EP0632736B1 - Breathing apparatus for respiratory protection - Google Patents

Abstract

Breathing apparatus to provide respiratory protection having an outer hood, an inner hood, a reservoir at positive pressure, a breathable gas source and a conveyance means with one way valves in an open circuit system.

Description

This invention relates to breathing apparatus for respiratoryprotection of civilians and combatants.

Early types of breathing apparatus include a flexible hood with avisor for aviators (F741127) and a rigid helmet with a glasswindow for divers (GB426962), both with a remote breathable gassupply. More recently, various types of portable breathingapparatus have been described. A simple transparent bag with aneck seal and a filter is known (GB 2129670A) but the design isdefective due to a large effective dead space. The deficiencymay be overcome by incorporation of an oro nasal mask (ONM) orother conveyance means in the breathing circuit. It is wellknown in the art to have such an ONM supported by a strap harnessand to have inlet and outlet valves, both for a breathable gassystem (WO82/02492) and for a filter system (EPO275934A2).However, problems may arise from a poorly fitting ONM whichallows outward leakage of exhaled gas with effective increase ofdead space. Also, moisture in the exhaled gas condenses on avisor, if fitted, to cause misting and impairment of vision. Inthe present invention a close fitting elasticated fabric helmetis used as a harness to exert even traction all round the rim ofthe ONM and pulls it onto the face to secure a good fit. Theneck seal of the hood, which forms an integral part of thebreathing apparatus, may be sealed by a draw string (W082/02492,EPO275934A2) but much inward leakage of the noxious externalatmosphere takes place past this type of seal. An elasticatedseptal neck seal (GB2129670A) allows less leakage but the leakagemay be further reduced by having a positive pressure inside thehood. A positive pressure may be achieved by passing exhaled gasto the hood space (GB2211098A, GB2164570A) but such designs aredefective because the moisture in the exhaled gas impairs vision.In EP-A-0 301 732 exhaled gas is passed into a chamber between a hood and an innerflexible membrane attached to the hood.Positive pressure breathing apparatus is well known (GB 1587121,GB 2074456A). In the present invention, unlike GB 1587121, areservoir is described between two hoods and it differs from GB2074456A in that complex pressure reducing valves are notrequired. In the present invention a positive pressure isachieved by passing dry gas under pressure and at constant flowdirectly into the hood space reservoir. There is virtually noinward leakage past the neck seal if the hood space remains atpositive pressure and this is ensured if the volume of thereservoir is in excess of the breathing volume of the wearer andif the inlet and outlet valves are set at appropriate openingpressures. In the present invention inward leakage past the ONMis not important and outward leakage fron ONM to hood space isminimised by improved goodness of fit. There is therefore nosignificant increase in effective dead space and misting isprevented by ingress of dry gas from the breathable gas source.Thus, the present invention discloses breathing apparatus havinga reservoir, in the hood space between inner and outer hoods,filled with dry breathable gas to prevent misting and underpositive pressure to prevent inward leakage; having the innerhood elasticated to support the conveyance means, to pull it ontothe face and to secure a good fit, and having an open circuit with one way valves to ensure that there is high performance withvery low dead space and high efficiency.

According to the present inventionbreathing apparatus to provide respiratoryprotection has an outer hood, an inner hood, a reservoirat positive pressure, a breathable gas source and a maskwith one way valves in a circuit system such that:

A) the outer hood is:

(i) made from impermeable gas proof material,

(ii) transparent at least in part,

(iii) completed by an elastic neck seal;

B) the inner hood is:

(i) close fitting to the head,

(ii) made from elasticated material,

(iii) attached to the outer hood,

(iv) attached to the rim of the conveyance means to support itand pull the rim onto the face;

C) the reservoir is:

(i) positioned in the space between the inner and outer hoods,

(ii) constructed with a volume which is in excess of thebreathing volume of the user;

D) the breathable gas source discharges dry breathable gasdirectly into the reservoir to raise it to positive pressure and

E) the mask covers the mouth and nose of the user andhas:

(i) a one way inlet valve which allows breathable gas to passfrom the reservoir to the cavity of the mask and

(ii) a one way outlet valve which allows breathable gas topass from the mask cavity to the ambient atmosphere.

Essential and preferred featuresof the component parts of the apparatus, inrelation to the atmosphere, are as follows.

(1) The outer protective hood is impervious to gas and resistantto flame to protect the head and respiratory tract of the wearer.

(2) The neck seal is made of elasticated material which fitsround the neck and, together with the outer hood, completes thegas impermeable enclosure.

(3) The central opening of the neck seal is stretched to passover the head when donning the hood and fits closely to the neckwhen donned.

(4) The conveyance means covers the nose and mouth.

(5) The cavity of the conveyance means is the space within it.

(6) The rim of the conveyance means seals against the face of thewearer.

(7) The inner hood is elasticated and tightly fitting to thehead. It is attached to the rim of the conveyance means, exertseven traction and pulls it onto the face to achieve a good seal.

(8) The reservoir is the space between the outer and inner hood.It has a volume which is greater than the breathing volume of thewearer and it contains breathable gas.

(9) The inlet valve allows gas to pass in only one direction fromthe reservoir to the cavity of the conveyance means.

(10) The outlet valve allows gas to pass in only one directionfrom the conveyance means cavity to the ambient atmosphere.

(11) The breathable gas source is a cylinder which contains thebreathable gas under pressure.

(12) The manual switch is used to switch on and off the supply ofbreathable gas from the source.

(13) The inner and outer hoods are joined together at thecircumference on the inner side of the outer hood.

(14) The opening of the inner hood is positioned at the front topermit vision and to make orientation obvious on donning.

(15) The external ambient atmosphere is outside the hood and maycontain smoke particles and noxious gases.

FIGURE

A specific embodiment and the functioning thereof is nowdescribed by way of example only with reference to theaccompanying schematic drawing in which figure 1 shows thebreathing apparatus as worn by a subject and having the componentparts numbered as above.

The breathing apparatus is donned by stretching theopening 3 oftheneck seal 2 and pulling theouter hood 1 over the head. Thisis attached 13 to theinner hood 7 which is therefore also pulledonto the head. The closely fittinginner hood 7 is also attachedto therim 6 of the conveyance means ormask 4 which iscorrectly positioned by the act of donning thehood 7 with theopening 14 at the front. Thebreathable gas source 11 isactivated manually by theswitch 12 and fills the reservoir 8with breathable gas under pressure. On inspiration, breathablegas is sucked in through the inlet valve 9 and the cavity 5 ofthemask 4 to the lungs. On expiration, exhaled gas passesthrough the cavity 5 of themask 4 and theoutlet valve 10 to theexternalambient atmosphere 15. Positive pressure in thereservoir 8 is maintained by an appropriate setting for theopening pressure of one or other or both of thevalves 9 and 10.

It is obvious to those skilled in the art that the outer hood maybe fire proof; the entire outer hood or only a part of it may betransparent; a draw string may be fitted round the neck; theconveyance means may be a mouth piece, oro nasal mask, full facemask; the inner hood may be elasticated in morethan one dimension; the inner hood attachment to the conveyancemeans rim may be direct or indirect and may be complete orincomplete; the conveyance means rim may be shaped to the faceand nose; the breathable gas may be air, oxygen or mixed gas,compressed or chemically generated; a reducing valve may berequired between the compressed gas cylinder and the reservoir; arelief valve may be required to prevent over pressurization ofthe reservoir; release of gas may be activated manually,automatically or on demand; there may be two eye openings with acentral part or cord to prevent deformation of the opening oropenings; there may be a plurality of inlet and outlet valves;the inner hood may support and carry the breathable gas sourceand container; an external or remote gas source may be added; thesystem may be adapted for closed or semiclosed circuit use; acarbon dioxide absorber and rebreathing reservoir may be addedand a filter or anti suffocation device may be added for use whenthe breathable gas source is exhausted. It is also obvious thatthe breathing apparatus has many applications in civilian useincluding escape from fire and smoke and toxic fumes in sewers,laboratories and chemical factories and in military use againstwar gases and other agents.

Claims (4)

1. Breathing apparatus to provide respiratory protection havingan outer hood (1), an inner hood (7), a reservoir (8) at positive pressure, abreathable gas source (11) and a mask (4) with one way valves (9, 10)in a circuit system such that:

   A) the outer hood is:

   (i) made from impermeable gas proof material,

   (ii) transparent at least in part,

   (iii) completed by an elastic neck seal;

   B) the inner hood is:

   (i) close fitting to the head,

   (ii) made from elasticated material,

   (iii) attached to the outer hood,

   (iv) attached to the rim of the mask to support itand pull the rim onto the face;

   C) the reservoir is:

   (i) positioned in the space between the inner and outer hoods,

   (ii) constructed with a volume which is in excess of thebreathing volume of the user;

   D) the breathable gas source discharges dry breathable gasdirectly into the reservoir to raise it to positive pressure and

   E) the mask covers the mouth of the user andhas:

   (i) a one way inlet valve (9) which allows breathable gas topass from the reservoir to the cavity of the mask,and

   (ii) a one way outlet valve (10) which allows breathable gas topass from the mask cavity to the ambientatmosphere.
2. Breathing apparatus according to claim 1 in which thebreathable gas source is compressed air.
3. Breathing apparatus according to claim 1 or 2 in which theopening pressures of the inlet and outlet valves are set tomaintain a positive pressure in the reservoir.
4. Breathing apparatus according to any preceding claim in whicha demand valve is provided.

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