (during relaxed swimming), the amount of oxygen provided by CMF is the same as the amount metabolized by the diver, which ensures/requires a fixed amount of oxygen in the breathing loop. At higher effort and during ascend, the diver has to add more oxy- gen to the loop, using a manual inhalation valve, to keep or provide the required amount of oxygen. The advantages of mCCR lie in the simple construction and rela tively small quantity of possible failure sources. These units do not have computers, electrovalves and other elements susceptible to failure. (They may be provided with very basic dive computers, but not in the sense of being computer operated or con- trolled operation). Basically, it is just an orifice (a hole of microscopic diameter) providing oxygen to the system regardless of the other elements. A drawback of this solution is the need for constant monitoring of pp02 and manual "refilling" of the oxygen content/concentration to the setpoint, which - in stressful situations and during ascend - significantly increases the risk of hypoxia (too small amount of oxygen in the mixture). eCCR - electronic CCR - is a system equipped with a solenoid, an electrovalve which opens on demand, adding oxygen to the breathing loop. Electronic rebreathers are controlled by a computer connected to oxygen sensors, using a special algorithm to maintain the oxygen setpoint in the breathing gas according to predefined parameters. For example if, during a dive, breathing the gas with an oxygen partial pressure at 1.3 bar is wanted - that is what is called a set-point. After correct setup, the computer is monitoring pp02 and as needed opens the solenoid (and thereby the electrovalve) to add oxygen in an amount providing pp02 of 1.3 bar. The advantage of this system is convenience - the diver does not have to manually maintain fixed pp02 in the breath ing loop - the computer does it for him.

The present invention is a rebreather of the eCCR type. Object of the Invention

The object of the invention is to provide a diving rebreather which addresses the above mentioned drawbacks and fulfils the above mentioned needs. It is an object of the invention to provide a non-magnetic diving rebreather, which can be used at water depths deeper than 10 meters.

It is an object of the invention to provide a non-magnetic diving rebreather with a more reliable operation than what is known in state of the art.

It is an object of the invention to provide a non-magnetic diving rebreather with a simpler and faster control of the valves.

Description of the Invention

This is achieved with a diving rebreather of the type described in the introduction and in the preamble of claim 1, which is peculiar in that

the electronic closed circuit mixed gas diving rebreather further comprises,

- a piezoelectric actuator, which actuates the first valve, which piezoelectric actuator is non-magnetic,

- that the first valve is a non-magnetic on-off valve,

that the first pressure container is made from a non-magnetic material, and

- that the diving rebreather further comprises

- a second pressure container, which contains a diluent gas, which second pressure container is made from a non-magnetic material, and which second pressure container is connected to the gas loop via a second pressure regulator,

- a second valve for regulating the diluent gas supply to the gas loop, and which sec ond valve is non-magnetic, and which is

a pressure regulated valve,

- a non-magnetic support frame for supporting the scrubber container and the first and second pressure container and optionally other components of the diving rebreather.

Thus the diving rebreather according to the invention is an electronic closed circuit mixed gas diving rebreather. In the present application, non-magnetic should be understood as generating an exter nal magnetic field of less than 20 nano Tesla, preferably less than 10 nano Tesla, even more preferably less than 5 nano Tesla and most preferably less than 3 nano Tesla.

When a material or a part is referred to as being non-magnetic it should thus be under stood that it does not produce an external magnetic field larger than the values above.

Non-magnetic materials which can be used for the non-magnetic components de- scribed in the present application are titanium alloys, ceramic materials, carbon or fibre-reinforced plastic.

Diluent refers to a gas mix used in diving. It is usually a mix of oxygen and nitrogen (known as nitrox), oxygen and helium (known as heliox), or oxygen, nitrogen and helium (known as trimix). The mix is used as a fill gas to give volume in the breathing loop, thereby reducing the oxygen partial pressure of the gas in the gas loop of the diving rebreather. The exact fraction of the individual gases in the mix depends on the maximum diving depth. The gas in the gas loop is breathable gas. The gas in the gas loop is a mixture of oxy gen and the diluent as described above.

The first valve and piezoelectric actuator can be a single component. The first valve and the piezoelectric actuator can be an ASCO series 630 piezotronic valve. The in- temal parts can comprise piezo ceramics.

Piezoelectric actuators provide actuation without the generation of an external elec tromagnetic field. Actuation is generated based on the piezoelectric effect, where a mechanical stress on a suitable material such as certain ceramics or crystals produces an electrical charge within the material. Typically, the crystals will expand/retract, thereby providing the necessary mechanical movement. For actuation, this process can be reversed. The first valve and/or piezoelectric actuator can have a power consumption of less than 125 milli Watt (mW), preferably 46 mW, even more preferably 32 mW, most preferably 3 mW during hold operation.

The response time of the first valve and/or piezoelectric actuator can be below 800 milli seconds (ms), preferably below 650 ms, even more preferably below 320 ms, most preferably below 130 ms.

Fast response times allow for an exact control of the partial pressure of oxygen in the rebreather.

The fast response times allows for an increased safety, as overpressure in the gas loop can be avoided by swift closing of the first valve.

The person skilled in the art refers to the second valve as an automatic diluent valve. The second valve supplies diluent gas to the gas loop whenever a substantial negative pressure is experienced within the gas loop. Alternatively, the second valve can be operated manually.

The counterlung may be incorporated in the scrubber container.

The counterlung can be placed at different places in the gas loop. For example, the counterlung can be placed before the carbon dioxide scrubber or after the carbon diox ide scrubber.

A first counterlung can be placed before the carbon dioxide scrubber and a second counterlung can be placed after the carbon dioxide scrubber.

The container can for example be a cylinder or an oval canister.

The scrubber container is made of a non-magnetic material such as carbon, titanium alloys or fibre-reinforced plastic. The first and the second pressure containers are preferably pressure gas flasks. The first and second pressure containers can be removable. The first and second pressure containers are made from a non-magnetic material as for example carbon, titanium or fibre-reinforced plastic. The first and the second pressure container typically each in clude an integrated valve. The integrated valves are open/close valves.

The first pressure regulator is typically located directly at the integrated valve of the first pressure container.

The second pressure regulator is typically located directly at the integrated valve of the second pressure container.

The first and second pressure containers typically contain gas with a pressure between 100 to 300 bar. This pressure is reduced to typically 6 to 10 bar in the first and second pressure regulators. To reduce points of failure, it is advantageous to reduce the pres sure in the system as close to the first and second pressure containers as possible.

The first and second pressure regulators are control valves which provide a first stage of pressure regulation. The first stage pressure regulation reduces the high pressure of the first and second pressure container to a constant input working pressure of the first and second valves. The first valve and/or second valve provide a second stage pres sure regulation which precisely adjusts a gas pressure in the gas loop.

The diving rebreather may contain D-rings. The D-rings are used for fastening equip ment and the like. The D-rings can be made of a non-magnetic material such as car bon, titanium or fibre-reinforced plastic.

During use, the diving rebreather is mounted on the diver’s back.

The diving rebreather is adapted for back mounting.

The diving rebreather can comprise a first display for displaying status indications and/or warnings to the diver. The first display may be a hand-mounted display. The diving rebreather can comprise a second display for displaying status indications and/or warnings to the diver. The second display may be a head-mounted display.

The diving rebreather can comprise an overpressure valve.

The diving rebreather can comprise a first manual bypass valve. The first manual by pass valve can be activated manually. The first manual bypass valve injects oxygen gas into the gas loop when activated.

The diving rebreather can comprise a second manual bypass valve. The second manu al bypass valve can be activated manually. The second manual bypass valve injects diluent gas into the gas loop when activated.

The diving rebreather can comprise a bailout demand valve. The bailout demand valve can be used by the diver to access diluent gas directly in case of emergency.

In a further embodiment, the diving rebreather is peculiar in that the piezoelectric ac tuator is a linear actuator.

A linear actuator achieves a simple reliable design of the actuator. It alleviates the need for gears and/or rotary motors which are more error prone and thus less reliable.

In a further embodiment, the diving rebreather is peculiar in that it only consists of components with an external magnetic field strength smaller than 10 nano Tesla, pref erably 5 nano Tesla, more preferably 3 nano Tesla.

The technical effect achieved is a completely non-magnetic rebreather which is not detectable with magnetic sensors and does not activate magnetically activated sea mines.

In a further embodiment, the diving rebreather is peculiar in that the first valve and/or the second valve are normally closed valves. Normally closed valves are valves that revert to a pre-determined position after the actuating force is removed, which pre-determined position is the position in which the valve is closed. They are also referred to as "fail-safe" valves.

Normally closed valves increase the safety of the diving rebreather by preventing the system from overpressure in case of a valve or pressure regulator failure.

In a further embodiment, the diving rebreather is peculiar in that the first valve is ori ented such that a pressure force provided by the oxygen gas on a pressure side of the first valve places the first valve in a closed position in the absence of actuation of the valve.

In a further embodiment, the diving rebreather is peculiar in that the second valve is oriented such that a pressure force provided by the diluent gas on a pressure side of the second valve places the second valve in a closed position in the absence of actua tion of the valve.

The safety of the diving rebreather is increased in case of a failure of the first or sec ond pressure regulator. Overpressure cannot unintentionally open the first and/or sec ond valves. Instead, the valves close when an overpressure occurs. The person skilled in the art also refers to this as the valve being mounted as upstream. This increases the safety of the diver. If overpressure occurring on the pressure side of the first or second valve could open the first or second valve, overpressure would occur in the gas loop of the diving rebreather. The person skilled in the art also refers to this as the valve being mounted as downstream. The overpressure occurring in the gas loop immediately ren ders the diving rebreather unusable for the diver.

However, if the valves are closed instead, when an overpressure occurs, the diver can still use the diving rebreather with the gas volume contained in the gas loop. Thus, the diver has enough time to connect an external gas source to the diving rebreather and bypass the faulty pressure regulator. The gas in the gas loop is filtered by the carbon dioxide scrubber, which additionally increases the time available to the diver. In a further embodiment, the diving rebreather is peculiar in that the diving rebreather further comprises quick couplings for connecting an external oxygen gas and/or dilu ent gas source.

The technical effect achieved is added safety in case of failure of components in the diving rebreather or empty first or second pressure containers. In this case, an external oxygen diluent supply can be connected to supply the diver with breathable gas.

In a further embodiment, the diving rebreather is peculiar in that the diving rebreather comprises three oxygen sensors.

The technical effect achieved here is added safety by redundancy. If sensor readings from the three sensors are within 8% of each other, the average of all three sensors is assumed to be the correct sensor reading. If one of the sensors is off more than 8%, then the average of the remaining two sensors is assumed to be the correct sensor reading. Thus, redundancy over failure of a single sensor is achieved.

In a further embodiment, the diving rebreather is peculiar in that the first and/or sec ond valves are enclosed by a sound-insulating material.

Insulation of the valve allows for a noise reduction of the diving rebreather. Noise reduction is desirable both in recreational use to avoid disturbance of wildlife and in military use to avoid detection by underwater microphones.

In a further embodiment, the diving rebreather is peculiar in that it further comprises non-magnetic counterweights placed on the hose.

The counterweights on the hose counterbalance the buoyancy of the gas in the hose.

A further aspect of the invention is the use of a diving rebreather according to any of the embodiments mentioned above for diving at water depths greater than 10 meters, preferably greater than 30 meters, more preferably greater than 100 meters. Description of the Drawing

The invention is described in the following with reference to the drawing, where

Fig. 1 shows a diagram of a diving rebreather according to the invention.

List of reference numerals

1 diving rebreather

2 gas loop

3 carbon dioxide scrubber

4 scrubber container

5 counterlung

6 hose, for breathing

7 inhale part, hose

8 exhale part, hose

9 gas-transferring member

10 directional valves

11 oxygen sensor

12 microcontroller

13 first pressure container

14 first pressure regulator

15 oxygen cylinder valve

16 power source

17 first valve

18 piezoelectric actuator

19 second pressure container

20 second pressure regulator

21 second valve

23 pressure regulated valve

24 support frame

25 first display

26 second display

27 overpressure valve 28 quick couplings

29 first manual bypass valve

30 second manual bypass valve

31 sound-insulating material

32 non-magnetic counterweights

Detailed Description of the Invention

Fig. 1 shows a schematic drawing of a diving rebreather 1 according to the invention. The diving rebreather is a closed circuit mixed gas rebreather. It supplies the diver with a breathable gas with a well-defined partial pressure of oxygen during diving. The diving rebreather comprises a gas loop 2, which provides a one-directional circu lation of gas which is actuated by the breathing of the diver (not shown). The gas loop 2 comprises a counterlung 5, a scrubber container 4, which contains a carbon dioxide scrubber 3, a gas-transferring member 9 chosen between a mouthpiece or a facemask arranged for transferring the gas to the diver, and at least one hose 6. The hose is con nected with the scrubber container 4, the counterloung 5 and the gas transferring member 9. The hose 6 has an inhale part 7 and an exhale part 8. The carbon dioxide scrubber 3 removes carbon dioxide from the gas.

The counterlung 5 can be incorporated into the scrubber container 4 as additional space for gas in the container.

Two directional valves 10 provide a one-directional circulation of the gas in the loop. The breathing action of the diver circulates the gas in the gas loop. Three oxygen sensors 11 are placed between the carbon dioxide scrubber 3 and the connecting means 9. The oxygen sensors 11 are connected to a microcontroller 12.

The diving rebreather further comprises a first pressure container 13. The first pres sure container 13 contains oxygen gas. The first pressure container is connected to the gas loop 2 via a first pressure regulator. The first pressure container is an oxygen cyl inder or gas flask with an oxygen cylinder valve 15. The first pressure container is made from a non-magnetic material, for example carbon. The microcontroller 12 regulates an oxygen gas supply to the gas loop 2.

The three oxygen sensors 13 measure the oxygen content of the gas in the gas loop 2 in a position between the carbon dioxide scrubber 3 and the gas-transferring member 9.

The diving rebreather comprises a power source 16. The power source powers the microcontroller 12.

The diving rebreather comprises a first valve 17 for regulating the oxygen gas supply to the gas loop 2. The first valve is a non-magnetic on-off valve.

A piezoelectric actuator 18 actuates the first valve. The piezoelectric actuator 18 is non-magnetic. The piezoelectric actuator 18 is a linear actuator.

The diving rebreather further comprises a second pressure container 19. The second pressure container 19 contains a diluent gas. The second pressure container is made from a non-magnetic material. The second pressure container is connected to the gas loop via a second pressure regulator 20.

The diving rebreather comprises a second valve 21 for regulating the diluent gas sup ply to the gas loop. The second valve 21 is non-magnetic. The second valve is a pres sure regulated valve 23. The person skilled in the art refers to the second valve 21 as an automatic diluent valve. The second valve 21 supplies diluent gas to the gas loop whenever a substantial negative pressure is experienced within the gas loop. Alterna tively, the second valve 21 can be operated manually.

The first 14 and second pressure regulators 20 are control valves which provide a first stage of pressure regulation. The first stage pressure regulation reduces the high pres sure of the first 13 and second pressure containers 19 to a constant input working pressure of the first 17 and second valves 21. The first valve 17 and/or second valve 21 provide a second stage pressure regulation which precisely adjusts a gas pressure in the gas loop 2. A non-magnetic support frame 24 for supporting the scrubber container and the first 13 and second pressure containers 19 and optionally other components of the diving rebreather 1.

The diving rebreather 1 only consists of components with an external magnetic field strength smaller than 10 nano Tesla, preferably 5 nano Tesla, more preferably 3 nano Tesla.

The first valve 17 is a normally closed valve. The second valve 21 is a normally closed valve.

The first valve 17 is oriented such that a pressure force provided by the oxygen gas on a pressure side of the first valve places the valve in a closed position in the absence of actuation of the valve.

The second valve 21 is oriented such that a pressure force provided by the diluent gas on a pressure side of the second valve places the valve in a closed position in the ab sence of actuation of the valve.

The diving rebreather comprises a first display 25 for displaying status indications and/or warnings to the diver. The first display may be a hand-mounted display.

The diving rebreather comprises a second display 26 for displaying status indications and/or warnings to the diver. The second display may be a head-mounted display.

The diving rebreather comprises an overpressure valve 27. The overpressure valve can also be activated manually.

The diving rebreather further comprises quick couplings 28 for connecting an external oxygen gas and/or diluent gas source.

The diving rebreather 1 comprises a first manual bypass valve 29. The first manual bypass valve 29 can be activated manually. The first manual bypass valve 29 injects oxygen gas into the gas loop 2 when activated. The diving rebreather can comprise a second manual bypass valve 30. The second manual bypass valve 30 can be activated manually. The second manual bypass valve 30 injects diluent gas into the gas loop 2 when activated. The first and/or second valves are enclosed by a sound-insulating material 31.

The diving rebreather comprises non-magnetic counterweights 32 placed on the hose.

The diving rebreather can be used for diving at water depths greater than 10 meters, preferably greater than 30 meters, more preferably greater than 100 meters.

The counterlung 5 can be placed at different places in the gas loop. For example, the counterlung 5 can be placed before the carbon dioxide scrubber 3 or after the carbon dioxide scrubber 3. Also, a first counterlung can be placed before the carbon dioxide scrubber 3 and a second counterlung can be placed after the carbon dioxide scrubber 3.

Claims

1. Electronic closed circuit mixed gas diving rebreather, which supplies a diver with a gas with a well-defined partial pressure of oxygen during diving, which rebreather comprises

- a gas loop, for one-directional circulation of the gas, and comprising

- one or more counterlungs,

- a scrubber container, which contains a carbon dioxide scrubber,

- a gas-transferring member chosen between a mouthpiece or a facemask ar ranged for transferring the gas to the diver,

- a first pressure container, which contains oxygen gas and which first pressure con- tainer is connected to the gas loop via a first pressure regulator,

- a microcontroller, which regulates an oxygen gas supply to the gas loop,

- a power source for powering the microcontroller,

- a first valve for regulating the oxygen gas supply to the gas loop,

characterised in that the electronic closed circuit mixed gas diving rebreather further comprises, - a piezoelectric actuator, which actuates the first valve, which piezoelectric actuator is non-magnetic,

- that the first valve is a non-magnetic on-off valve,

that the first pressure container is made from a non-magnetic material, and

that the diving rebreather further comprises

- a second valve for regulating the diluent gas supply to the gas loop, and which sec ond valve is non-magnetic, and which is a pressure regulated valve,

2. Diving rebreather according to claim 1, characterised in that the piezoelectric ac tuator is a linear actuator.

3. Diving rebreather according to any of the previous claims, characterised in that it only consists of components with an external magnetic field strength smaller than 10 nano Tesla, preferably 5 nano Tesla, more preferably 3 nano Tesla.

4. Diving rebreather according to any of the previous claims, characterised in that the first valve and/or the second valve are normally closed valves.

5. Diving rebreather according to any of the previous claims, characterised in that the first valve is oriented such that a pressure force provided by the oxygen gas on a pres sure side of the first valve places the valve in a closed position in the absence of actua tion of the valve.

6. Diving rebreather according to any of the previous claims, characterised in that the second valve is oriented such that a pressure force provided by the diluent gas on a pressure side of the second valve places the valve in a closed position in the absence of actuation of the valve.

7. Diving rebreather according to any of the previous claims, characterised in that the diving rebreather further comprises quick couplings for connecting an external oxygen gas and/or diluent gas source.

8. Diving rebreather according to any of the previous claims, characterised in that the diving rebreather comprises three oxygen sensors.

9. Diving rebreather according to any of the previous claims, characterised in that the diving rebreather further comprises non-magnetic counterweights placed on the hose.

10. Use of a diving rebreather according to any of the previous claims for diving at water depths greater than 10 meters, preferably greater than 30 meters, more prefera bly greater than 100 meters.