GB2209123A - Breathing apparatus - Google Patents

Abstract

Emergency, closed-circuit breathing apparatus comprises a hood (10) adapted to enclose the head and seal around the neck of the user and enclosing an ori-nasal mask (16) connected to an air supply (22) such as a potassium superoxide chemical oxygen supply. In order to avoid the possible dangers of air escaping from the closed-circuit into the hood (10), the ori-nasal mask (16) is provided with a normally closed valve (38) interconnecting the interior of the mask (16) and the interior of the hood (10). The valve (38) is adapted to open in response to a reduced pressure inside the mask (16) such that the hood (10) acts as an auxiliary, emergency breathing bag. Details of preferred valves are also described. <IMAGE>

Description

Breathing Apparatus The present invention relates to breathing apparatus and is particularly concerned with a closed circuit breathing apparatus, utilising a hood which completely encloses the head of the User, of a type suitable for emergency use in an aircraft or the like.

Emergency breathing apparatus is known which provides clean air and protects against the inhalation of smoke and other fumes. One form of known apparatus is of a closed circuit type and comprises a hood, which encloses the wearer's head and seals around the neck, a breathing bag and a chemical oxygen source communicating with the interior of the hood. This might suitably be a potassium superoxide canister which generates oxygen from exhaled carbon dioxide and water vapour. With a closed circuit system it is important that gas is not allowed to escape from the circuit since this will result in a reduction of the amount of breathing air available and may eventually lead to the possibility of suffocation. For this reason most known systems of this type use a mouthpiece and nose clip which allow virtually no losses from the circuit.This is acceptable for safety professionals such as firemen, however it is not suitable for relatively untrained personnel, and is also unsuitable for aircrew members who may have to communicate with colleagues or issue instructions to passengers. In such cases it would be desirable for the apparatus to incorporate an ori-nasal mask with a speech diaphragm, however the use of an ori-nasal mask in a closed circuit system with a sealed hood presents a serious disadvantage. The pressure of exhalation into an ori-nasal mask tends to break the seal of the mask around the wearer's nose and mouth, allowing gas to escape from the breathing circuit into the hood. This lost gas is unlikely to reenter the system since subsequent inhalation will tend to enhance the seal of the mask.Accordingly, there will be a progressive depletion of breathing air from the circuit which might eventually lead to suffocation as described above.

It is an object of the present invention to obviate or mitigate the aforesaid disadvantage.

Accordingly, the invention provides breathing apparatus including means, such as a hood or the like, adapted to sealably enclose the user's head and having an ori-nasal mask, connectable to a closed circuit air supply, located in the interior thereof, said ori-nasal mask being provided with valve means communicating with the interior of said hood or the like and adapted to open in response to reduced pressure inside said ori-nasal mask.

The term "air" is used to denote breathable gas including oxygen and mixtures of oxygen and nitrogen other than natural air.

The valve means is preferably of a type which provides a relatively high flow rate immediately upon opening.

Preferably also, the ori-nasal mask is further provided with a speech diaphragm.

In a particularly preferred embodiment of the invention the valve means of the apparatus is adapted to be manually operable such that the user can open the valve if necessary.

The provision of the valve means in the or i-nasal mask allows relatively clean air to enter the closed breathing circuit from the interior of the hood in the event that the volume of air within the circuit becomes seriously depleted, so avoiding the danger of suffocation. The invention thus allows an or i-nasal mask to be used safely in a closed circuit breathing system allowing a speech diaphragm to be utilised and so permitting the wearer to communicate freely by direct speech or by means of a loud-hailer or public address handset.

An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings in which, Fig. 1 is a schematic representation of a breathing apparatus embodying the invention; Fig. 2 is an end view of a valve forming part of the apparatus of Fig. 1; Fig. 3 is a section on line III-III of Fig. 2; Fig. 4 is an end view of a modified valve for use in a particularly preferred embodiment of the invention; and Fig. 5 is a section on Line V-V of Fig. 4.

Referring now to Fig. 1 of the drawings, a breathing apparatus comprises a hood 10 of flexible material having a transparent visor 12 and a membrane 14 of elastic material which in use seals around the wearer's neck. Positioned within the hood 10 below the visor 12 is an ori-nasal mask 16 of flexible material such as rubber which in use covers and seals around the nose and mouth of the wearer.

Adjustment straps 18 on the exterior of the hood 10 serve to locate and retain the ori-nasal mask 16 in use.

The mask 16 forms part of a closed circuit breathing system and is connected by a flexible tube 20 to an air supply 22. In this example the air supply 22 is a conventional chemical oxygen supply comprising an insulated potassium superoxide (K02) canister 24 and a quick start chlorate candle 26 (operable by means of a chain-pull 28) enclosed by a mesh screen 30 inside a breathing bag 32 of flexible material. In use, the chlorate candle 26 provides an initial supply of oxygen and the user inhales and exhales through the KO2 canister 24 via a heat exchanger 34. The KO2 canister generates breathable oxygen from exhaled carbon dioxide and water vapour. A relief valve 36 in the side of the bag opens to release the pressure inside the bag 32 in the event of overproduction of oxygen.

In order to allow the or i-nasal mask 16 to be used safely with a closed circuit breathing system of this type, an anti-suffocation valve 38 is provided in one sidewall thereof interconnecting the interior of the mask 16 and the interior of the hood 10. The valve 38 is closed in normal use and opens in response to a reduced pressure inside the mask 10 when a predetermined pressure difference across the valve is exceeded to allow gas from inside the hood 10 to enter the circuit of the breathing system. The hood 10 thus acts as an emergency auxiliary breathing bag. The valve 38 is preferably of a type which opens substantially to its maximum extent as soon as the predetermined pressure difference is exceeded.

A suitable valve 38 is shown in Figs. 2 and 3 and comprises a generally cylindrical casing 40 having an inlet end 42 (as seen in the view of Fig. 2) which faces the interior of the hood 10, and an outlet end 44 which faces the interior of the mask 16. The outlets 44 of the valve 36 is closed by an end wall 46 having a central aperture 48, and a plurality of outlet apertures 50 are provided around the circumference of the casing 40 adjacent the end wall 46.

The valve 36 is closed by a disc shaped member 52 which sealing engages a circumferential shoulder 54 on the interior of the casing between the inlet end 42 and the outlet apertures 50 and is biased into the closed position, as illustrated, by a spring or other bias means (omitted for the sake of clarity). A pin 56 extends from the centre of the disc 52 along the central axis of the casing 40 and slidably engages a bore 58 formed in a bush 60 at the mid point of a diametrical web 62 extending across the inlet end 42.

When the pressure at the outlet end 44 of the valve 46 drops and the predetermined pressure difference is exceeded, the disc 52 moves to the right (as seen in Fig. 3) to abut the end wall 46, thus allowing the inlet end 42 to communicate with the outlet apertures 50. The rim of the casing 40 at the outlet end 42 is preferably provided with a plurality of recesses 64 around its circumference to prevent the inlet becoming sealed in the event that the flexible material of the hood 10 is pressed against it. The valve 36 is located in an aperture (not shown) in the wall of the mask 16 such that the edge of the aperture sealingly engages a circumferential groove 66 formed in the casing 40.

The ori-nasal mask 16 may be further provided with a speech diaphragm 68 which projects through the front of the hood 10 to allow the wearer to communicate with other persons.

Figs. 4 and 5 illustrate a modified valve 69 for use in a particularly preferred embodiment of the invention.

The valve 69 again comprises a generally cylindrical casing 70 having an inlet end 72 and an outlet end 74. As before, the outlet end 74 is closed by an end wall 76 having a central aperture 78, and a plurality of outlet apertures 80 are provided around the circumference of the casing 70 adjacent the end wall 46. The disc shaped member 52 sealingly engages circumferential shoulder 54 on the interior of the casing between the inlet end 72 and the outlet apertures 80, and is again biased into the closed position, as illustrated, by a spring or other bias means (omitted for the sake of clarity). The pin 86 extends from the centre of the disc 52 and is slidable in bore 88 formed in the bush 90 at the mid point of diametrical web 92.

In order to make the valve 69 manually operable, the pin 86 is lengthened such that it extends beyond the web 92 when the valve 69 is closed, thereby allowing the pin 86 to be depressed manually against the force of the bias means to open the valve 69. The outer end of the pin 86 may be provided with a button 94 to facilitate manual operation.

The extended end of the pin 86 may be protected from accidental depression (eg by being impinged upon by the hood 10 of the breathing apparatus by extending the inlet end 72 of the casing 70 beyond the web 92 to surround it.

A further modification is the provision of a plurality of apertures 96 spaced around the circumference of the casing 70 adjacent the inlet 72. These apertures 96 replace the recesses formed around the rim of the casing in the valve 38 of Figs. 2 and 3, and may also be incorporated therein.

The invention also allows an ori-nasal mask to be used safely with any closed-circuit breathing system and sealed hood and also allows a speech diaphragm to be incorporated into the apparatus.

Claims (13)

Claims

1. Breathing apparatus including means adapted to sealably enclose the user's head and an ori-nasal mask, connectable to a closed circuit air supply, located in the interior thereof, said ori-nasal mask being provided with valve means communicating with the interior of the headenclosing means and adapted to open in response to reduced pressure inside said ori-nasal mask.

2. Breathing apparatus as claimed in claim 1 wherein said valve provides a relatively high flow rate immediately upon opening.

3. Breathing apparatus as claimed in claim 1 or claim 2 wherein said ori-nasal mask is further provided with a speech diaphragm.

4. Breathing apparatus as claimed in any of claims 1, 2 or 3 wherein said head-enclosing means is a hood of flexible material.

5. Breathing apparatus as claimed in any preceding claim, wherein said valve means is adapted to be manually operable.

6. Breathing apparatus as claimed in any preceding claim, wherein said valve means comprises a generally cylindrical casing having an inlet end and an outlet end, said casing, in use, extending through said ori-nasal mask such that said inlet end is located on the exterior and said outlet end on the interior thereof.

7. Breathing apparatus as claimed in claim 6 wherein said casing includes an internal, circumferential shoulder formed adjacent said outlet end, and at least one outlet aperture formed in the wall thereof between said shoulder and said outlet end, the valve further including closure means comprising a disc located between said shoulder and said outlet end and biased towards a first position wherein it sealingly engages said shoulder, the disc being movable to a second position, in response to a reduced pressure at the outlet of the valve, wherein said outlet apertures lie between said disc and said shoulder.

8. Breathing apparatus as claimed in claim 7 wherein a pin extends from the centre of said disc perpendicular thereto, and is slidably received in a bore formed in a web extending across the interior of said casing between said shoulder and said inlet end.

9. Breathing apparatus as claimed in claim 8 wherein said pin, when said disc is in its first position, extends through said web and a free end thereof projects beyond said web sufficiently to allow said disc to be manually moved to its second position by applying a force to said free end of said pin.

10. Breathing apparatus as claimed in claim 9 wherein the inlet end of said casing extends beyond the free end of said pin when said disc is in its first position.

11. Breathing apparatus as claimed in any of claims 6 to 10 wherein said casing is open at its inlet end and is provided with a plurality of recessed portions spaced around the rim thereof.

12. Breathing apparatus as claimed in any of claims 6 to 10 wherein said casing is provided with at least one aperture extending therethrough adjacent said inlet end.

13. Breathing apparatus substantially as hereinbefore described with reference to the accompanying drawings.