GB2188553A - Improved breathing apparatus - Google Patents

Description

GB 2 188 553 A SPECIFICATION on immediately; both rapidlyfill the

breathing bag to allowthe wearer a breathable gas in sufficient Improved breathing apparatus quantity. The use of small oxygen bottles as starters is illustrated in French Patent No. 1,349,411 (Fenzy) This invention concerns an improved breathing 70 and GB 828,406 (MSA).

apparatus, more especially it concerns a closed The present invention aims to satisfy several circuit breathing apparatus having dual sources of requirements; to provide sufficient oxygen to oxygen. sustain life for a set duration, and be flexible in Closed circuit apparatus for use in hazardous principleto permit durations for example of atmospheres for escape and rescue purposes are 75 30,60,120 or 180 minutes; to provide a sufficient well known, and may be of a variety of types. It is to volume of oxygen at low breathing volumesjor be noted that such apparatus are not suitable for use example a "rest" situation, at 10 1/min and also at underwater, although they may be briefly high breathing volumesjor example an "escape" submerged. Apparatus intended for rescue work, for situation involving hard physical effort such as example in underground mines, principally 80 climbing inside an oil platform leg, at 100 1/min; to comprise a compressed oxygen bottle and a carbon maintain thetemperature and condition of inspired dioxide absorber, invariably a canister containing oxygen at physiologically acceptable levels; to soda-lime,togetherwith a breathing bag and remove carbon dioxide from exhalations sothatthe breathing tubes, and valvesto ensure one-wayflow concentration of carbon dioxide in the inspired and to prevent overpressurising the system. Oxygen 85 oxygen does not exceed acceptable levels; and to may be supplied into the breathing circuit by a maintain inhalation and exhalation breathing constant flow valve, a demand valve ora resistances within acceptable levels throughout the combination of a constant flow valve and a demand wearing period.

valve. Carbon dioxide is present in the exhalations The present invention provides a breathing from the userof the apparatus, and to prevent 90 apparatus usable as a closed circuit breathing accumulation Of C02 in the breathing gas, the apparatus and comprising a personal gas supply exhalations are passed through soda-lime, which means for inhalation and exhalation, a canister absorbs C02. The chemical reaction during connected to receive the exhalations of a wearer and absorption heats up the purified gas and also containing a charge of a substance capable of produces water vapour, necessitating careful design 95 generating oxygen upon reaction with the carbon and/orcoolers of varioustypes in orderto provide dioxide and moisture in the exhalations, a breathing breathing gas at an acceptable temperature. Open bag connected to the canisterto receive oxygen and circuit apparatus vent exhalations to the purified exhalations and a cylinder of compressed atmosphere, so that no purification is required. oxygen having a dosing valve actuated bythe Compressed oxygen or compressed airopen circuit 100 requirements of thewearer and adapted to feed into breathing apparatus arewidely used alsojor the breathing circuit, suitably between the canister example byfire brigades, butthe venting of and the wearer.

exhalations results in a high usage rate of gas and a In its simplest embodiment, the personal gas relatively short life because of weight limitations if supply means may comprise a single breathing hose the apparatus is to be man portable on land. 105 through which inhalations and exhalations pass, and In certain environments, such as in coal mines and alsothe canister may permittidal (pendulum)flow generally in the chemical and petroleum industries, therethrough. In other embodiments, there are it may be necessaryfor a workerto escapefrom a provided inhalation and exhalation hoses, which are suffocating, toxic or explosive atmosphere, to a safer desirablyfitted with one-way valves to direct gas environment. Avariety of short duration escape 110 flow in the appropriate direction; such valves may be apparatus have been produced underthe name of at either end of the hoses, or may be incorporated in self-rescuers" or "self-rescue sets". In their a mouthpiece fitting or a half- orfull-face mask.

simplest forms they may comprise a canister of The substance capable of generating oxygen is catalystto convert carbon monoxide to non toxic preferably an alkali metal superoxide or mixed carbon dioxide for use in coal mines, or a small, 115 superoxides. It is preferred to use potassium cylinder of compressed air providing a miniature superoxide (K02) which has a greater bound oxygen open circuit set eg 2001 of air at 200 bar pressure will content per unitweight than sodium superoxide. The provide a duration of 8 minutes. As an alternativeto use of such a substance has significant advantages compressed gas escape apparatus, the "chemical in addition to the generation of oxygen in that not oxygen" escape sets have become established, 120 only is carbon dioxide absorbed but also water using an alkali metal oxide which generates oxygen vapour reacts and is removed from the circulating upon exposure to the carbon dioxide and moisture in breathing gas. This is to be contrasted with the usual a user's exhalation. Chemical oxygen sets, however, carbon dioxide absorber, soda lime, which releases sufferfrom the disadvantage that insufficient oxygen watervapour as a reaction product into the breathing is available immediately upon donning the 125 gas. In conventional closed circuit oxygen breathing apparatus, and this has led to the use of "starter apparatus, the circulating breathing gas is saturated candies", which provide a few minutes of oxygen with watervapourwith the resuitthatthe generation by a chemical reaction independent of a temperature of the gas is of great importance since user's exhalations, or bythe provision of a small the physiological tolerance temperature of saturated cylinder containing 5 litres of oxygen which is turned 130air is approximately 530C, whereas for dry air the 2 GB 2 188 553 A 2 tolerance temperature is9VC In a conventional metal breathing bag generally indicated by 1, and apparatus, purified exhalations leaving the soda part of the bag is formed by a metal bulkhead, 2.

lime canister are at temperatures of 50-60'C, so that Mounted on the bulkhead is a canister, 3, containing artificial cooling means or large surface areas for a charge of 2 kg K02 between dust filters (notshown).

cooling are necessary. In the apparatus of the 70 The canister has an inlet, 4, and an outlet, 5, which present invention much higher temperatures can be outlet is connected to the breathing bag. The tolerated bythe use without significant discomfort. bulkhead also carries a compressed oxygen bottle, 6, Nonetheless, the apparatus may incorporate cooling of capacity up to 18001 at 200 bar pressure having a means for gas to be inhaled. Many cooling means reducing valve and pressure gauge, 7, and having a have been suggested and used in the art of 75 line into the breathing bag in which is positioned a conventional breathing apparatus, including heat pressure operated demand valve, shown in outline, exchangers, ice or dry-ice containers, evaporative 8. From the breathing bag, an outlet connection coolers and forced air cooling using an electricfan, piece, 9, having a one-way valve, is attached to an which latter is preferred for use in the present inhalation breathing hose, 10, leading to a invention. 80 mouthpiece, 11, and an exhalation by means of a Itwill be recognised that known breathing valve body, 13, having a ventto-atmosphere valve, apparatus of this type do not have two separate 14, and, between the valve 14 and the inletto the sources of oxygen available to a wearer throughout canister, a further one-wayvalve. A nose-clip, 15, is the nominal duration of the apparatus. The attached by a cord to the mouthpiece. This quantities of oxygen-generating substance and the 85 embodiment of the apparatus is intended to be worn compressed oxygen volume and cylindersize are as a back pack and shoulderstraps and a waist belt selected to provide an oxygen supplyfrom the (not shown) a re to be f itted.

su bsta nce of 1 to 2 f/m i n, ie. suff icient fo r no rma 1 In use, a wearer donning the apparatus inhales, movement orrest, for a desired nominal duration causing, because of the one-wayvalves, a reduction and oxygen is available on demand and as required 90 of pressure within the breathing bag, and actuating from the compressed oxygen cylinder up to the the demand valve to dose fresh oxygen from the maximum requirements of the wearer, eg. to 100-120 cylinder into the breathing bag to satisfythe Ilmin. In one embodiment of the present invention, a immediate requirements of the wearer. Upon the relatively low constantflow of oxygen (eg 1 to 2 wearer exhaling, the exhalations pass through hose Ilmin) is supplied from the cylinder in addition to the 95 12 into the canister 3 where the carbon dioxide and flow on demand. Suitable demand valves and watervapour in the exhalations reactwith the constant flow/demand valves are available from potassium su peroxide to form potassium carbonate commercial sources, and may be actuated by a and potassium hydrogen carbonate and to release reduction of pressure or bythe emptying of the oxygen which fillsthe breathing bag in preparation breathing bag. 100 forthe next inhalation. As back pressure builds up in The breathing bag may be a bladderora the canister and breathing bag, part of each metal-type breathing bag, and may be selected exhalation is vented to the atmosphere through according to the intended use of the apparatus, and valve 14. Should the breathing bag atthe next weight and durability requirements. inhalation, or any inhalation caused by exertion for In a preferred embodiment, a vent-to-atmosphere 105 example, contain insufficient oxygen, the demand valve is incorporated in the breathing circuit valve will operate to dose further oxygen into the between the personal gas supply means and the breathing circuit.

canisterand is positioned and adapted to release Asecond embodiment of the invention is part of the exhaled breath tothe atmosphere before illustrated in Figure 2,towhich reference is now it passesthrough the canister. Accordingly,the life of 110 made. A mouthpiece 21 is connected by a single the oxygen-generating substance is prolonged breathing tube 22to a valve unitcontaining an and/orthe quantity of substance may be reduced, inhalation valve 23 and an exhalation valve 24. An reducing thevolume and weight of the canister. oxygen cylinder35 carries a reducing and demand The apparatus of the invention offers primarily valve block having a pressure gauge 25a, the block improved security and safetyto the wearer 115 being connected by a hose or pipe 26 to the compared to known apparatus, in thatfailure of one inhalation valve 24. Also connected to the hose or oxygen source, forwhatever reason, does not affect pipe is a breathing bag 27 provided with an excess the ability of the other sourceto provide sufficient pressure valve 28. The breathing bag has a further oxygen to sustain life. Furthermore, it has been connection hose or pipe 29to one side of a K02 known forcertain apparatus currently marketed to 120 canister 20. The canister is connected at its other side provide insufficient oxygen in tests on a treadmill so to the exhalation valve by a hose or pipe 31 having an that the wearer would have lost consciousness or excess pressu re valve 32. A close circuit valve 33 has been seriously weakened. The apparatus of the which is effective to open or close the connection invention may also provide considerably extended hose or pipe 29 is f itted therein.

duration which may be necessary while awaiting 125 If the close circu it valve 33 is in the "open" rescue. position, the apparatus operates as a closed circuit The apparatus of the invention is illustrated in the apparatus with supplementary oxygen on demand, accompanying schematic drawings in which Figures in analogous mannerto the apparatus of Figure 1. If, 1 and 2 depicit first and second em bodiments. however, the valve 33 is closed, the apparatus Referring firstlyto Figure 1, the apparatus has a 130 operates as a short duration compressed oxygen 3 GB 2 188 553 A 3 open circuit apparatus. The wearer receives oxygen on demand from the cylinder; the user's exhalations are prevented from passing through the canister, and exhaust to the atmosphere through valve 32. It may be advantageous on occasion to operate in this manner, where the wearer receives only cool dry oxygen from the cylinder.

Claims (7)

1. A breathing apparatus usable as a closed circuit breathing apparatus, comprising a personal gas supply means for inhalation and exhalation, a canister connected to receive the exhalations of a wearer and containing a change of a substance capable of generating oxygen upon reaction with the carbon dioxide and moisture in the exhalations, a breathing bag connected to the canisterto receive oxygen and purified exhalations and a cylinder of compressed oxygen having a dosing valve actuated bythe requirements of the wearer and adapted to feed into the breathing circuit.

2. An apparatus according to claim 1, wherein the cylinder of compressed oxygen is adapted to feed into the breathing circuit between the canister andthewearer.

3. An apparatus according to claim 1 or2, wherein the dosing valve has an associated constant flowvalve.

4. An apparatus according to anyone of the preceding claims, wherein the canister is arranged to permittidal flow therethrough.

5. An apparatus according to anyone of the preceding claims, wherein a single breathing hose forms part of the personal gas supply means.

6. An apparatus according to anyone of the preceding claims, wherein the substance capable of generating oxygen is potassium superoxide.

7. An apparatus according to anyone of the preceding claims, substantially as hereinbefore described.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd,8187, D8991685. Published by The Patent Office, 25 Southampton Buildings, London, WC2A l AY, from which copies maybe obtained.