GB2119659A

GB2119659A - Breathing device having irreversible moisture indicator

Info

Publication number: GB2119659A
Application number: GB08309115A
Authority: GB
Inventors: Elmer S Mckee; Ronald E Thompson; William M Lambert
Original assignee: Mine Safety Appliances Co
Current assignee: MSA Safety Inc
Priority date: 1982-04-28
Filing date: 1983-04-05
Publication date: 1983-11-23
Also published as: DE3315070C2; FR2526166B1; DE3315070A1; GB2119659B; FR2526166A1

Abstract

An emergency breathing device comprises an oxygen-emittive moisture-reactive chemical substance contained within a canister (40), a retractable mouthpiece assembly (36), and a breathing bag (38). In use, moisture exhaled by the user of the device reacts with the oxygen- emittive substance to produce oxygen. The device has an indicator which irreversibly and visually indicates whether moisture has at any time infiltrated into the interior of the breathing device to detrimentally affect the oxygen-emittive capacity of the chemical substance. Potassium superoxide is disclosed as both a preferred oxygen-emittive chemical substance and as a preferred moisture-indicator medium. <IMAGE>

Description

SPECIFICATION Breathing device having irreversible moisture indicator This invention relates to breathing devices and more particularly to emergency breathing devices sensitive to moisture and moisture indicator devices therefor.

Emergency breathing devices have been produced by positioning a supply of an oxygenemittive reactive chemical composition within an appropriate dry-sealed enclosure. Upon encountering an unhealthy atmosphere, a user may breath into and out of the sealed enclosure, with his oxygen requirements being provided by the emission of oxygen from the reactive chemical composition contained therein.

Generally, however, the chemical composition has a finite oxygen-emittive capacity which diminishes upon reaction with moisture which enters the enclosure. Thus, a non-sealed enclosure may result in a non-functional emergency breathing device. This necessitates that some provision be made to indicate that the enclosure remains in a moisture-proof condition. Preferably, such a moisture indicator is one which may be visually monitored for quick assurance that the breathing device remains functional.

It is known that particular substances are reactive with moisture and change colour as a result of exposure thereto. U.S. Patents Nos.

2,460,065; 2,460,066; 2,460,068; 2,460,069; 2,460,070; 2,460,071; 2,460,072; 2,460,073; 2,460,074; 2,526,988; and 3,172,731 disclose examples of such substances useful as moisture indicators. For example, cobalt salts are known to be blue when dry and pink when moistened.

However such salts generally react reversibly with the moisture in an atmosphere, e.g. cobalt changes back from pink to blue when dried. This reversibility greatly limits the usefulness of hydrated salts as moisture indicators in emergency breathing devices, for moisture might infiltrate into the breathing device to render it non-functional, after which a dry condition might return a hydrated salt to its "dry colour", thus providing a potentially catastrophically inaccurate indicator of the functionality of the breathing device. Moreover, such salts are not generally responsive enough to the presence of moisture to serve satisfactorily as moisture indicators in an emergency breathing device.For example, such salts may exhibit a lesser affinity to moisture than the oxygen-emittive chemical composition within the enclosure, such that moisture is drawn from the salt by and into the chemical composition to render the chemical composition less effective while simultaneously providing an inaccurate indication thereof. Thus, there exists a need for an emergency breathing device having an improved condition indicator.

According to the present invention, there is provided an emergency breathing device comprising an enclosure having an interior isolated by wall members from an outside atmosphere; a selected material within said enclosure, said selected material having a finite oxygen-emittive capacity which diminishes in response to exposure to moisture; means for permitting a user to breath into and out of said enclosure; and irreversible means for visually indicating the infiltration of moisture within said enclosure.

The present invention also provides a device for visually indicating the presence of moisture in a selected atmosphere, the device comprising a supply of potassium superoxide being reactive positioning said supply of potassium superoxide in communication with only said selected atmosphere in a visually observable position, said supply of potassium superpxode being reactive with moisture in said selected atmosphere to generate a change in colour which is visually observable through said positioning means.

The present invention further provides a method of detecting the intrusion of moisture into an enclosure, comprising positioning a supply of potassium superoxide in a visually observable position within said enclosure, said supply of potassium superoxide being reactive with moisture within said enclosure to undergo a visually distinguishable colour change thereby.

The present invention provides an emergency breathing device which includes a reliable condition indicator for indicating the reactive status of an oxygen emittive material comprising a supply of a moisture-reactive material which is oriented in a visually observable position in the breathing device. The moisture reactive material is very sensitive to the presence of moisture and irreversibly undergoes a visually distinguishable colour change upon exposure thereto. A preferred material includes potassium superoxide, KO2, which irreversibly changes from a yellow colour to white upon reaction with moisture. The irreversible nature of the colour change assures that the moisture indicator reliably indicates the moisture infiltration history of the breathing device.

For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings in which; Figure 1 is a perspective view of an emergency breathing device of the present invention; Figure 2 is a plan view of the emergency breathing device shown in Figure 1, having portions removed for purposes of clarity; Figure 3 is a view taken along line Ill-Ill of Figure 2; Figure 4 is a view taken along line IV--IV of Figure 2, with the front canister member removed to show interior portions; and Figure 5 is a view taken along lines V-V of Figure 2.

Referring to Figures 1 and 2, there is shown an emergency breathing device 10 having a front enclosure member 12, and a rear enclosure member 14 which may be sealingly interconnected by a connection system 16 to form a sealed enclosure therebetween. As best shown in Figure 1, the breathing device 10 may include a plurality of carrying facilities 20 attached to its exterior surfaces to facilitate its convenient use.

Further, the breathing device 10 may include a protective bumper assembly 22 (not shown in Fig.

2) surrounding the connection system 16 to protect and maintain the integrity of the sealing interconnection between front enclosure member 12 and rear enclosure member 14.

With reference also to Figure 3, and although not limiting to the invention, connection system 16 may include an elongated gasket member 24 which is positioned between oppositely arcuate facing edges 26 and 28 of front enclosure member 12 and rear enclosure member 14, respectively. The gasket member 24 is sealingly biased in position therebetween by an elongated retaining band 30 which is C-shaped in cross section and an interwoven retaining strand 32 (not shown in Fig. 3) which surrounds the retaining band 30 and the gasket member 24. A pair of adjacent opening rings 34 are conveniently attached to the retaining band 30 to permit the breathing device 10 to be opened when its use is required.

In this regard and with reference also to Figure 4, there is contained within the breathing device 10 a retractable mouthpiece assembly 36, a breathing bag 38, an internal canister 40, and a valve member 42 which controls the communication therebetween. Within the internal canister 40 there is contained a supply of a selected substance which, upon contact with the moisture in the exhalation of a user, emits sufficient oxygen to sustain human life. In operation, a user exhales into the mouthpiece assembly 35, the exhalation being routed by valve member 42 directly into the internal canister 40, where oxygen is generated which is accumulated within breathing bag 38. Upon inhalation, valve member 42 closes and oxygen is withdrawn by the user directly from breathing bag 38.

In a preferred embodiment of the invention, the selected substance within internal canister 40 comprises potassium superoxide, KO2, which upon exposure to moisture reacts to form potassium hydroxide, KOH, via the following reaction: 4KO2+2H204KOH +302 Of course, due to the finite supply of oxygen available from a given quantity of the selected oxygen-emittive substance, e.g. potassium superoxide, it is very important to seal the interior of the breathing device 10 from moisture intrusion which would diminish or eliminate the functionality thereof in advance of its time for emergency use. Additionally, it is important to provide a convenient condition indicator by which a user may determine at a glance whether a particular breathing device 10 remains functional.

In this regard, and with reference to Figures 1, 2 and 5, an irreversible moisture indicator 44 is provided adjacent the exterior surface of the front canister 1 2. As best shown in Figure 5, the moisture indicator 44 preferably includes a backing plate 46, a receptacle member 48, a filter plate 50 and window member 52 which sealingly interconnect through a gasket 54 and a washer 56 to provide a retaining compartment 58 and a diffusion compartment 60. A quantity of a moisture-indicating substance is positioned within the retaining compartment 58, where it is in communication with the interior of the breathing device 10 through filter plate 50 and backing plate 46 while being isolated from the exterior of the breathing device 10.The window member 52 permits the condition of the moisture indicating substance to be viewed conveniently from outside the breathing device 10, such that an outside observer may readily determine whether moisture has at any time infiltrated into the interior of the breathing device.

As previously mentioned, the moisture indicating substance is preferably one which reacts irreversibly with moisture, and ideally is highly sensitive to even slight amounts of moisture, because of the highly reactive nature of the potassium superoxide as an oxygen-emittive source material. U.S. Patent No. 3,893,172 discloses an irreversible humidity indicator which may be utilized within the retaining compartment 58, including dye particles distributed over the surface of a deliquescent neutral-coloured salt which is disposed on a substrate. Upon exposure to moisture, the dye bleeds into the salt to impart colour thereto which remains after drying.

More preferably, however, a relatively small quantity of potassium superoxide is positioned within the retaining compartment 58, which potassium superoxide has been determined to undergo a visually distinguishable colour change from yellow to white as it reacts with even small quantities of moisture. The potassium superoxide used as a moisture indicator may be in a powdered form, a granular form, or most preferably, may be pressed into convenient pellet form by the application of elevated pressures, e.g.

4000 to 8000 pounds per square inch (2.8 x 107 to 5.6 x 107 N/m2). The potassium superoxide moisture indicator changes from yellow to white upon exposure to moisture, and no known conditions will cause it to revert back to its original yellow colour, thus providing a reliable moisture infiltration indicator which acc.urately identifies the moisture-infiltration history within the breathing device 1 0.

The responsiveness of the moisture indicator may be conveniently varied and controlled by altering the moisture-permeability of the backing plate 46 through which it communicates with the interior of the breathing device 10. For example, the backing plate 46 may be provided with an orifice or orifices therethrough of selected sizes, e.g. 0.030 inch to 0.125 inch (0.76 mm to 3.17 mm) to control the amount of relative moisture that the moisture indicator senses within the diffusion compartment 60 in accordance with Fick's law. Alternatively, the backing plate 46 may be formed of a semi-permeable membrane having a selected permeability to the passage of moisture therethrough.

Claims

1. An emergency breathing device comprising an enclosure having an interior isolated by wall members from an outside atmosphere; a selected material within said enclosure, said selected material having a finite oxygen-emittive capacity which diminishes in response to exposure to moisture; means for permitting a user to breath into and out of said enclosure; and irreversible means for visually indicating the infiltration of moisture within said enclosure.

2. A breathing device is claimed in claim 1, wherein said irreversible visual indicating means comprises an indicator sample of potassium superoxide in communication only with the interior of said enclosure but visually observable from without said enclosure, said indicator sample of potassium superoxide being reactively responsive to the presence of moisture within said enclosure to generate a colour change which is visually observable from without said enclosure,

3. A breathing device as claimed in claim 1 or 2, wherein said selected material comprises a primary quantity of potassium superoxide.

4. A breathing device as claimed in claim 3, further comprising means for controliing the relative reactivities of said indicator sample of potassium superoxide and said primary quantity of potassium superoxide to moisture within said enclosure such that a predetermined colour change in said indicator sample indicates a predetermined diminution in the oxygen-emittive capacity of said primary quantity.

5. An emergency breathing device substantially as hereinbefore described with reference to, and as shown in, the drawings.

6. A device for visually indicating the presence of moisture in a selected atmosphere, the device comprising a supply of potassium superoxide, and means for positioning said supply of potassium superoxide in communication with only said selected atmosphere in a visually observable position, said supply of potassium superoxide being reactive with moisture in said selected atmosphere to generate a change in colour which is visually observable through said positioning means.

7. A device as claimed in claim 6, wherein said selected atmosphere comprises the interior atmosphere of a compartment from which moisture is to be excluded.

8. A device as claimed in claim 7, wherein said compartment contains a material which reacts with moisture in a naturally irreversible chemical reaction.

9. A device for visually indicating the presence of moisture in a selected atmosphere, substantially as hereinbefore described with reference to, and as shown in, the drawings.

10. A method of detecting the intrusion of moisture into an enclosure, comprising positioning a supply of potassium superoxide in a visually observable position within said enclosure, said supply of potassium superoxide being reactive with moisture within said enclosure to undergo a visually distinguishable colour change thereby.

11. A method according to claim 10, substantially as hereinbefore described.