WO1995031367A1

WO1995031367A1 - Breathing apparatus

Info

Publication number: WO1995031367A1
Application number: PCT/IB1995/000396
Authority: WO
Inventors: Peter Francis Readey
Original assignee: PRISM LIFE SUPPORT SYSTEMS Ltd; Cochran Consulting Inc
Current assignee: PRISM LIFE SUPPORT SYSTEMS Ltd; Cochran Consulting Inc
Priority date: 1994-05-14
Filing date: 1995-05-15
Publication date: 1995-11-23
Anticipated expiration: 1996-11-14
Also published as: AU2416495A; GB9409683D0

Abstract

A breathing apparatus comprising a chamber (12) of variable volume, an absorption means (78) adapted to be able to absorb carbon dioxide from gas passing through the absorption means; and a mouthpiece (14); said chamber, absorption means and mouthpiece being arranged in a closed circuit; a flow control means (32, 34) provided to allow a uni-directional flow of gas from the chamber to the mouthpiece, to the absorption means and thence to the chamber; an exhaust valve (26) provided in the closed circuit, said exhaust valve being adapted to be able to exhaust gas from a closed circuit; a gas supply (18) connected to the closed circuit through a control valve (58).

Description

TITLE

BREATHING APPARATUS

TECHNICAL FIELD

The present invention relates to a breathing apparatus. More particularly, the present invention relates to a self-contained breathing apparatus for use in diving.

BACKGROUND ART

Breathing apparatus are useful in a variety of applications, such as diving and fire fighting.

Breathing apparatus are typically either open circuit, closed circuit, or semi- closed circuit. Open circuit breathing apparatus provide the user with gas that upon exhalation is exhausted to the environment. Consequently, open circuit breathing apparatus tend to place restrictions upon the user. For example, a limit on the time a diver can spend underwater and therefore the depth a diver can attain. Further, the frequent exhaust of gas in a diving environment can disturb creatures the diver is observing.

Closed circuit breathing apparatus provides oxygen to replenish oxygen consumed by the user. There is no exhaust of gas, which makes closed circuit breathing apparatus suitable for military and underwater photography applications. However, closed circuit breathing apparatus tend to be expensive and are not commonly used.

Semi-closed circuit breathing apparatus provide the user with either oxygen, or a mixture of gasses to replenish oxygen consumed by the user. Periodically, some gas is exhausted to the environment. Because the user breathes the gas several times before it is exhausted, semi-closed circuit breathing apparatus provide the user with a longer supply of gas than open circuit breathing apparatus.

Closed circuit and semi-closed circuit breathing apparatus are known as re- breathers. Because the user breathes the same gas several times, carbon dioxide will accumulate in the gas unless it is removed. Typically, the carbon dioxide is removed by a chemical absorbent, such as soda lime. One danger with chemical absorbents such as soda lime is that, upon contact with water, they can produce toxic gasses.

SUMMARY OF THE INVENTION

Accordingly the present invention resides in a breathing apparatus comprising a chamber of variable volume, an absorption means adapted to be able to absorb carbon dioxide from gas passing through the absorption means; and a mouthpiece, said chamber, absorption means and mouthpiece being arranged in a closed circuit; a flow control means provided to allow a uni-directional flow of gas from the chamber to the mouthpiece, to the absorption means and thence to the chamber; an exhaust valve provided in the closed circuit, said exhaust valve being adapted to be able to exhaust gas from a closed circuit; a gas supply connected to the closed circuit through a control valve.

According to a preferred feature of the invention, the absorption means comprises a canister separate from the chamber having an inlet connected to the mouthpiece and an outlet connected to the chamber.

According to a further preferred feature of the invention, the canister accommodates within it, an inner canister supported within the canister to be spaced from the inner walls, said inner canister accommodating an absorption material capable of absorbing carbon dioxide, said inner canister having a second outlet in communication with the outlet of the canister and a second inlet open to the interior of the canister.

According to a still further preferred feature of the invention, the second inlet is associated with a water filtering means capable of a preventing flow of water to the interior of the inner canister.

According to a yet further preferred feature of the invention, the water filtering means is capable of filtering water in a gaseous and a liquid form. According to a preferred feature of the invention, the other end of the canister accommodates a water absorption means.

According to a preferred feature of the invention, the water absorption means comprises a space separated from the interior of the canister by a membrane capable of permitting the flow of water from the interior of the canister into the space and further being capable of preventing the flow of water from the space to the interior of the canister.

According to a further preferred feature of the invention, the water absorption means comprises material capable of absorbing water which is accommodated at the other end of the canister.

According to a preferred feature of the invention, the exhaust valve is capable of opening upon the pressure within the closed circuit attaining a predetermined pressure and then closing on the pressure in the closed circuit attaining a second predetermined pressure, wherein the first predetermined pressure is greater than the second predetermined pressure.

According to a preferred feature of the present invention, the gas supply comprises a reservoir containing a life supporting gas under pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

One embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of the embodiment; and

Figure 2 is a cross-section of the canister shown in Figure 1.

DETAILED DESCRIPTION OF THE EMBODIMENT

The embodiment is directed towards a breathing apparatus for use in diving. The embodiment provides a semi-closed circuit breathing apparatus which can also operate as a closed circuit for short periods of time. An open circuit is also provided as a safety measure. In Figure 1 of the drawings there is shown a breathing apparatus 10 comprising a counterlung 12, a mouthpiece 14, a canister 16 and a gas supply in the form of a high pressure gas cylinder 18.

The counterlung 12 can comprise a rigid chamber having a membrane provided within the chamber. The membrane accommodates variations in the volume of the gas within the counterlung 12 as a user breathes. Alternatively, the counterlung 12 can comprise a flexible chamber, such a bladder. In this form, the bladder expands and deflates to accommodate variations in the volume of gas within the counterlung 12.

The counterlung 12 has a first inlet 20 a second inlet 22 and an outlet 24. An exhaust controlled by an exhaust valve 26 is provided in the counterlung 12. The exhaust valve 26 can exhaust gas from the counterlung 12 when pressure in the counterlung 12 exceeds a predetermined pressure. Preferably, the valve 26 is adjustable to vary the pressure at which the exhaust valve 26 can open. An oxygen sensor 28, such as a galvanic fuel cell, is provided within the counterlung 12. The oxygen sensor 28 is connected to a monitor 30 which provides a signal indication of the partial pressure of oxygen in the counterlung 12.

The mouthpiece 14 includes one way valves 32 and 34 which are arranged such that gas flows through the mouthpiece 14 from the counterlung 12 to the canister 16 as indicated by the arrow A shown in Figure 1. The outlet 24 of the counterlung 12 is connected to the first one way valve 32 by a hose 36 while the second one way valve 34 is connected to an inlet 38 of the canister 16 by a hose 40.

An outlet 42 of the canister 16 is connected to the inlet 22 of the counterlung 12 by a hose 44. The counterlung 12, the mouthpiece 14 and the canister 16 are interconnected to form a closed circuit.

The gas cylinder 18 is connected to a high pressure to low pressure regulator 46 which has a primary low pressure outlet 48, a secondary low pressure outlet 50 and a high pressure outlet 52. The high pressure outlet 52 is connected to a gauge 54 which can be used to monitor the quantity of high pressure gas remaining in the cylinder 18. The secondary low pressure outlet 50 is connected to a secondary mouthpiece 56 which includes a valve (not shown) which is typically closed.

The primary low pressure outlet 48 is connected to a main control valve 58 and a bypass valve 60. The main control valve 58 and the bypass valve 60 are connected to the inlet 20 of the counterlung 12.

The canister 16 is formed of a tubular section 62, and a hemispherical cover 64 sealingly and releasably attached one end of the tubular section 62. The canister 16 further comprises an inner canister 66 having an open end 68 and a closed end 70. The closed end 70 has an aperture 72 formed therein which is in fluid communication with the outlet 42 in the canister 16. In addition the closed end 70 has an inclined face 74 formed in one side thereof adjacent the inlet 38. The inner canister 66 is positioned substantially coaxially with the tubular section 62 such that there is an annular spacing 76 between the side walls of the canister 16 and the inner canister 66.

A carbon dioxide absorbent material 78, such as soda lime, is accommodated within the inner cylinder 66 between end elements which each comprise a filter 80 and a membrane 82. The end elements are supported towards either end of the inner canister 66 to support between themselves the carbon dioxide absorbent material 78. The filters 80 serve to clean the gas passing through them while the membranes 82 prevent the passage of water there through, thereby helping to prevent the carbon dioxide absorbent material 78 from reacting to water vapour in a user's breath. The membranes 82 can be formed of any suitable material, such as the material known as Vyon. Spacers 86 are provided within the inner canister 66 at the closed end 70 to hold the filter 80 and the membrane 82 at that end at a position spaced from the closed end 70.

A water absorption means in the form of a membrane 84 is provided within the hemispherical cover 64 to define a cavity 83. Preferably, the membrane 84 is formed of a substance that allows water to pass through it into the cavity 83 but which will not allow water to pass from the cavity 83 into the remainder of the canister 16. The cavity 83 can be filled with silica gel to absorb water passing through the membrane 84. Alternatively, a drain valve can be provided in the hemispherical cover 64 to allow water within the cavity 83 to be drained to the environment.

A gas flow path which is defined within the canister 16 between the inlet 38 and the outlet 42 comprises the annular spacing 76 between the canister 16 and inner canister 66 and through the inner canister 66 and the filters 80, the membrane 82 and the carbon dioxide absorbent material 78.

The canister 16, the inner canister 66, the filters 80, the membrane 82 and the carbon dioxide absorbent material 78 comprise a carbon dioxide absorption means.

In use, a user will initially have to fill the counterlung 12 to a volume sufficient to enable the user to take a deep breath. The user can fill the counterlung 12 with gas from the cylinder 18 by use of the bypass valve 60. The gas within the cylinder 18 is preferably a pre-mixed gas, still more preferably an oxygen/inert gas mix such as a nitrogen/oxygen mix. It should be appreciated that more than one cylinder 18 may be provided .

To reduce heat loss, the inner canister 66 is preferably formed of stainless steel which is polished on both inner and outer surfaces and the tubular section 62 and the cover 64 of the canister 16 is formed of plastics or other suitable thermally non-conductive material. By controlling heat loss from the inner canister 66, the exothermic properties of the carbon dioxide absorbent material 78 are able to be utilised to warm the gas passing to the counterlung 12.

The membranes 82 help prevent water contacting the carbon dioxide absorbent material 78, reducing the likelihood of caustic soda burn to the user where the carbon dioxide absorbent material 78 which is used comprises soda lime. In addition, the membrane 84 in the cover 64 serves to capture moisture within the canister 16, to help prevent saturation of the membrane 82. As the user inhales through the mouthpiece 14, gas is drawn from the counterlung 12 which thereby decreases in volume. When the user exhales, the exhaled gas passes into the canister 16. The exhaled gas passes through the membrane 82 which prevents water vapour from passing into the carbon dioxide absorbent material 78. The filter 80 cleans the exhaled gas before it passes through the carbon dioxide absorbent material 78. Most of the carbon dioxide is absorbed by the carbon dioxide absorbent material 78, and the remainder of the gas passes through the filter 80 and membrane 82 before returning to the counterlung 12 ready to be inhaled.

To replenish oxygen consumed by the user, the main control valve 58 allows a small quantity of gas to constantly enter the counterlung 12. As a result the pressure within the closed circuit slowly increases due to the additional gas entering from the main control valve 58. When the pressure within the closed circuit exceeds the activation pressure of the exhaust valve 26, the exhaust valve 26 opens and some of the gas in the counterlung is exhausted into the environment until the exhaust valve 26 closes.

Both the main control valve 58 and the exhaust valve 26 are adjustable by the user. The main control valve 58 is adjustable to allow compensation for the activity of the user. If the user is performing strenuous activity more oxygen will be consumed and thus a greater flow of gas from the cylinder 18 will be required. Further, by closing the main control valve 58, the breathing apparatus 10 can be operated in a closed circuit mode. The breathing apparatus 10 can only be used in this manner for a short period of time since the oxygen consumed by the user is not being replenished. However, the ability to operate in closed circuit mode, even for short periods of time, is useful in some situations, such as photography or wherever exhaust bubbles are not wanted.

The exhaust valve 26 is adjustable to compensate for the variations in ambient pressure. As ambient pressure increases, pressure within the closed circuit also increases. It is therefore desirable to adjust the exhaust valve 26 so that gas within the closed circuit will not be exhausted as the ambient pressure increases. Similarly, the exhaust valve 26 is adjusted to assist in decompression by slowly decreasing the pressure in the closed circuit as the user surfaces. Further, the exhaust valve 26 can be used as a secondary buoyancy facility. By adjusting the exhaust valve 26 to a high activation pressure, the exhaust valve 26 allows a high pressure within the closed circuit, thereby providing buoyancy, which is not only useful whilst underwater but can also help a user float on the surface. In the case of the latter, the user would not be breathing using the mouthpiece 14, so the main control valve 58 can be closed to prolong the buoyancy provided by the breathing apparatus 10.

The bypass valve 60 is used to allow the user to add gas into the counterlung 12 manually. This can be useful as the user descends, to compensate for increased ambient pressure.

The gauge 54 allows the user to monitor the quantity of gas remaining in the cylinder 18. Similarly, the monitor 30 allows the user to monitor the partial pressure of oxygen in the closed circuit. If the partial pressure is too low, the user can compensate by use of the bypass valve 60 to add gas from the cylinder 18.

If a small quantity of water enters the canister 16, the user can flush the water by increasing the supply of gas from the cylinder 18 using the bypass valve 60 and forcing the water through the drain valve provided in the canister 16. However, if the user removes the mouthpiece 14 and the canister 16 floods, flushing may not be possible. In this case, the user must abort the dive and return to the surface. The secondary mouthpiece 56 can be used in such a circumstance to supply the user with gas directly from the cylinder 18 whereby the secondary mouthpiece 56 operates in open circuit mode.

As a safety measure, an indicator may be provided to warn the user of a buildup of carbon dioxide. Such an indicator would include a biochemical substance which will change colour in the presence of carbon dioxide, from which the user could infer failure of the carbon dioxide absorption means.

The breathing apparatus of the embodiment provides a semi-closed circuit breathing apparatus which can be operated in closed circuit mode. An open circuit backup system is provided as a safety measure in case of failure of the semi-closed circuit. The breathing apparatus allows the use of existing diving equipment with a rebreather.

It is a characteristic of the apparatus that once in use at a particular depth, the buoyancy of the user does not vary with normal breathing since the volume of the closed circuit and the user's lungs remains substantially constant, with the exception of the regular supply of fresh gas from the gas cylinder. However this is compensated by the exhausting through the exhaust valve.

Modifications and variations of the present invention such as would be apparent to a skilled addressee are deemed within the scope of the present invention.

For example, the breathing apparatus 10 could be fitted with a hydrostatic valve which would automatically add gas from the cylinder 18 to the counterlung 12 as the ambient pressure increases.

Further, the breathing apparatus 10 can be used in a closed circuit configuration by utilising a cylinder 18 storing pure oxygen. However, when used in this configuration, the breathing apparatus 10 is preferably used at a constant depth.

Claims

1. A breathing apparatus comprising a chamber of variable volume, an absorption means adapted to be able to absorb carbon dioxide from gas passing through the absorption means; and a mouthpiece, said chamber, absorption means and mouthpiece being arranged in a closed circuit; a flow control means provided to allow a uni-directional flow of gas from the chamber to the mouthpiece, to the absorption means and thence to the chamber; an exhaust valve provided in the closed circuit, said exhaust valve being adapted to be able to exhaust gas from a closed circuit; a gas supply connected to the closed circuit through a control valve.

2. A breathing apparatus as claimed at claim 1 wherein the absorption means comprises a canister separate from the chamber having an inlet connected to the mouthpiece and an outlet connected to the chamber.

3. A breathing apparatus as claimed at claim 2 wherein the canister accommodates within it, an inner canister supported within the canister to be spaced from the inner walls, said inner canister accommodating an absorption material capable of absorbing carbon dioxide, said inner canister having a second outlet in communication with the outlet of the canister and a second inlet open to the interior of the canister.

4. A breathing apparatus as claimed at claim 3 wherein the second inlet is associated with a water filtering means capable of a preventing flow of water to the interior of the inner canister.

5. A breathing apparatus as claimed at claim 4 wherein the water filtering means is capable of filtering water in a gaseous and a liquid form.

6. A breathing apparatus as claimed at claim 3 or 4 or 5 wherein the canister is of an elongate configuration having a first end wall and a second end wall and at least a side wall interconnecting the end walls, said first end wall accommodating the inlet and outlet, said inner canister being supported from the first end wall and extending substantially coaxially within the canister, said second inlet being spaced from said first and second end wall.

7. A breathing apparatus as claimed at claim 6 wherein the inner canister is of a generally cylindrical configuration whereby the second outlet is provided at one end and said second inlet is provided at the other end.

8. A breathing apparatus as claimed at claim 7 wherein the other end of the inner canister is formed as an open wall, said open wall being closed by said water filtering means which supports the absorption material within the inner canister.

9. A breathing apparatus as claimed at claim 8 wherein the water filtering means includes a gas filter adapted to filter particulate materials from gas flowing into the inner canister.

10. A breathing apparatus as claimed at any one of the preceding claims wherein the other end of the canister accommodates a water absorption means.

11. A breathing apparatus as claimed at claim 10 wherein the water absorption means comprises a space separated from the interior of the canister by a membrane capable of permitting the flow of water from the interior of the canister into the space and further being capable of preventing the flow of water from the space to the interior of the canister.

12. A breathing apparatus as claimed at claim 10 wherein the water absorption means comprises material capable of absorbing water which is accommodated at the other end of the canister.

13. A breathing apparatus as claimed at any one of the preceding claims wherein the exhaust valve is capable of opening upon the pressure within the closed circuit attaining a predetermined pressure and then closing on the pressure in the closed circuit attaining a second predetermined pressure, wherein the first predetermined pressure is greater than the second predetermined pressure.

14. A breathing apparatus as claimed at any one of the preceding claims wherein a secondary mouthpiece is connected to the gas supply through a regulator valve.

15. A breathing apparatus as claimed at any one of the preceding claims wherein the flow control valve is capable of delivering a metered quantity of gas to the chamber and whereby the flow rate through the flow control valve can be selectively varied.

16. A breathing apparatus as claimed at any one of the preceding claims wherein the flow control valve is associated with a bypass valve connected between the gas supply and the chamber.

17. A breathing apparatus as claimed at any one of the preceding claims wherein the canister is formed of a thermally non-conductive material.

18. A breathing apparatus as claimed at any one of the preceding claims wherein the inner canister is adapted to minimise heat loss therefrom.

19. A breathing apparatus as claimed at claim 18 wherein the inner canister is formed of stainless steel where the inner and outer face is polished.

20. A breathing apparatus as claimed at any one of the preceding claims wherein the gas supply comprises a reservoir containing a life supporting gas under pressure.

21. A breathing apparatus as claimed at claimed at claim 20 wherein the gas comprises oxygen.

22. A breathing apparatus as claimed at claim 20 wherein the gas comprises a mixture of oxygen and an inert gas.

23. A breathing apparatus substantially as herein described with reference to the accompanying drawings.