Closed circuit breathing apparatus

May 28, 1968

L. R. PHILLIPS

3,385,293

CLOSED CIRCUIT BREATHING APPARATUS

Filed June 21, 1965

Sheets-Sheet 1

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Attobme'vs

May 28, 1968

L. R. PHILLIPS

3,385,293

CLOSED CIRCUIT BREATHING APPARATUS

Filed June 21, 1965

Sheets-Sheet 2

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Investor l~&amp;uiis Raymond Phillips

At-to^EVS

United States Patent Office

3,385,293

Patented May 28, 1963

3,385,293

CLOSED CIRCUIT BREATHING APPARATUS Lewis Raymond Phillips, Frimley, Aidershot, England, assignor to Siebe Gorman &amp; Company Limited, Surrey, England, a British company

Filed June 21, 1965, Ser. No. 465,551

Claims priority, application Great Britain, June 27, 1964 26,678/64

Claims. (CI. 128—140)

ABSTRACT OF THE DISCLOSURE

A closed circuit breathing apparatus of the type adapted to be harnessed to the user and having an outer shell in which are located compartments, one of which contains a breathing bag and another contains a receptacle for a chemical charge through which the gas exhaled by the user is passed, via a passage in the shell, for removing the carbon dioxide from the exhaled gas, the gas thus purified being circulated via a third compartment containing a breathing bag to a passage through which the purified gas is inhaled. Means are provided inside the shell, in the form of a heat exchange device, to cool the gas just prior to its being inhaled. This means comprises, at the upper part of the outer shell, a compartment extending horizontally across the shell and charged with ice or other suitable cooling agent capable of being evaporated by the flow of the gas over the exterior of such latter-mentioned compartment. This compartment has in its base openings for the slow escape of the liquid derived from the cooling agent into passages communicating at their ends with a coating of absorbent material forming a jacket for the shell, whereby over the period during which the cooling agent is being evaporated, the shell is substantially completely moistened, thus enabling the moistening to be maintained for all normal conditions of use of the portable breathing aonaratus.

This invention relates to a closed circuit breathing apparatus incorporating carbon dioxide trapping means, e.g. breathing apparatus of the kind known as self-contained oxygen breathing apparatus, in which a chemical charge is contained in a housing usually in the form of a canister, the carbon dioxide being removed from the air exhaled by the user by passing it through the chemical charge, which is gas absorbent.

Closed circuit breathing apparatus of this type comprises a vessel, e.g. the customary cylinder, containing a supply of compressed oxygen, and an expansile reservoir such as a breathing bag of resilient material, or a compartment containing an “inside-out” breathing bag, into which reservoir or compartment the oxygen cylinder communicates via its reducing valve and a tube leading from the outlet of the reducing valve, so that a flow of oxygen passes from the cylinder into said reservoir or compartment, and the mouthpiece or face mask connected to the reservoir or compartment through an inspiratory valve, and through a vent valve to a vessel containing a material capable of absorbing carbon dioxide, which vessel is also connected to the reservoir, the arrangement being such that at least part of the gas exhaled by the user of the apparatus is returned to the reservoir after having passed through the carbon dioxide absorbing material and is there mixed with fresh oxygen. Such exhaled gas contains an appreciable proportion of air or oxygen and can be breathed again after its carbon dioxide content has been removed.

Generally, with the foregoing and similar closed circuit breathing apparatus, exhaled air is purified to remove car45 bon dioxide by means of a chemical filter which may be caustic soda, soda-lime or some such similar substance. The chemical reaction is exothermic, and a significant increase in temperature of the air takes place. The purified air at high temperature is objectionable to breathe, and it is often the practice to include with the apparatus some form of heat exchange in the circuit to reduce this temperature. Passing the air over a container holding sodium phosphate is one example of this practice. In other cases a container accommodating ice or solid carbon dioxide has been employed.

According to the present invention, a closed circuit breathing apparatus is characterised by the provision therewith of a compartment adapted to be charged with a cooling medium such as e.g. ice or water, capable of being evaporated during the use of the breathing apparatus, means being provided to distribute the evaporable cooling medium passing from the source of supply over the exterior of the body shell of the apparatus.

Further, in accordance with the present invention, a closed circuit breathing apparatus comprises in addition to a mouthpiece with inhalation and exhalation valves, a tiered arrangement of three compartments, the uppermost one of which is a container for a charge of the evaporable coolant, over which the air to be breathed passes to the inhalation valve of the mouthpiece, the other two compartments comprising a breathing bag compartment and a compartment containing a charge of carbon dioxide absorbing material, a coating of porous material applied externally to the body shell and means to provide a slow distribution, or drip-feed of the cooling medium in liquid form from the uppermost compartment to said coating.

Desirably, the “slow distribution or drip-feed” is derived from capillary attraction, by means of wick material or capillary tubing connecting the coolant container to said coating.

Desirably, there is an intimate association of the foregoing part of the apparatus containing the carbon dioxide absorbing material, and the part of the apparatus into which the purified air from the absorbing material passes, usually in a circuitous path, before flowing therefrom to the conduit through which the purified air passes to the inhale part of the mouthpiece of the apparatus, this conduit desirably having an intimate association with the source of supply of the cooling medium to obtain an additional heat exchange action before the air reaches the mouthpiece.

Still further, in accordance with the present invention, a closed circuit breathing apparatus includes above a container for a cartridge or charge of the carbon dioxide absorbing material, a container adapted to accommodate a charge of ice, water or other suitable substance capable of being evaporated under the conditions in which the apparatus is to be used, the container for the said cartridge or charge of carbon dioxide absorbing material having an external coating of porous material, and said container for the ice or other cooling medium being provided with restricted outlets through which the cooling medium in liquid form may flow on to the said coating of porous material, whereby such coating will become saturated with the cooling liquid, the said coating being continued externally over the part of the apparatus receiving the purified air from the said absorbing material, whereby the air for inhaling by the user flows over the latter mentioned part of the apparatus and around the container for the cooling medium to the face mask.

An embodiment of the present invention is illustrated •by the accompanying drawings, wherein,

FIGURE 1 is a sectional front elevation view of the apparatus, i.e., the side of the apparatus opposed to the back or chest of the user of the apparatus depending upon

3,385,293

Ci whether the apparatus is carried slung by a suitable harness over the back or supported in front of the user, and, FIGURE 2 is a side elevation view of FIGURE 1 looking in the direction of the arrow of FIGURE 1, and partly broken away at its upper and lower parts to expose the compartment containing the ice or other suitable coolant, and the cartridge of carbon dioxide absorbing material.

Referring to the drawings, the example of apparatus to which the present invention is applied, follows in many respects known practice in which an outer brass or sheet metal causing 1 is divided into a compartment 2 accommodating a breathing bag 3, i.e., an “inside-out” breathing bag, and a compartment 4 accommodating a carriage 5 for a charge of carbon dioxide absorbing material, the body shell having an arched base 6 against which is nested a cylinder 7 containing a charge of compressed oxygen and secured in position by straps 8 with one end thereof carrying the reducing valve 9, by means of which the user of the apparatus may regulate the flow of oxygen to the compartment 2 via a tube 10, this reducing valve desirably functioning to provide a substantially constant oxygen flow at a level which provides an adequate supply of oxygen supplementing the purified air passing into the compartment 2 from the compartment 4 via openings 11 and 12 in the opposed walls of the respective compartments 2 and 3.

Exhaled air passes along a pipe 13 to the inlet end 14 of the cartridge 5, this cartridge being secured in the compartment 4 by a suitable cap 15 provided with the usual sealing means, the casing of the cartridge comprising a cylindrical member of perforated metal, held in substantially concentric spaced relationship in the compartment 4.

It will be seen that the oxygen from the cylinder 7 and the purified air from the compartment 4 passes over the breathing bag 3 and from thence through openings 16 and 17 at opposite ends of a partition 18 separating from the compartment 2 a compartment 19 of elongated cylindrical or other suitable shape open at one end which is extended beyond the shell and threaded to receive a cap 20 which has a small bleed hole 21. This compartment 19 receives a charge of a suitable coolant such as a bar of ice 22, and consequently, due to the influence of the warm mixture of oxygen and air supplied from the cylinder 7 and compartment 4 respectively, a highly efficient heat exchange takes place between the air to be breathed by the user and the compartment 19. This results in a slow melting of the ice block 22, and the evaporable liquid passes from the compartment 19 through any suitable number of restricted outlets 23 registering with holes in a corresponding number of transversely disposed tubes 24 which extend at their ends beyond the front and rear walls of the casing 1 for a short distance, so as to cause the liquid passing therethrough a drip directly on to a coating 25 of absorbent material applied to the exterior of the shell casing, and desirably extending completely over the whole of the body shell comprising the compartments 19, 2 and 4.

The tubes 24 may be capillary tubes or preferably tubes having threaded through them lengths of wick 24α serving to convey the water by capillary action to the absorbent material, the length of wick desirably being spread at their outer ends at as 24b, and secured to the upper parts of the absorbent material 25. Thus, there is an intimate distribution of moisture over the parts of the apparatus which are subjected to heat from the air passing through the exhaling tube 13 and also the air passing from the compartment 4 into the compartment 2.

The compartment 2 and the compartment 4 may have sandwiched between them a layer of heat insulating material 29 to prevent excessive heat being conducted between the two compartments.

It will be seen from the foregoing that air drawn into the inhaling tube 26 is kept to an easy breathing tempera ture so long as the supply of cooling medium 22 is not fully consumed.

It will be appreciated that the porous covering material 25 forms a jacket over the body shell, and it may be of any suitable form such as e.g. one or more layers of textile fabric, cellular sheet material, the cells of which are in communication with each other, and other material which will not deteriorate over use.

The apparatus is enclosed in a suitable cover such as a moulding of fibre glass which will envelop all those parts of the body shell which could be easily damaged during use of the apparatus, this cover, a rear plate of which is indicated by the reference numeral 30 in FIGURE 2, being so arranged as to leave the body shell open to the ambient air between the body shell and the back (or chest) of the user to allow the air to pass freely over the set and to facilitate the evaporative cooling effect of the moistened material 25.

During the passing of the purified air from the cartridge 5, and the passage of this hot humid air through the openings 11 and 12 into the breathing bag compartment 2, the moisture in the air condenses on the inside walls of the body shell, and the temperature of the air drops due to the external ambient air being at a lower temperature.

The usual form of back frame and harness is provided in association with the body shell and/or protective fibre glass cover, and upper and lower tubular members incorporated in this harness are indicated by the reference numerals 27 and 28 respectively.

The face mask, exhale tube and inhale tube are shown diagrammatically in FIGURE 1 by the broken lines 31, 13' and 26', respectively.

The lower part 4a of the compartment 4 and the base of the body shell are radiused to follow the contour of the cartridge 5, and the jacket of absorbent material 25 wraps over this base of the body shell and also over the top of the body shell as well as over the side walls thereof. It is detachably secured in position e.g. by elastic tapes or fasteners. Should it be desired to have a permanent coating of material functioning in the same manner, a coating of floccular material may be sprayed on to a base material applied to the shell.