GB2201096A

GB2201096A - Emergency escape breathing apparatus

Info

Publication number: GB2201096A
Application number: GB08703383A
Authority: GB
Inventors: Stephen Jon Brewer; Edwin John Swatton; James Alexand Hammerton-Fraser
Original assignee: Sabre Safety Ltd
Current assignee: Sabre Safety Ltd
Priority date: 1987-02-13
Filing date: 1987-02-13
Publication date: 1988-08-24
Anticipated expiration: 2007-02-13
Also published as: GB8703383D0; GB2201096B

Abstract

In emergency escape breathing apparatus oxygen is fed from a cylinder 7 in a breathing bag 6 to a flexible hood 1 through an inhalation channel which includes an inhalation valve 12 and a pressure responsive valve 9. The pressure responsive valve 12 is maintained in the open condition by a pressure, which may be either a negative or a positive pressure, generated by the flow of oxygen from the cylinder 7 into the breathing bag 6. When oxygen flow from the cylinder 7 ceases, the pressure responsive valve 9 closes to a condition in which only a restricted gas flow through the inhalation valve 12 is permitted, and the resultant increased inhale resistance warns the wearer of the hood 1 that the oxygen supply is exhausted and that the hood 1 should be removed. <IMAGE>

Description

EMERGENCY ESCAPE BREATHING APPARATUS This invention relates to emergency escape breathing apparatus.

It isknown to provide emergency escape breathing apparatus comprising a flexible hood, at least part of which is transparent for affording vision to the wearer, and a breathing set supplying a breathable gas which may be air or oxygen or oxygen-enriched air into the interior of the hood at a predetermined constant rate of flow for a minimum predetermined duration dependent on the size of the gas cylinder. The hood is of a size which can be worn over the head of a wearer of any age or hair style without any adjustment and irrespective of whether the wearer is bearded or wears spectacles.

This known emergency escape breathing apparatus is designed for use in escaping from a location where there may be a toxic or otherwise irrespirable atmosphere, for example a room or corridor which is filled with smoke as a result of a fire. The user simply starts the flow of breathable gas to the hood, pulls the hood over his head, and proceeds through the irrespirable atmosphere to a place of safety.

It has further been proposed that the hood of such an emergency escape breathing apparatus may incorporate an inner mask, i.e. a half mask, with suitable valves to control the build-up of carbon dioxide within the hood. It has also been proposed that a chemical carbon dioxide absorbent may be included if required, and the present Applicants' copending Patent Application No. 86.09389 describes emergency escape breathing apparatus in which the exhaled gas is directed from the half mask through a carbon dioxide filter while inhalation gas enters the half mask through a conventional inhalation valve.

Such emergency escape breathing apparatus is suitable in particular for protecting passengers and crew of an aircraft during a fire. In such apparatus, after scrubbing by the carbondioxide filter, the oxygen content of the exhaled gas is topped up by a supply from an oxygen source, for example a cylinder filled with oxygen under pressure.

With emergency escape breathing apparatus of the type described it is important that there is an adequate supply of oxygen available for the full duration of use. If the hood is put on without the oxygen supply being released, or if the oxygen supply is used up while the hood is still being worn, the oxygen concentration of the gas in the hood will fall. This gives no warning to the wearer who will be quite unaware of the fact that his oxygen concentration is becoming inadequate for supporting life. When the oxygen content has dropped sufficiently, the wearer merely passes out, and unless the oxygen concentration of the gas being breathed is increased by, for example, removing the hood, death will ultimately follow.

This differs from the effect which is encountered when the carbon dioxide absorbent material is used up whilst there is still an adequate oxygen supply in the hood.

At that point the quantity of carbon dioxide in the hood starts to rise leading to discomfort and hyperventilation which ultimately forces the wearer to alleviate the discomfort by removing the hood.

It is an object of the present invention to provide emergency escape breathing apparatus of the type described in which the wearer of the hood is warned of the lack of oxygen supply arising either from a failure to initiate the source of the topping up oxygen or from exhaustion of the source of the topping up oxygen.

In accordance with the present invention there isprovided emergency escape breathing apparatus comprising a flexible hood, at least part of which is transparent, for enveloping the head of a wearer, a half mask positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, a source of breathable gas for maintaining a reservoir of-breathable gas in or adjacent to the interior of the hood, and inhalation means interconnecting the reservoir of breathable gas and the interior of the half mask, the said inhalation means comprising an inhalation valve openable in response to inhalation by the wearer and a pressure responsive valve which is openable in response to a flow of breathable gas from the said source to permit unhindered inhalation through the inhalation means and which its closed in the absence of the flow of breathable gas from the said source to provide increased inhale resistance by restricting the flow of gas through the - inhalation valve.

The pressure responsive valve is so designed that it restricts the flow of breathable gas through the inhalation valve rather than cutting off the flow of breathable gas through the inhalation valve. In consequence the wearer experiences increased inhale resistance when the pressure responsive valve does not open, and the consequential need to exercise greater effort in breathing serves as a warning of a shortage of oxygen.

In emergency escape breathing apparatus according to the present invention the reservoir of breathable gas may be provided in the interior of the hood outside the half mask.

Alternatively, however, there may be further provided a breathing bag for providing the reservoir of breathable gas. This breathing bag may be located outside the hood but, preferably, it is located within the interior of the hood so that the breathing bag is protected by the flexible material of the hood. In the preferred embodiments of the present invention which will be described the breathing bag is located within the interior of the hood and provides a reservoir of breathable gas which is separate from the remainder of the interior of the hood outside the half mask.

More particularly in accordance with the present invention there is provided emergency escape breathing apparatus comprising a flexible hood, at -least part of which is transparent, for enveloping the head of a wearer, a half mask positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, the interior of the half mask being isolated from the remainder of the interior of the hood, a breathing bag connected to a source of oxygen or oxygen-enriched -air for providing a reservoir of breathable gas in a space separate from the interior of the hood, the breathing bag being located within the flexible'hood, and means interconnecting the breathing bag and the half mask for supplying breathable gas from the reservoir to the half mask through an inhalation channel when the wearer of the hood inhales and for passing exhaled gases from the half mask to the breathing bag through an exhalation channel which is separate from the inhalation channel when the wearer exhales, the flow of gas through the inhalation channel being controlled by an inhalation valve and a pressure responsive valve which is maintained in an open position by flow of gas from the said source to permit unhindered inhalation through the inhalation valve and which is closed to provide increased inhale resistance by restricting the flow of gas through the inhalation valve in the absence of gas flow from the said source, and the exhalation channel including a carbon dioxide absorbent filter and an exhale valve.

Advantageously the exhalation channel is formed as an annulus surrounding the inhalation channel.

Preferably the said source is an oxygen cylinder.

The oxygen cylinder or other source may be located externally of the hoodbutpreferably is located within the hood and, most advantageously, is located within the breathing bag within the hood.

The pressure responsive valve which is used in accordance with the present invention conveniently includes a rolling diaphragm which is movable in response to a pressure differential caused by the flow of gas from the said source. The movement of the pressure responsive valve may be in response to either a reduction of pressure caused by the flow of gas from the oxygen cylinder or other gas source through a venturi tube or other fine nozzle, or an increased pressure derived from the flow of gas from the oxygen cylinder or other source.

Advantageously, the flexible hood comprises a flexible flame resistant composite with a rigid visor of transparent material mounted therein. In the embodiments bf the invention which will be described the half mask is mounted to the rigid visor. When desired as, for example, in the case of aircraft cabin crew Mho need to communicate with passengers, a speech diaphragm may be mounted in either the flexible hood or the rigid visor. Desirably the flexible hood also includes a relief valve to allow a pressure build-up in the hood to be relieved, for example in case of a cabin depressurization at altitude.

rC Also a neck seal is provided on the interior of the hood for inhibiting ingress of gas into the hood when the hood is enveloping the head of the wearer.

-The present invention will be further understood from the following detailed description of preferred embodiments thereof which is made by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic representation of emergency escape breathing apparatus in accordance with the invention, Figure 2 is an enlarged cross-sectional view of a canister assembly which constitutes the means interconnecting the breathing bag and the half mask in the apparatus of Figure 1, Figures 3A and 3B show diagrammatically the initiation of gas flow and the creation of a negative differential pressure to operate the pressure responsive valve of the canister assembly of Figure 2, Figure 4 is a cross-sectional view of an.alternative inhalation means to the inhalation means of the canister assembly illustrated in Figure 2, Figure 5 is an enlarged view in part cross-section of a portion of a gas cylinder including means for creating an increased pressure differential for actuation of the pressure responsive valve of Figure 4, Figure 6 is a cross-sectional view, taken on the line VI-VI of Figure 5, of the wall of the gas cylinder and the structure integral therewith and indicating diagrammatically the outlet from the gas cylinder and Figure 7 is a schematic plan view of the means for creating an increased pressure differential taken in the direction of the arrow VII of Figure 5.

In the drawings the same or similar parts are designated by like reference numerals.

Referring to Figure 1 there is shown a flexible hood 1 of a commercially available flame resistant composite formed of a suitable plastics material laminated to a woven base.

A visor 2 of a rigid transparent plastics material, for example perspex or polycarbonate, constitutes a wrap around window heat welded to the flexible hood 1. A speech diaphragm 3 is mounted in the visor 2 enabling the wearer of the hood 1 to communicate readily through the hood, and a flexible half mask 4, for example a rubber half mask, is mounted to the interior of the visor 2. A canister assembly 5, which will be described in more detail with reference to Figure 2, provides an inhalation channel and an exhalation channel interconnecting the interior of the half mask with the interior of a breathing bag 6 located within a lower front part of the flexible hood 1. An oxygen cylinder 7 is located within the breathing bag 6 so that it may discharge oxygen directly into the breathing bag 6.A pressure sensitive line 8 connected adjacent to the flow of the oxygen gas from the cylinder 7 into the breathing bag 6 communicates a change in pressure, in this case a pressure reduction, to a pressure responsive valve 9 of the canister assembly 5, as will b & described in more detail below.

In use, when the half mask 4 engages the face of the wearer of the hood, the interior of the half mask 4 and the breathing bag 6 are entirely separate from the remainder of the interior of the hood 1. A pressure of the order of 50 to 120 mms water gauge above ambient or atmospheric pressure is present in the breathing bag 6.

The gases which are inhaled and exhaled by the wearer of the hood 1 are thus isolated from the gases in the remainder of the interior of the hood 1.

The flexible hood 1 further includes a flexible polurethane neck seal 10 and a relief valve 11 at the rear of the hood for emitting gas when an undesired excess pressure builds up within the hood 1.

Turning now to Figure 2, there is shown a view, partly in cross-section, of the canister assembly 5 which constitutes means interconnecting the breathing bag 6 and the half mask 4, and which includes an inhalation means consisting of a conventional or standard inhalation valve 12 such as- a rubber flap valve, and the pressure responsive valve 9. The inhalation valve 12 and the pressure responsive valve 9 are mounted on opposite sides of a member 13 which provides first and second valve seats 14 and 15 for the inhalation valve 12 and the pressure responsive valve 9 respectively.

In the embodiment of canister assembly 5 illustrated in Figure 2 the first valve seat 14 is a conventional smooth valve seat against which the flaps of the inhalation valve form a seal during exhalation by the wearer of the hood 1. However, the valve seat 15 is castellated or has a wavy profile so that the pressure responsive valve 9 cannot be fully shut off. The castellations or wavy surface of the valve seat 15 are such as to permit a much lower flow of gas past the valve seat 15 when the pressure sensitive valve 9 is closed, than flows through the inhalation valve 12 when the pressure responsive valve 9 is open.

The pressure -responsive valve 9 includes a rolling diaphragm 16, that is to say a diaphragm formed of a flexible material, the part of the diaphragm which engages the valve seat 15 being held rigid by a circular metal disk. A spring 17 maintains the rolling diaphragm 16 in contact with the castellated or wavy valve seat 15 keeping the pressure responsive valve 9 in its normally closed condition.

The pressure responsive valve 9 and the inhalation valve 12 are both mounted in a central inhalation channel 18 passing through the canister assembly 5. Around this central inhalation channel is an annular exhalation channel in which there is located an annular carbon dioxide absorbent filter.l9 of, for example, soda lime, and a conventional exhalation valve 20.

In Figure 3A there -is shown a portion of a side wall 21 of the oxygen cylinder 7. A capillary outlet 22 through this side wall 21 is normally sealed by a firing pin 24.

An actuating member. 25, for example of steel braiding, is secured in an aperture through an upper part of the firing pin 24.

When the emergency escape breathing apparatus of Figures 1 to 3 is to be used, the actuating member 25 is pulled smartly in the direction of the arrow 26 of Figure 3A causing the firing pin 24 to break away from the side wall 21 of the oxygen cylinder and permit flow of oxygen under pressure through the capillary outlet 22 and into the breathing bag 6 as shown by the arrow 27 of Figure 3B.

Oxygen therefore flows speedily past an aperture 28 in an immediately adjacent side wall 29 thereby creating a negative or suction pressure in the aperture 28 and in the pressure sensitive line 8 which is connected to the aperture 28. This negative or suction pressure is conveyed by the pressure sensitive line 8 to-the interior of the pressure responsive valve. 9 causing the rolling diaphragm 16 to be withdrawn from the second valve seat 15 against the action of compression spring 17 to a position such as that shown in dashed lines at 16' in Figure 2. The pressure responsive valve 9 is thus maintained continuously open while oxygen gas flows from the cylinder 7. Normal inhalation through the inhalation valve 12 is thus permitted all the time that oxygen is being provided by the cylinder 7.

However, when oxygen flow from the cylinder 7 ceases, there is no longer any negative or suction pressure in line 8, spring 17 returns the rolling diaphragm 16 into contact with the second valve seat 15 and the pressure responsive valve 9 is closed. In this closed condition of valve 9 the flow of gas through the inhalation channel 18 is restricted, with the result that the wearer of the hood 1 experiences an increased inhale resistance when trying to breath after flow of oxygen from the cylinder 7 has ceased. This increased inhale resistance provides a warning to the wearer of the hood 1 that the hood 1 should be removed as soon as it is safe to do so.

The - emergency escape breathing apparatus described therefore incudes an anti-anoxia device giving warning that the supply of oxygen or other breathable gas has been used up.

An alternative embodiment of the invention in which the pressure responsive valve 9 is maintained in the open position by a positive increased pressure rather than a negative or suction pressure will be described with reference to Figures 4, 5A and 5B.

Figure 4 of the accompanying drawings shows the central part of a canister assembly essentially similar to the canister. assembly 5 of Figure 2 in that there is a central inhalation channel 18 surrounded by an exhalation channel. A carbon dioxide absorbent filter 19 is positioned in the exhalation channel with an exhale valve 20 at the downstream end of the carbon dioxide absorbent filter 19.

In the inhalation channel 18 there is an inhalation valve 12, which is a conventional rubber flap valve, engaging the first valve seat 14 on the member 13. In this case, however, a second valve seat 31 on the member 13 has a continuous smooth profile which is engaged by a smooth-surfaced valve member 32 of a pressure responsive valve 30. An aperture 33 through the valve member 32 ensures that the pressure responsive valve 30 of this embodiment is never fully shut, and the flow of gas through the pressure responsive valve 30 is very much lower than the flow when the valve 30- is open, or the flow through the inhalation valve 12 on its own.

The valve member 32 of the pressure responsive valve 30 is linked by a central rod 34 to a rolling diaphragm 35 forming part of a sealed chamber 36 to the interior of which the pressure sensitive line 8 is connected. Rod 34 passes through a wall 37 of the sealed chamber 36 and a spring 38 acting between the wall 37 and the valve member 32 maintains the valve member 32 in contact with the valve seat 31 in the closed condition of the pressure responsive valve 30.

Referring to Figures 5 to 7, the portion of the cylinder 7 containing the capillary outlet 22 has a curved flange portion 40 spaced from the cylinder side wall 21 by an amount sufficient to accommodate the firing pin 24.

Flange 40 is connected to the cylinder by a wall 41 having an aperture 44 through which the actuating member 25 passes, as shown in Figures 5 and 7.

There is formed in the flange 40 immediately opposite to the capillary outlet 22 from the cylinder 7, a cupshaped recess 42 which gathers oxygen or other gases flowing from the cylinder 7 through the capillary outlet 22 in the cylinder side wall 21. The recess 42 leads to a horizontal opening 43 (Figures 6 and 7) in the edge of the flange 40, and the pressure sensitive line 8 is connected to the opening 43.

When the firing pin 24 is pulled to the left, as seen in Figure 5, by-actuating member 25, which may be a direct manual action or may be in consequence either of the removal of the hood from its package or holder or of the donning of the hood, the firing pin 24 fractures, thereby exposing the capillary outlet 22 through which. gas flows under pressure. Some of this gas flows into the recess 42 creating an increased pressure in the opening 43, pressure sensitive line 8 and the sealed chamber 36,thereby causing the rolling diaphragm. 35 to move to the left as seen in Figure 4 and moving the valve member 32 of valve seat 31 to permit unhindered flow of gas through the inhalation valve 12 when the wearer of the hood inhales through the inner mask.Rolling diaphragm 35 will be maintained in the position displaced to the left from the position shown in Figure 4 for as long as gas flows out of the cylinder through capillary outlet 22. When this flow ceases, the pressure in sealed chamber 36 will drop and spring 38 will return the valve member 32 into engagement with valve seat 31. Further flow through the inhalation channel 18 as a result of inhalation by the wearer of the hood 1 will be restricted by the size of the aperture 33 so that the wearer of the hood 1 will experience increased inhale resistance and will have warning that the hood should be removed immediately or as soon as it is safe to do so.

By the invention described herein there is provided emergency escape breathing apparatus which includes an anti-anoxia device giving warning of the expiry of the oxygen topping-up gas flow in advance of the exhaustion of the carbon dioxide absorbent filter.

In each of the described embodiments of the invention the gas flow through the pressure responsive valve 9 or 30 and hence through the inhalation channel 18 is restricted rather than terminated when the supply of topping-up gas is exhausted. Any design of the pressure responsive valve to permit this restricted gas flow may be employed in any embodiment in accordance with the present invention.

Claims

CLAIMS:

1. Emergency escape breathing apparatus comprising a flexible hood, at least part of which is transparent, for enveloping the head of awBrer, a half mask positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, a source of breathable gas for maintaining a reservoir of breathable gas in or adjacent to the interior of the hood, and inhalation means interconnecting the reservoir of breathable gas and the -interior-of the half mask, the said inhalation means comprising an inhalation valve openable in response to inhalation by the wearer and a pressure responsive valve which is openable in response to a flow of breathable gas from the said source to permit unhindered inhalation through the inhalation means and which is closed in the absence of the flow of breathable gas from the said source to provide increased inhale resistance by restricting the flow of gas through the inhalation valve.

2. Emergency escape breathing apparatus according to Claim 1, wherein the reservoir of breathable gas is provided in the interior of the hood outside the half mask.

3. Emergency escape breathing apparatus according to Claim 1, in which there is further provided a breathing bag for providing the reservoir of breathable gas.

4. Emergency escape breathing apparatus according to Claim 3, wherein the breathing bag is located within the interior of the hood.

5. Emergency escape breathing apparatus comprising a flexible hood, at least part of which is transparent, for enveloping the head of a wearer, a half mask positioned within the hood for engaging the face of the wearer of the hood around the nose and mouth, the interior of the half mask being isolated from the remainder of the interior of the hood, a breathing bag connected to a source of oxygen or oxygen-enriched air for providing a reservoir of breathable gas in-a space separate from the interior of the hood, the breathing bag being located within the flexible hood, and means interconnecting the breathing bag and the half mask for supplying breathable gas from the reservoir to the half mask through an inhalation channel when the wearer of the hood inhales and for passing exhaled gases from the half mask to the breathing bag through an exhalation channel which is separate from the inhalation channel when the wearer exhales, the flow of gas through the inhalation channel being controlled by an inhalation valve and a pressure responsive valve which is maintained in an open position by flow of gas from the said source to permit unhindered inhalation through the inhalation valve and which is closed to provided increased inhale reistance by restricting the flow of gas through the inhalation valve in the absence of gas flow from the said source, and-the exhalation channel including a carbon dioxide absorbent filter and an exhale valve.

6. Emergency escape breathing apparatus according to Claim 5, wherein the exhalation channel is formed as an annulus surrounding the inhalation channel.

7. Emergency escape breathing apparatus according to any one of Claims3 to 6 wherein the said source is an oxygen cylinder located within the breathing bag.

8. Emergency escape breathing apparatus according to any one of the preceding claims wherein the pressure responsive valve includes a rolling diaphragm movable in response to a pressure differential caused by the flow of gas from the said source.

9. Emergency escape breathing apparatus according to any one of the preceding claims, wherein the pressure responsive valve is openable in response to a reduction of pressure caused by the flow of gas from the said source through a venturi tube.

10. Emergency escape breathing apparatus according to any one of Claims 1 to 8, wherein the pressure responsive valve is openable in response to an increased pressure derived from the flow of gas from the said source.

11. Emergency escape breathing apparatus according to any one of the preceding claims, wherein the flexible hood comprises a flexible flame resistant composite having a rigid visor of transparent material mounted therein.

12. Emergency escape breathing apparatus according to Claim 11, wherein the half mask is mounted to the visor.

13. Emergency escape breathing apparatus according to either Claim 11 or Claim 12, wherein a speech diaphragm is mounted in the visor.

14. Emergency escape breathing apparatus according to any one of the preceding claims, wherein the flexible hood further includes a relief valve.

15. Emergency escape breathing apparatus according to any one of the preceding claims,. wherein a neck seal is provided on the interior of the hood for inhibiting ingress of gas into the hood when the hood is enveloping the head of the wearer.

16. Emergency escape breathing apparatus substantially as hereinbefore described with reference to the accompanying drawings.