BACKGOUND OF THE INVENTION AND THE PROBLEM Breathing devices for diving in water may be divided into three main groups, open, closed, and semi-closed systems. In open systems, the inhalation is made from a pressurised bottle, and the exhalation is made directly to the surrounding water. The drawbacks are that unconsumed oxygen gas is breathed directly into the water. During deep-sea diving the air source has to be replaced during the descent and ascent, in order for the diver not to suffer from poisoning or lack of oxygen. The system is relatively noisy; it has a high acoustic profile, and emits air bubbles. Further, it demands a surface organisation, with access to a compressor or pressurised bottles. The advantage is the relative simplicity of the system.

Closed and semi-closed systems involve purification of the exhaled air from carbon dioxide in a container with, for example, calcium hydroxide. The purified gas then continues to a breathing sac, where new oxygen gas is added from a pressurised bottle. It is also possible to add new inert gas from an inert gas-bottle, in order to compensate for any increase in depth. The drawbacks are the complexity and vulnerability of the system for dosage and monitoring, the toxicity of the calcium hydroxide, and the fact that it is a consumable substance that has to be replaced after each dive. Pressurised oxygen entails risk of fire or explosion. This system too, demands an extensive surface organisation, with ability to supply calcium hydroxide, pressurised oxygen, and inert gas. The advantages of a closed system is that the system does not generate any bubbles and has a low noise level, and that there is no need for gas replacement when descending and ascending during deep-sea diving. The advantages

with a semi-closed system are that it produces less bubbles than an open system, and that it has a low noise level. The disadvantage is the difficulty to control the oxygen partial pressure, and the large surface organisation needed in order to provide mixed gas and calcium hydroxide.

THE PURPOSE OF THE INVENTION AND THE SOLUTION TO THE PROBLEM The object of the invention is to provide a breathing apparatus according to the preamble, and which : should be rechargeable, is dependent only on a minimal surface organisation, can remain operative during long periods of time, has a simple construction and is robustly built, lacks sensitive electronic components, utilises exclusively reliable mechanical gauges for monitoring, the function of which are unimportant for the function of the system as such, has a low weight, maintains the oxygen partial pressure relatively constant at low pressures, alternatively maintains PO2 within a narrow interval, has a low noise level and is bubble free at a constant depth, is associated with a very low risk of fire or explosion, and which counteracts an increase in POz during descent/fall.

These objects have been solved through the characteristics indicated in the accompanying claims, DESCRIPTION OF TB DRAWINGS.

In the following, the invention will be described more closely in an embodiment, with reference to the attached drawing, which, highly schematically, shows a breathing apparatus in accordance with the invention.

DESCRIPTION OF AN EMBODIMENT The breathing apparatus according to the invention comprises of a housing 10, in which is arranged an oxygen accumulator 12 in the shape of a container 13, sealed at is upper end, with openings 14 in the bottom of the container, and a heating and/or cooling element arranged in the accumulator. The envelope surface 16 of the container is surrounded, with the exception of its perforated bottom side, by a chamber 18, which is connected, on the one hand to an inlet 20 for incoming exhaled air, and on the other hand to an outlet 22 leading to a carbon dioxide absorber 24, which in turn communicates with a breathing bellows 28, equipped with an outlet 30 for inhalation air.

The container 13 of the oxygen accumulator 12 contains a reversibly oxygen- fixating agent, which may be comprised, e. g., by a metal complex such as, e. g., cobalt- bis-salicylaldehyde-ethylene-diimine (Salcomine), cobalt-bis-3-fluoro-salicylaldehyde- ethylene-diimine (Fluomine), or cobalt-bis-3-ethoxy-salicylaldehyde-ethylene-diimine.

Metal complexes in the form of cobalt phorfyrins may also be used. The use of simple inorganic salts is also contemplated. Said agents possess the feature of fixating oxygen within a certain, lower, temperature interval, and re-releasing the oxygen within a certain, higher, temperature interval. The ambient partial pressure of oxygen also constitutes an important factor thereby, since desorbtion decreases with an increasing pressure. When exhaled gas enters the chamber 18 surrounding the oxygen accumulator 12, the latter is warmed by the exhaled air, and if this heat is not sufficient, heat is supplied by the heating element, so that the oxygen liberated in the container of the accumulator 13 migrates downwards through a particle filter 32, where any chemical dust is separated. The oxygen continues through a further filter 34, consisting e. g. of a silicon gel or a zeolite, preventing water vapour from entering the accumulator.

The outlet of the steam filter 34 communicates with the breathing bellows 28, in which also terminates a conduit 36 from a pressurised bottle 38, which contains a gas.

This gas may be helium or some other gas mixture for diving deeper than 60 meters, or air for shallower diving. The function of the bellows is to act as gas storage between exhalation and inhalation. The inert gas supply may be constituted by two exchangeable five litre-bottles, a helium bottle, or air or some other diveable gas, while the other bottle with compressed air is arranged with a connection nipple 40, so that it may be

easily connected to a manually operable hand or foot pump or the like. In the conduit 36 between the pressurised bottle 38 and the breathing bellows 28 there is arranged a hydrostatic valve 42, and in the breathing bellows there is arranged a pressure relief valve 44.

In the embodiment, the breathing apparatus works as follows: Exhaled air, leaving the mouthpiece of the diver through a hose, is supplied to the chamber 18, and flows around the container 13 of the oxygen accumulator 12 without coming into contact with the oxygen fixating agent existing in the same, which would lead to the liberation of oxygen. The exhaled air passes through to the filter 24, in which the carbon dioxide is filtered. The thus cleaned exhaled air inflates the breathing bellows 28, and at any overpressure the hydrostatic valve 44 is actuated to open the valve 44. During descent, the pressure relief valve compensates the difference in pressure by opening the passage to the pressurised bottle 38. The latter may be refilled in the simplest conceivable manner by pumping with a manual pump. The oxygen released from the accumulator is purified from dust particles in the filters 32 and 34 before the oxygen enters the breathing bellows, where it is mixed with the purified exhaled air.

The oxygen accumulator 12 is charged by being exposed to atmospheric air or oxygen gas from a bottle. The carbon dioxide absorber is reactivated by heat or reduced CO2 pressure.

The invention is not limited to the embodiment described above; rather, a multitude of variations are possible within the scope of the enclosed claims. For example, the breathing apparatus of the invention may be used in connection to smoke diving or other applications, such as the cleaning of tanks, or other types of maintenance work that takes place in a polluted atmosphere. For instance, during smoke diving, where the air pressure is constant, a second embodiment of the invention may be used advantageously, in which the hydrostatic valve and the pressurised container have been removed.

A LISTING OF REFERENCE NUMERALS 10 housing 11 heating or cooling element 12 oxygen accumulator 13 container 14 openings in the bottom of the container 16 envelope surface of the container 18 air chamber 20 inlet 22 outlet 24 carbon dioxide absorber 28 breathing bellows 30 outlet 32 particle filter 34 vapour filter 36 conduit 38 pressurised bottle 40 connection nipple 42 hydrostatic valve 44 pressure relief valve