GB2416701A

GB2416701A - High pressure breathing mask

Info

Publication number: GB2416701A
Application number: GB0417376A
Authority: GB
Inventors: Joseph Anthony Griffiths
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-08-04
Filing date: 2004-08-04
Publication date: 2006-02-08
Also published as: GB0417376D0

Abstract

A breathing mask for supplying pressurised breathable gas to a wearer such as a pilot. The mask comprises an inspiratory valve including a first diaphragm that is normally closed to prevent the flow of pressurised breathable gas into the mask but opens in response to a drop in pressure in the mask that occurs when the wearer inhales to allow breathable gas to flow into the mask through the inspiratory valve from a pressurised breathable gas supply. The mask also includes an expiratory valve including a second diaphragm that is normally closed to prevent the flow of pressurised breathable gas out of the mask but opens in response to an increase in pressure in the mask that acts over one side of the second diaphragm and occurs when the wearer exhales to allow breathable gas out of the mask through said expiratory valve. The second diaphragm is located in a valve housing and the mask includes a pressure compensation tube communicating the supply of pressurised breathable gas with the housing so that pressurised breathable gas acts over the other side of the second diaphragm to bias the second diaphragm into its normally closed state against the pressure of the breathable gas acting on said one side until the wearer exhales to increase the pressure acting on said one side relative to the pressure acting on the other side. The pressure compensation tube runs on the inside of the mask and extends through the first diaphragm to communicate the supply of pressurised breathable gas with said valve housing.

Description

241 6701 - 1 High Pressure Breathing Mask

Description

s The present nveotrr>n relates to a breathing mask for use by pilots and m particular, to fighter pilots' masks operable with a pressurised breathable gas supply and a valve for use therewith.

Conventional breathing equipment for aircrew comprises a mask to fit around the pilot's nose and mouth having an inspiratory valve through which oxygen or some other breathable gas is supplied to the mask and, an expiratory valve through which air is expelled from the mask on exhalation. 'l'he valves commonly comprise a circular stepped diaphragm held over an aperture in a circular valve housing such that the diaphragm is biased against the rim of the circular housing sealing the aperture. 'l'he valves are operated by the pressure changes generated by the plot's breathing - that is to say that when the pilot breathes in, the pressure in the mask drops below the pressure outside the mask and in the breathable gas supply pipe, causing the expiratory valve to be pulled shut and the insprratory valve to open allowing breathable gas to be drawn into the mask. Conversely, when the pilot breathes out, the pressure in the mask is increased above that outside the mask and in the breathable gas supply pipe, pushing the insptratory valve shut and the expiratory valve open so that the exhaled air is expelled from the mask.

lithe above arrangement is fine for pilots' masks in commercial aircraft and low 2s performance aircraft. 1-iowever, high-performance aircraft such as modern fighter lets require more complicated breathing equipment. This is due to the feet that these aircraft are capable of executing manoeuvres which subject the plane and pilot to forces of up to 9G. Uilder these conditions, the pilot must receive breathable gas, possibly with increased oxygen content, at a pressure above that of the cabin pressure to prevent what is known as G-LOC (G-Force Loss Of Consciousness).

the pressurised breathable gas supply is provided by a breathing gas regulator that is responsive to the G-forces that it is subjected to, so that the greater the G-foree, the higher the pressure the gas is supplied at. Pilots also require pressurised - 2 breathng gas supply when flying at high altitude where the ambient air pressure is very low. 1-iowever, If the breathable gas Is supplied to a conventional mask under pressure, the gas m the mask Is at a pressure above that outscle the mask and sc, the exploratory valve Is continually forced open causing a continuous Row of the s breathable gas into and straight out of the mask. C)bvously the mask does not work If this happens and the supply of breathable gas is quickly depleted and the pilot Is deprived of a sufficiently pressurse:l breathing supply, possibly Ieadng to G-l,()C, which In a combat situation, could be fatal.

One possible way to overcome this is to bias the exploratory valve In the closed position so that it is capable of maintaining an elevated pressure within the mask.

However, this will only work If the breathable gas is supplied to the mask at a known and constant pressure so that the strength with which the exploratory valve Is biased closed can be set so that it is lust sufficient for the valve to open when the pilot breathes out and Increases the pressure withy the mask, but ensures that the valve stays closed at all other times.

As described above, the breathable gas Is supplied to the plot's mask by a breathing gas regulator, so the pressure of the gas varies depending on the G-forces that the pilot Is subjected to. 'I'herefore, an expiratory valve that is biased closed with a constant force will not allow the mask to work properly. Therefore, the latest fighter pilot masks employ what is known as a CEV - a 'Compensated Exploratory Valve'. This CEV comprises a chamber behncl the valve diaphragm which is connected to, and therefore at the same pressure as, the pressurised breathable gas supply. The chamber includes means operable to bias the valve diaphragm closed with a force equal to the pressure in the chamber. '[therefore, the expiratory valve is always biased closed with the same force as the pressure of the breathable gas supply, so that the small pressure changes generated within the mask by the pilot breathing in and out are sufOcent for the mspiratory and expiratory valves to work properly as described earlier with reference to the conventional aircrew mask.

There remains the problem with these CEVs of providing a pressure compensation tube from the pressurised breathing gas supply pipe to the CEV to equalise the pressure in the CEV chamber with that of the pressurised gas supply. This Is particularly difficult If the REV is located on the Inside of the tnask, as it requires a separate pressure compensation tube to branch off from the breathing gas supply pipe and pass through the body of the mask to the (.IV. This presents the added s difficulty and expense of manufacturing these complicated devices foe. branched pressure compensation tube from the breathing gas supply pipe, and tube aperture in the mask), cosurng an air-tght seal where the pressure compensations tube branches from the main breathing gas supply pipe and where it passes through the mask to the interior thereof, and the added inconvenience of having the pressure compensation tube on the outside of the mask which could get caught on other objects around the ptlot's head and present a nuisance.

It is therefore an oblect of the present Invention to provide a mask having an inspiratory valve and a pressure compensation tube that will substantially alleviate or overcome the problems mentioned above.

According to the present invention, therefore, there Is provided a breathing mask for supplying pressurtsed breathable gas to a wearer such as a pilot, comprising an inspratory valve including a first diaphragm that Is normally closed to prevent the flow of pressured breathable gas into the mask but opens In response to a drop In pressure In the mask that occurs when the wearer Inhales to allow breathable gas to flow into the mask through the insptratory valve from a pressurised breathable gas supply and, an expiratory valve including a second diaphragm that is normally closed to prevent the flow of pressurised breathable gas out of the mask but opens 2s in response to an Increase in pressure in the mask that acts over one side of the second diaphragtn and occurs when the wearer exhales to allow breathable gas out of the mask through said expiratory valve, the second diaphragm being located in a valve housing and the mask including a pressure compensation tube communicating the supply of pressurtsed breathable gas with the housing so that pressurised breathable gas acts over the other side of the second diaphragm to bias the second diaphragm into its normally closed state against the pressure of the breathable gas acting on said one side until the wearer exhales to increase the pressure acting on said one side relative to the pressure acting on the other side, wherein the pressure compensation tube extends through the hrst diaphragm to communicate the supply of pressursed breathable gas with said valve housing.

In a preferred emboduneot, the first diaphragm Is located In a valve housing s comprising a central support member the pressure compensation tube extending through an aperture m the central support ruember and the hrst diaphragm.

Preferably, the pressure compensation tube includes a tubular pin through which pressurised breathable gas may flow, the pin being located in the aperture In the central support member.

The pin preferably has a shank portion and a head portion, the head portion having a larger cross-sectoned diameter than the shank portion so that the shank portion extends through the aperture In the first diaphragm and central support member to sandwich the first diaphragm between the central support member and the head portion and locate the hrst diaphragm In the valve housing.

In a preferred embodiment, the pin extends all the way through the central support member and end of the pm remote from the head portion Includes means to attach the pin to the central support member. Conveniently, said means includes a threaded section on the pin operable to receive a nut to secure the pin to the central support member of the valve housing. Alternatively, said means may include a snap- fit connector on the pin that cooperates with the central support member to secure the pin thereto. Preferably, the compensation tube is an Interference fit In the aperture m the central support member.

In a preferred embodrnent, the pin is rigid and at least a portion the remainder of the pressure compensation tube is flexible. The compensation tube and hrst valve diaphragm may be integrally formed as one unitary component. Alternatively, the compensation tube and first valve diaphragm may be bonded to each other.

The first and second diaphragms are preferably circular, and the hole in the first valve diaphragm through which the pressure compensation tube extends is preferably formed in the centre thereof. - 5

Convenicntly, the first valve diaphragm Is made of natural or synthetic rubber, and the first valve housing Is advantageously made of a solid plastic material.

s In a preferred embodiment, the pressure compensation tube extends through the inside of the mask between the Aspiratory and expiratory valves, and may be Integrally formed In the mask.

A preferred embodiment of the present Invention will now be described, by way of 0 example only, with reference to Figures 5 and 6 of the accompanying drawings, in which Figure IA Is a schematic cross-sectonal view of a standard prior art mask; Figure 113 Is the mask of Figure IA when a wearer is Inhaling; Figure IC is the mask of Figure IA when a wearer Is exhaling;

Figure 2 is a prior art valve diaphragm;

Figure 3 is a cross-sectonal view of a prior art valve housing and valve diaphragm; Figure 4 is a schematic cross-sectional view of a prior art high-pressure breathing mask; Figure 5 Is a schematic cross sectional view of a breathing mask of the present invention; and Figure G is a cross sectional view of the Aspiratory valve of the mask of the present Invention.

2s Referring now to Figures IA - 1C there Is shown a prior art pilots'nask I comprising a flexible oro-nasal mask 2 having an tnspratory valve 3 and an exploratory valve 4. Each valve 3, 4 has an associated diaphragm 3a, 4a operable to open or close the valve 3, 4 and each valve diaphragm 3a, 4a Is normally biased in the closed position when the pressure inside the mask is equal to the ambient pressure P9mb outside the mask (see Figure IA).

When a pilot wearing the mask breathes in, the pressure Pred Inside the mask is reduced below ambient pressure Limb and so the Aspiratory valve diaphragm 3a is - 6 pulled open (see Figure IB) and air flows Into the mask, shown by arrows A. At the same time, the reduced pressure l'rCd wtthttI the mask exerts a force F.' on the expiratory valve diaphragm 4a pulling it closed, ensuring that the air drawn Into the mask Is tohaled by the pilot and does not escape through the eXpiratQry valve 4. s

On the contrary, when the pilot exhales, the pressure Pins inside the mask is increased above ambient pressure Pub which exerts a force F2 on the inspiratory valve diaphragm 3a pushing it closed, and at the same time the expiratory valve diaphragm 4a is pushed open (see Figure IC) and the exhaled air flows out of the mask, shown by arrows B. The prior art tnspiratory valve 3 and valve diaphragm 3a are shown in more detail In Figures 2 and 3 respectively (although the prior art exploratory valve 4 and valve diaphragm 4a are identical). The valve 3 comprises a valve diaphragm 3a and a valve housing 3b. The diaphragm 3a is a circular stepped disc with a post 5 protruding in an axial direction froth the centre. The post 5 is received In a similarly sized circular aperture 7 In a central portion 6 of the valve housing 3b such that it Is held m place by friction therewith. The valve housing 3b is configured such that when the valve diaphragm 3a is fitted thereto with the post S fully rnsertecl ISI the circular aperture 7, the diaphragm 3a is deflected slightly into a concave forte to make a seal with a peripheral rim 8 of the housing 3b, as shown in Figure 3. '1'hts ensures that the resilience of the valve diaphragm 3a keeps the valve 3 In a normal closed state until acted upon by external pressure forces. As the valve diaphragm 3a is thin and flimsy, the valve housrtlg 3b also includes ribs positioned to support the 2s diaphragm 3a radially midway between the centre of the valve housing 3b at the circular aperture 7 and the peripheral rim 8.

Referring now to Figure 4, a prior art mask I0 is shown which is capable of supplying breathable gas at high pressure to a pilot wearing the mask I0. The mask I0 comprises an oro-nasal mask I I having an inspiratory valve 12 of the type described above with reference to Figures 2 and 3, and a 'Compensated Expiratory Valve' (CEV) 13 as described earlier. The inspiratory valve 12 is connected to a - 7 source of pressursed breathable gas from a breathing gas regulator (not shown) via a supply pipe 14 and all elbow conuectiorl 15.

A pressure comperlsatton tube 16 is connected between the supply pipe 14 and a s compensation chamber 13a of the (REV 13 within the oro-nasal mask 11, and the pressure compensation tube 16 therefore passes through a hole I la In the wall of the oro-nasal mask 11. lion the mask 10 to funeton properly, a secure, air-tight seal So is provided where the pressure compensation tube 16 branches from the supply pipe 14, and another airtght seal S2 is provided where the pressure compensation tube 16 passes through the hole 11a in the oro-nasal mask 11.

In use, when pressurised breathable gas is supplied to the mask through the pipe 14, tile gas Is also supplied at that pressure through the pressure cornpeosatton tube 16 to the compensation chamber 13a of the CEV 13.'1he drapllragm of the ( EV 13 is thereby biased in the closed position with a force equal to that of the pressure of the breathable gas supply, and so small pressure varratlons created inside the oro- nasal mask 1 I caused by the pilot breathing in and out, are sufficient for the inspiratory and expiratory valves 12, 13 to open and close correctly as with a standard (non-high pressure) breathing mask I as described above with reference to Figures IA- 1( . However, it will be appreciated that the arrangement of the mask 1() shown in ligure 4 has a number of significant drawbacks. Firstly, a much more complicated manufacturing process is required to produce a breathing gas supply pipe 14 with a pressure compensation tube 16 branching therefrom, rather than to lust produce a single uninterrupted supply pipe. Secondly, producing the mask 10 with a pressure compensation tube 16 extending through the wall 11a of the oro-nasal mask 11, and ensuring the Integrity of the seal S2 between the oro-nasal mask 11 and the pressure compensation tube 16, as well as the integrity of the seal S' between the supply pipe 14 and the pressure compensation tube 16, results in the overall construction process being complicated, time consuming and expensive.

- -

Furthcrmore, as can he seen from Figure 4, the pressure compensation tube 16 will restrict the freedom of movement of the supply pipe 14 about the elbow 15 relative to the oro-nasal mask 11. Also, if the supply pipe 14 Is tugged too hard, the Integrity of either of the seals S.', 82 could be compromised which would result in the mask not functioning properly to supply pressurised breathable gas to the pilot, which, in a combat or high altitude situation, could have fatal consequences.

Referring now to Figures 5 and 6, a mask 20 of the present invention is provided which is designed to overcome these problems mentioned above. 'lihe mask 20 comprises an oro-nasal mask 21 having an Aspiratory valve 30 and an exptratory valve 50. Pressurised breathable gas is supplied to mask 20 through the inspiratory valve 30 from a breathing gas regulator (not shown) via a supply pipe 24 which Is connected to the inspiratory valve 30 via an elbow joint 25. The elbow joint 25 is rotatably connected to the inspiratory valve 30 by a rotatable air-tght coupling 25a.

As with the prior art high-pressure mask 10 shown in Figure 4, the exploratory valve of the mask 20 of the present invention comprises a CEV 50 having a pressure compensation chamber 51 and a diaphragm 52.

It will be noted from Figure 5 that a pressure compensation tube 2G Is connected at one end to the compensation chamber 51 of the CEV 50 and, at the other end, to the pressursed breathable gas supply within the supply pipe 24. Therefore, the CEV is able to operate as described with reference to the prior art mask calf Figure 4.

I Towever, unlike the prior art mask of l;gure 4, the pressure compensation tube 26 does not branch off from the supply pipe 24, and does not extend through the wall of the oro-nasal mask 21. Instead, the pressure compensation tube 26 extends through the centre of the inspiratory valve 30.

The inspiratory valve 30 used in the mask of the present invention IS shown in more detail in Figure 6, and comprises a valve housing 31 and a valve diaphragm 40. '1'he valve diaphragm 40 sits on the valve housing 31 so as to make a seal with a peripheral rim 32 thereof and is supported at a point 41 md-way along its radius by a circular supporting rib portion 33 of the valve housing 31. The valve diaphragm has a central hole 42 thercthrough which Is in alignment with an aperture 34a in a central portion 34 of the valve housing 31. The valve diaphragm 40 is held in place on the valve housing 31 by a central pm 35. The pin 35 has an enlarged head 36 and a shank 37. The head 36 engages an upper surface 43 of the valve diaphragm near the central hole 42, and the shank 37 of the pin 35 passes through the s central hole 42 In the valve diaphragm 40 and the central aperture 34a in the central portion 34 of the valve housing 31. The free end 37a of the shank 37 remote from the head 36 is threaded to receive a retanmg nut 38 thereon to attach it and the valve diaphragm 40 to the central portion 34 of the valve housing 31. The pin 35 has a hollow bore 39 which extends the whole way through the length of the pin 35 and Is open at both earls thereof. Gas is therefore able to pass through the valve 30 via the hollow bore 39 in the pin 35 even when the valve diaphragm 40 makes a seal with the peripheral rim 32 of the valve housing 31.

lithe pressure compensation tube 2G comprises two separate sections: a first section 26a having one end connected to the pressure compensation chamber Sl of the (TV and the other end connected around the open end of the hollow bore 39 at the head 36 of the pm 35; and a second section 2Gb having one end connected around the open end of the hollow bore 39 at the threaded end 37a of the shank 37 of the pin 35, and the other open end tertnloating a small distance into the elbow joint 25 of the supply plpC 24. The compensation tube 26, in association with the pin 25, is therefore operable to equalise the pressure in the chamber Sl of the CEV SO with the pressure in the supply pipe 24, independently of the operation of the respiratory valve diaphragm 52. As the compensation tube 26 is hidden within the interior of the oro-nasal mask 21/elbow joint 25, it is neatly out of the way and does not need to pass through the wall of the oronasal mask 21 at any point.

In use, pressurisecl breathable gas is supplied to the mask 20 when the pilot executes a high-G manoeuvre or If flying at high altitude, and the high-pressure gas fills the interior of the oro-nasal mask 21. However, the gas also passes from the supply pipe do 24 and elbow Joint 25, through the second part 26b of the compensation tube 26, through the hollow bore 39 of the pin 35, through the first part 26a of the compensation tube 26 and into the compensation chamber Sl of the CEV SO so that the CEV diaphragm 52 is biased in the closed position preventing the pressunscd gas from escaping straight out of the oro-nasal mask 21. Therefore, when the pilot breathes In and out, the inspratory valve 30 and the CEV 50 operate as described earlier with reference to the standard pilots' mask 1. Furthermore, as the G-forces exerted on the plane change and so the pressure at which the breathing s gas regulator supples the breathing gas changes, the pressure is Instantly equalised In the chamber 51 of the CIlV 50 via the compensation tube 26, ensuring that the mask 20 continues to function regardless of the brcathmg gas pressure fluctuations.

Although it would appear that the mask 20 of the present invention would work as described above without the second part 26b of the pressure compcusaton tube 26 extending from the threaded end 37a of the pin 35 into the elbow joint 25, this section 2Gb of the pressure compensation tube 26 prevents pressure fluctuations directly surrounding the mspratory valve Inlet which arc caused by its operation, affecting the CEiV chamber 51 pressure when equalising it with the breathing gas supply pressure.

I'he mask 20 of the present invention has the advantage that it allows the breathing gas supply ppc 24 to rotate through 360 relative to the oro-nasal mask 21 about the coupling 25a of the elbow Joint 25, without the supply pipe 24 being restricted by the pressure compensation tube 26. This is possible because the compcusatlon tube 26 Is fixed relative to the inspfratory valve 30 but is completely independcat from the breathing gas supply pipe 24. This is In contrast to prior art masks in which the compensation tube branches off from the breathing gas supply tube and passes through the wall of the mask, and so movement of the breathing gas supply tube Is restricted by the compcosation tube pulling at the mask, which Is distracting for the pilot and can cause the mask to come away from the pilot's face allowing the pressurised breathing gas to escape.

Although the embodiment of the inspiratory valve 30 of the invcotion described above incorporates a pin 35 that has a threaded portion 37a to receive a nut 38 to hold it in place, other alternative means to attach the pin 35 to the valve housing 31 are possible within the scope of the invention. For example, the pin 35 may include a snap-fit connection at the end of the shank 37 remote from the head 36 to engage - 11 wlth the edge of the central aperture 34a in the central portion 34 of the valve housrlg 31. Alternatvcly, the diaphragm 40 and pressure compensation tube 2G could be formed as one unitary item, the cotn,tensation tube 26 passing through the central aperture 34a In the central portion 34 of the valve housing 31 and being held s In position by friction therewith, and extending from within the supply ppc 24/elbow joint 25 outside the oro-nasal mask 21 to the CI2V 50 Inside the mask 20. - 12

Claims

Claims 1. A breathing mask for supplying pressursed breathable gas to a

wearer such as a pilot, comprising an respiratory valve Including a first diaphragm that Is s normally closed to prevent the flow of pressurtsed breathable gas Into the mask but opens in response to a drop ill pressure In the mask that occurs when the wearer inhales to allow breathable gas to flow Into the mask through the inspiratory valve from a pressurtsed breathable gas supply and, an expiratory valve including a second diaphragm that is normally closed to prevent the flow of pressurised breathable gas out of the mask but opens In response to an increase in pressure in the mask that acts over one side of the second diaphragm and occurs when the wearer exhales to allow breathable gas out of the mask through said exploratory valve, the second diaphragm being located in a valve housing and the mask including a pressure compensation tube communicating the supply of pressurtsed breathable gas with the housmg so that pressursed breathable gas acts over the other side of the second diaphragm to bias the second diaphragm into its normally closed state against the pressure of the breathable gas acting on said one side until the wearer exhales to increase the pressure acting on said one side relative to the pressure acting on the other side, wherein the pressure compensation tube extends through the first daphragtll to communicate the supply of pressurtsed breathable gas with said valve housing.

2. A mask according to claim I wherein the first diaphragm is located In a valve housing comprising a central support member the pressure compensation tube extending through an aperture in the central support member and the first diaphragm.

3. A mask according to claim 2 wherein the pressure compensation tube includes a tubular pin through which pressurised breathable gas may flow, the pin being located in the aperture in the central support member.

4. A mask according to claim 3 wherein the pin has a shank portion and a head portion, the head portion having a larger cross-secttoned diameter than the shank - 13 portion so that the shank portion extends through the aperture in the first diaphragm and central support memller to sandwich the first diaphragm between the central support meml>er and the head portion and locate the first diaphragm in the valve housing.

5. A mask according to claim.3 or claim 4 wherein the pm extends all the way through the central support member and end of the pin remote from the head portion includes means to attach the pin to the central support member.

G. A mask according to claim 5 wherem said means includes a threaded section on the pin operable to receive a nut to secure the pin to the central support member of the valve housing.

7. A mask according to claim 5 wherein said means includes a snap-fit connector on the pin that cooperates with the central support member to secure the pin thereto.

8. A mask according to any of claims 2 to 4 wherein the compensation tube is an interference fit in the aperture in the central support member.

9. A mask according to any of claims 3 to 7 wherein the pin is rigid and at least a portion the remainder of the pressure compensation tube is flexible.

10. A mask according to claim 1 wherein the compensation tube and first valve 2s diaphragm are integrally formed as one unitary component.

11. A mask according to claim 1 wherein the compensation tube and first valve diaphragm are bonded to each other.

12. A mask according to claim any preceding claim wherein the first and second diaphragms are circular. - 14

t3. A mask according to claim 12 wherein the hole in the first valve diaphragm through which the pressure compensation tube extends Is formed In the centre thereof.

s 14. A mask according to any preceding claim wherem the first valve diaphragm Is made of natural or synthetic rubber.

15. A mask according to any preceding claim wherein the first valve housing is made of a solid plastic material.

16. A mask according to any preceding claim wherem the pressure cotupensaton tube extends through the inside of the mask between the inspiratory and expiratory valves.

17. A mask according to claim 16 wherein the pressure compensation tube is integrally formed m the mask.

18. A tnask substantially as hereinbefore described with reference to the accompanying drawings.