WO1997021466A1

WO1997021466A1 - Breathing apparatus and nozzle therefor

Info

Publication number: WO1997021466A1
Application number: PCT/GB1996/003023
Authority: WO
Inventors: Peter David Grayson
Original assignee: Geo Limited
Priority date: 1995-12-08
Filing date: 1996-12-09
Publication date: 1997-06-19
Also published as: GB9525097D0; AU1383997A

Abstract

A breathing apparatus and a nozzle for use in a breathing apparatus is provided by the present invention. In use, filtered air flows along passageway (31) of the nozzle and a first air flow for breathing flows out of a first outlet (23). A second outlet (25) allows outflow of a second air flow which establishes a gas curtain outwardly of the first air flow. The gas curtain substantially reduces the breathing of contaminated atmospheric air by the wearer. The apparatus and nozzle have particular application for cyclists, asthma sufferers, etc.

Description

Breathin^g a^pparatus and nozzle therefor

The present invention relates to a breathing apparatus and also to a nozzle for use in a breathing apparatus.

Many different types of breathing masks are known that

completely cover the face and prevent particles present in the

atmosphere from reaching the respiratory system of the wearer. Such masks are unsightly and in many applications provide unnecessary, i.e. excessive, protection. Thus, for example, people who suffer from

hay fever and asthma can relieve the symptoms of their complaint to a substantial extent by reducing the amount of particles in the air they breathe without completely eliminating such particles.

Breathing apparatuses are also known that do not completely

cover the face. For example, in the Mining Engineer No. 209, page 559 there is described a breathing apparatus in the form of a helmet having a transparent visor located in front of the face. Clean air is blown through the helmet down the inside of the visor and escapes

to atmosphere around the bottom edge of the visor. The air supplied in this way firstly provides clean breathable air and secondly provides a positive gas pressure in front of the face that prevents particles in the air from reaching the face.

An alternative type of breathing apparatus is described in CIM

Bulletin April 1979, page 149. This apparatus also uses a helmet but

in this case the transparent visor is dispensed with and a fast-flowing curtain of air is established in front of the wearer's face to provide

clean breathing air and to provide a barrier against atmospheric

particles.

These types of breathing apparatus are again unsightly and at

least the apparatus described in the CIM article uses a large amount

of air which requires a large amount of power to move it.

Furthermore, the flow of gas establishing the barrier against

atmospheric particles is uncomfortable when it impinges against the

face.

The present invention provides a breathing apparatus that can

be more sightly than a face-enclosing mask and that provides clean

breathable air and a barrier against atmospheric particles without

requiring a visor or a curtain of fast moving gas impinging on the face.

According to a broad aspect of the present invention, there is

provided a breathing apparatus comprising a nozzle, means for

supplying air to the nozzle and means for positioning the nozzle in

front of the nose/mouth region of a wearer's face, the apparatus

being such that it does not enclose the face.

According to a second aspect of the present invention, there is provided a nozzle for use in a breathing apparatus, the nozzle

comprising at least one inlet for air and at least one outlet in

communication with an inlet for providing a flow of air which

generates a positive air pressure in front of the nose/mouth region of the face of a wearer, in use. This flow provides air for breathing, whilst also generating a gas curtain which provides a barrier to atmospheric air and thus substantially prevents the wearer from breathing atmospheric particles contaminating the atmospheric air. Preferably the nozzle comprises at least one inlet for air, at

least one first outlet in communication with an inlet for providing a first flow of air, and at least one second outlet also in communication with an inlet for providing a second flow of air. Advantageously, the outlets are arranged such that, in operation, the second flow is

located outwardly of the first flow. Most preferably one flow of air provides air for breathing, whilst the other flow establishes a gas curtain.

Preferably, in use, the first flow is directed onto the nose/mouth region of the face to provide breathing air while the second flow establishes a gas curtain outwardly of the first flow and prevents, or at least reduces, the number of atmospheric particles

being breathed. The second flow of air may be generally conical, in which case the second outlet is usually annular in shape, or it may be made up of two or more generally planar flows each issuing from a slot-shaped orifice. If more than one inlet is provided for air, the air supplied to each inlet may be from a single source or from more than one source,

depending upon the particular circumstances. The advantages of having more than one inlet for air include that only the air supplied to the inlet(s) in communication with the outlet(s) for providing the

breathing air needs to be filtered. This filtering may occur either at

source or at any stage(s) along the pathway from the source to the

nose/mouth region of the face of the wearer, in use. For example, the

or each first outlet may be in communication with a first inlet and the

or each second outlet may be in communication with a second inlet.

In such circumstances, most preferably the first inlet is supplied with

filtered air.

In order to increase the comfort of the breathing apparatus

while improving its effectiveness in eliminating atmospheric particles,

the first flow is preferably slower than the second flow. This is

preferably achieved by placing a flow-resistance, e.g. a gauze, screen

or mesh, in the path of the air flowing to or through the or each first

outlet while allowing the air to flow freely from the inlet to and

through the or each second outlet. Alternatively, the velocity of the

first flow may be altered by a suitable choice of outlet diameters, by providing a curved or sinuous flow path for air from the inlet to the or

each first outlet or by generating turbulence in air travelling to or

through the or each first outlet. Also, the air flowing to and through

the or each second outlet need not flow freely but may be slowed

down or accelerated if desired, e.g. by means of a Venturi

constriction. The second flow is preferably not directed at the face but flows

generally parallel to its contours. This prevents discomfort caused by

a fast second stream impinging on the wearer's face.

In a preferred embodiment the air flows to the or each second

outlet along a duct provided with a port leading to the atmosphere,

the arrangement being such that air flowing through the duct induces

a flow of atmospheric air through the port thereby increasing the

amount of air in the second stream. Since the main function of the

second stream is to provide a barrier against the approach of

atmospheric air to the nose/mouth region, rather than providing air

that is breathed, the presence in the second stream of some atmospheric air can be tolerated.

Ten nozzles according to the present invention will now be

described, by way of example only with reference to the

accompanying drawings, in which:-

Figure 1 shows a schematic representation of the operation of

the nozzles,

Figures 2 to 1 1 show sectional elevations of the ten nozzles.

Figures 1 2 and 14 are schematic diagrams of an apparatus for testing the efficiency of nozzles and

Figures 13 and 15 are graphs showing the efficiency of various

nozzles.

Referring firstly to Figure 1 , a nozzle is indicated with the reference numeral 10. The nozzle is supplied with clean air along a duct (not shown) from a supply unit (again not shown) which is

preferably a portable battery-powered device that draws in atmospheric air and filters or precipitates the suspended particles e.g. by electrostatic precipitation and/or by a carbon filter, to produce air with almost no suspended particles greater than between 10 microns

and 0.04 microns. Such devices are known rjer se. The nozzle is held in place in front of the nose/mouth region by the duct which in turn is attached to the wearer by a clip that is hooked over one or both ears or by a resilient head band.

The nozzle 10 produces a first flow of air (shown by arrows 1 1 ) that is breathed. It also produces a second flow (shown by arrows 12) in the form of a curtain of fast-flowing air that prevents contaminated atmospheric air from reaching the wearer as shown schematically by arrows 13. It will be noticed that the second stream does not impinge on the wearer's face and hence does not cause discomfort. A mixture of exhaled air, unbreathed air from the first stream and some air from the second stream forms a region of gas 14

at a pressure that is slightly higher than atmospheric pressure and hence reduces the amount of contaminated atmospheric air (shown by arrows 15) reaching the wearer. As will be observed from Figure

1 , the high pressure region 14 is bordered by the second air stream 12 from the nozzle 10, which prevents air in the region from crossing it, thereby increasing the pressure in the region 14.

Referring firstly to the nozzle shown in Figure 2, it has an inlet

passage 21 for filtered air (shown schematically by arrows 22). At

the end of the inlet passage, there is a first outlet 23 covered with a

flow-resistive mesh 23a e.g. made of cotton gauze, plastics metal

such as stainless steel or any other appropriate material. Extending

around the first outlet 23 is a conical passage 24 leading to an

annular second outlet 25. Due to the gauze placed in the first outlet

or size of aperture of the first outlet, the velocity of the air leaving the

first outlet is less than that leaving the second outlet and the latter

forms a conical current of fast-flowing air that acts as a diffusion

barrier against atmospheric air as described above. The volume of

fast-moving air is augmented by atmospheric air drawn into the

conical passage 24 through ports 27. Atmospheric air is drawn into

the passage 24 by the flow of filtered air therethrough and thus the

curtain of fast-moving air is a mixture of filtered air from inlet passage

21 and air drawn in through ports 27. The velocity of the air leaving

the first outlet 23 is sufficiently low that it is not uncomfortable to the

wearer.

The nozzle shown in Figure 3 differs from that shown in Figure

2 only in that walls 26 of the cone are not impermeable but are

porous, preferably by providing them as a meshed region. The mesh

may be of variable porosity across its surface. In this embodiment of nozzle the flow resistive mesh 23a covering the first outlet 23 may be of different porosity from that of the mesh wall 26 or may be absent.

Features that are the same in Figures 2 and 3 are shown by the same reference numerals.

It will be appreciated that the nozzle may be of any suitable geometry but, by way of example only the geometry of the nozzle

(with reference to that in Figure 3) may be as follows. The diameter of the passageway 21 is preferably between 5 and 20 mm. The length of walls 35 extending from the walls of passageway 21 is preferably between 2 and 50 mm. The first outlet 23 is preferably up

to 20 mm in diameter. The width of the duct 24 leading to the second outlet 25 is preferably between 0.2 and 5mm. The walls of the duct are not necessarily parallel such that the width of the duct 24 may vary along its length. The velocity of the first flow of air as

for a nozzle of such dimensions is generally between 10 litres/min to 250 litres/min.

The nozzles shown in Figures 4 and 5 differ from those shown in Figures 2 and 3 respectively only in that the inlet passage 31 is

bent to facilitate its location in front of the wearer's face and in that they do not possess the ports 27, although, of course, such could be

included. The curved shape of the inlet passage generates turbulence in the air flowing through the passage 31 as indicated by arrows 22a in Figure 5. The turbulence generated optimises the even distribution of air-flow to the first and second outlets and thus assists in

optimising the efficiency of the nozzle. Features in Figures 4 and 5

that are the same as those in Figures 2 and 3 respectively are shown

by the same reference numbers.

Figure 6 shows a nozzle as shown in Figures 4 and 5 but

including a mesh pressure diffuser 28 spanning the inlet passage 31 .

The walls 26 may be impermeable or porous as in the previous

embodiments shown.

In a further embodiment of nozzle as shown in Figure 7, the

wall 26 extends inwardly effectively segmenting the inner

passageway 31 into a central passageway 29, leading to the first

outlet 23, and a substantially annular outer passageway 30 leading to

the second outlet 25. Of course, it will be appreciated that the

passageway 29 may be displaced to one side in certain embodiments.

Alternatively passageway 29 could comprise a tube supported within

the inner passageway 31 by supports (not shown) extending from the

inner surface of the inner passageway 31 . By segmenting the inner

passageway 31 in this manner the efficiency of the nozzle is

optimised by optimising the even distribution of the air flow to and

through the first and second outlet(s) . The first outlet 23 could be

covered by a mesh, gauze or the like in certain embodiments.

Figure 8 shows a still further embodiment of nozzle according

to the present invention having air flow deflectors 32 located within the passageway 31 . The deflectors, such as ribs upstanding from the

inner surfaces of the passageway 31 , assist in optimising the efficiency of the nozzle by optimising the even distribution of the air flow to and through the first and second outlet(s).

The embodiment as shown in Figure 9 has particular application

for circumstances where the wearer requires increased protection.

The nozzle has extensions 34 which provide a physical barrier in addition to the gas curtain (provided by the second air flow from the second outlets) thus increasing the avoidance of contaminated atmospheric air from reaching the wearer. The extensions may be integral with the nozzle or may be provided as a removable attachment for the nozzle. This embodiment is particularly useful for cyclists where increased wind disturbance velocities during cycling could disrupt the protective barrier provided by a gas curtain alone. Again, as in the previous embodiments, the walls 26 could be impermeable or porous.

The nozzle shown in Figure 10 has a side inlet passage 41 leading to a hemispherical chamber 42 having a first outlet 43 and a second outlet 44 at opposed ends of the chamber. Across the first outlet 43 is a flow-resistive mesh held in place by a multi-armed spider 45 which also serves to support a post 46 within the chamber

42. The post 46 extends through the second outlet 44 and has a head portion 47 which guides air leaving the second outlet along the outer face of the chamber 42. The flow of air hugs the outer face of

the chamber 42 (by virtue of the Coanda effect) and thus forms a

conical fast-moving stream of air (shown by arrows 48) that acts as

a diffusion barrier as described in connection with Figure 1 .

The nozzle shown in Figure 1 1 has an air inlet passage 51

formed in a tube 52. Arranged within the tube 52 is a second tube

53 having an open end 54 for receiving filtered air and a first outlet

55 covered with a flow-resistive screen 56. Two slot-shaped second

outlets 57 are provided in the first tube 52, one slot being arranged

on each side of the first outlet 55, the second outlets each providing

a generally planar stream of fast-flowing air that acts as a diffusion

barrier against atmospheric air as described above.

Although the term 'air' has been used throughout this

specification, it will be understood that any oxygen-containing gas

could be used and instead of being drawn from the atmosphere it

could be supplied from suitable containers e.g. compressed gas

cylinders, although the latter are disadvantageous because of their

weight. The air may also be humidified and/or heated to reduce the

discomfort of air flows in the vicinity of the face, and/or to relieve the

symptoms of bronchitis or non-allergic asthma.

Figure 1 2 is a schematic diagram of an apparatus for testing

the nozzles shown in Figures 2 through to 1 1 . A dummy head 61 is

located inside a chamber 62 and air can be caused to be inside the chamber 62 by a pump 63 thereby simulating various wind conditions. Air is drawn through passageways in the dummy head by

pump 64 to simulate respiration. Part of the air drawn in this manner is discharged through outlet 65 but part passes to a flame photometer 66. A flow meter 67 and a valve 68 are located in the passageway between the dummy head 61 and the pump 64. The flow meter measures the velocity of air drawn in through the valve 68 and the valve enables an environmental sample to be drawn through a tube 69 located in front of the dummy head and analyzed by the flame photometer 66. A nozzle 70 according to Figures 2 to 1 1 is placed

directly in front of the dummy head 61 and fed with air from a supply

71 . An atomised stream of sodium chloride is fed into the chamber 62 from a source 72 and a supply of smoke is fed into the chamber 62 through a diffuser 72 so that the air flow around the dummy head

can be observed. The amount of sodium chloride drawn in through the dummy head passageways is analyzed in the flame photometer 66 and the reading thus obtained is compared with the reading obtained from the analysis by the flame photometer 66 of air drawn through tube 69. The values so obtained give a measure of the protection efficiency of the nozzles. It will be appreciated that smoke is not fed through the diffuser 73 when the flame photometer is being used to analyze air drawn through the dummy head 61 or tube 69 because the smoke might affect the readings obtained. Figure 13 is a graph showing the protection efficiency of each

tested nozzle (y-axis) against the flow rate of air drawn in through the

dummy head, i.e. the simulated breathing rate (x-axis). Curves A, B

and C show the protection achieved by the nozzles shown in Figures

2, 10 and 4 (respectively). The tests were conducted in a still air

environment, i.e. with pump 63 switched off.

From the graph, it can be seen that protection efficiencies of 60

to 85% can be achieved by those nozzles of the present invention

shown in Figures 2, 10 and 4 at the respiratory base rate, i.e. the

normal breathing rate of a person at rest, and that remarkably good

protection is provided even at simulated breathing rates as high as 60

litres/minute.

Figure 14 is a schematic diagram of an apparatus for testing

the nozzles in accordance with European Standards. The test is

conventionally known as a "Total Inward Leakage" test. An

individual 75 stands on a treadmill 76 located inside an enclosure 77.

Air containing atomised sodium chloride is fed into the enclosure

through a duct 78. The mean sodium chloride concentration within

the effective working volume of the enclosure is most preferably 8

( + 4) mg/m³. The conditions of the test may be varied. For example

the individual may be walking, running, talking (as appropriate) and/or

the fan 90 may be switched on to blow a current of air towards the

individual. Samples of air are drawn from the breathing zone of the individual and the enclosure by action of the pumps 79. The samples

are analysed by flame photometry to determine and compare the concentration of sodium chloride in the air flow in the enclosure around the individual and in the breathing zone. The values so obtained give a measure of the protection efficiency of the nozzles.

The protection efficiency of the nozzles can be analysed for different circumstances for example standing, walking, talking etc.

Figure 15 is a graph illustrating the protection efficiency of a nozzle as shown in Figure 3 (y- axis) tested in accordance with the procedure represented by Figure 14 with the individual in a standing,

walking and talking condition (x-axis). It can be seen that the protection efficiency of this nozzle ranges from 66% - 82% depending on the activity of the individual.

Claims

1 . A nozzle for use in a breathing apparatus, the nozzle comprising at least one inlet for air and at least one outlet in communication with an inlet for providing a flow of air wherein the

flow of air generates a positive air pressure in front of the nose/mouth region of the face of a wearer, in use.

2. A nozzle for use in a breathing apparatus according to claim 1 wherein the nozzle comprises at least one inlet for air, at least

one first outlet in communication with an inlet for providing a first flow of air and at least one second outlet also in communication with an inlet for providing a second flow of air.

3. A nozzle according to claim 2 wherein the outlets are arranged such that, in use, the second flow of air is located outwardly of the first flow.

4. A nozzle according to claims 2 or 3, wherein in use, the first flow is directed onto the nose/mouth region of the face of a wearer to provide breathing air and the second flow establishes a gas curtain outwardly of the first flow.

5. A nozzle according to any of claims 2, 3, or 4 wherein the or each first outlet is in communication with a first inlet and the or each second outlet is in communication with a second inlet.

6. A nozzle according to claim 5 wherein a separate source of air supplies each inlet.

7. A nozzle according to claim 5 or 6 wherein at least the

first inlet is supplied with filtered air.

8. A nozzle according to any of claims 2 - 7 wherein the

first flow is slower than the second flow.

9. A nozzle according to claim 8 wherein a flow-resistor is

located in the path of the air flowing from the inlet to and/or through

the or each first outlet.

10. A nozzle according to claim 9 wherein the flow-resistor

comprises a gauze, screen or mesh.

1 1 . A nozzle according to claim 8 wherein the air flow to

and/or through the or each second outlet is accelerated by a Venturi

constriction.

1 2. A nozzle according to any of claims 2 - 1 1 wherein the

second flow of air is generally conical.

1 3. A nozzle according to claim 1 2 wherein a second outlet

is substantially annular.

14. A nozzle according to any of claims 2 - 1 1 wherein the

second flow of air comprises two or more generally planar flows of

air.

1 5. A nozzle according to claim 1 4 wherein each second

outlet comprises a slot-shaped orifice.

16. A nozzle according to any of claims 2 - 1 5 wherein the

air flows from an inlet to the or each second outlet along a passageway.

17. A nozzle according to claim 16 wherein the or each passageway has at least one port in communication with the atmosphere, the arrangement being such that the air flowing to the

or each second outlet along the passageway draws a flow of atmospheric air through the port into the passageway thereby increasing the amount of air in the second flow from the second outlet(s).

18. A nozzle according to any of claims 2 - 17 wherein, in use, the second flow of air is generally parallel to contours of the face of a wearer.

19. A nozzle according to any preceding claim wherein the

flow path for air from the or each inlet to at least one outlet is substantially curved.

20. A nozzle according to claim 19 when dependent on claim 2 wherein a curved passageway is provided from an inlet to at least the or each first outlet.

21 . A nozzle according to any preceding claim wherein the nozzle is supplied with filtered air.

22. A breathing apparatus comprising a nozzle, means for supplying air to the nozzle and means for positioning the nozzle in front of the nose/mouth region of the face of a wearer in use, the apparatus being such that it does not enclose the face.

23. A breathing apparatus according to claim 22 wherein the nozzle comprises a nozzle according to any of claims 1 - 21 .

24. A nozzle substantially as hereinbefore described with reference to the accompanying Figures 2 - 1 1 .