BREATHING APPARATUS FOR RESPIRATORY PROTECTION

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: BREATHING APPARATUS FOR RESPIRATORY PROTECTION Thiε invention relates to breathing apparatus for respiratory protetion of civilians and combatants. Early types of breathing apparatus include a flexible hood with a visor for aviators (P741127) and a rigid helmet with a glass window for divers (GB426962) , both with a remote breathable gas supply. More recently, various types of portable breathing apparatus have been described. A simple transparent bag with a neck seal and a filter is known (GB 2129670A) but the design is defective due to a large effective dead space. The deficiency may be overcome by incorporation of an oro nasal mask (ONM) or other conveyance means in the breathing circuit. It is well known in the art to have such an ONM supported by a strap harness and to have inlet and outlet valveε, both for a breathable gas system ( O82/02492) and for a filter system (EP0275934A2) . However, problems may arise from a poorly fitting ONM which allows outward leakage of exhaled gas with effective increase of dead space. Also, moisture in the exhaled gas condenses on a visor, if fitted, to cause misting and impairment of vision. In the present invention a close fitting elasticated fabric helmet is uεed aε a harness to exert even traction all round the rim of the ONM and pulls it onto the face to secure a good fit. The neck seal of the hood, which forms an integral part of the breathing apparatus, may be sealed by a draw string ( 082/02492, EP0275934A2) but much inward leakage of the noxious external atmosphere takes place past this type of seal. An elasticated εeptal neck seal (GB2129670A) allows less leakage but the leakage may be further reduced by having a positive pressure inside the hood. A poεitive pressure may be achieved by passing exhaled gas to the hood space (GB2211098A, GB2164570A) but such designs are defective because the moisture in the exhaled gas impairs vision. Positive pressure breathing apparatus is well known (GB 1587121, GB 2074456A) . In the present invention, unlike GB 1587121, a reservoir iε described between two hoods and it differs from GB 2074456A in that complex pressure reducing valves are not required. In the present invention a positive pressure is achieved by pasεing dry gas under pressure and at constant flow directly into the hood space reservoir. There is virtually no inwar * d leakage past the neck seal if the hood space remains at positive pressure and this iε ensured if the volume of the reservoir is in excesε of the breathing volume of the wearer and if the inlet and outlet valves are set at appropriate opening presεureε. In the preεent invention inward leakage past the ONM is not important and outward leakage fron ONM to hood space is minimised by improved goodness of fit. There is therefore no significant increase in effective dead space and misting is prevented by ingress of dry gas from the breathable gas source. Thus, the present invention discloses breathing apparatus having a reεervoir, in the hood space between inner and outer hoods, filled with dry breathable gas to prevent misting and under poεitive presεure to prevent inward leakage; having the inner hood elasticated to support the conveyance means, to pull it onto the face and to secure a good fit, and having an open circuit 1 SUB S TITUTE SHEET with one way valves to ensure that there is high performance with very low dead space and high efficiency. The present invention is filed with a co-pending application which describes a retaining harness means. According to the present invention there is described by way of example only breathing apparatus to provide respiratory protection and having an outer hood, an inner hood, a reservoir at positive pressure, a breathable gas εource and a conveyance meanε with one way valves in an open 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 it and 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 the breathing volume of the user; D) the breathable gas εourσe discharges dry breathable gas directly into the reservoir to raise it to poεitive pressure and E) the conveyance means covers the mouth and nose of the uεer and has: (i) a one way inlet valve which allows breathable gas to pasε from the reεervoir to the cavity of the conveyance means and (ii) a one way outlet valve which allows breathable gas to paεε from the conveyance means cavity to the ambient atmosphere. T The functions of the component parts of the apparatus, in relation to the atmosphere, are as follows. (1) The outer protective hood is impervious to gas and resistant to flame to protect the head and respiratory tract of the wearer. (2) The neck seal iε made of elasticated material which fits round the neck and, together with the outer hood, completes the gas impermeable enclosure. (3) The central opening of the neck seal is stretched to pass over the head when donning the hood and fits closely to the neck when 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 sealε against the face of the wearer. (7) The inner hood is elasticated and tightly fitting to the head. It is attached to the rim of the conveyance means, exerts even traction and pulls it onto the face to achieve a good seal. (8) The reservoir iε the εpace between the outer and inner hood. It has a volume which is greater than the breathing volume of the wearer and it contains breathable gas. (9) The inlet valve allows gas to pass in only one direction from the reservoir to the cavity of the conveyance means. (10) The outlet valve allows gas to pass in only one direction from the conveyance means cavity to the ambient atmosphere. (11) The breathable gas source is a cylinder which contains the breathable gas under preεεure. (12) The manual switch is uεed to εwitch on and off the εupply of breathable gas from the source. (13) The inner and outer hoods are joined together at the circumference on the inner side of the outer hood. (14) The opening of the inner hood is positioned at the front to permit vision and to make orientation obvious on donning. (15) The external ambient atmosphere is outside the hood and may contain smoke particles and noxious gaεeε. FIGURE A specific embodiment and the functioning thereof is now described by way of example only with reference to the accompanying schematic drawing in which figure 1 shows the breathing apparatus as worn by a subject and having the component parts numbered as above. The breathing apparatus is donned by stretching the opening 3 of the neck seal 2 and pulling the outer hood 1 over the head. This is attached 13 to the inner hood 7 which is therefore also pulled onto the head. The closely fitting inner hood 7 is also attached to the rim 6 of the conveyance means or mask 4 which is correctly positioned by the act of donning the hood 7 with the opening 14 at the front. The breathable gas source 11 is activated manually by the switch 12 and fills the reservoir 8 with breathable gas under pressure. On inspiration, breathable gas is sucked in through the inlet valve 9 and the cavity 5 of the mask 4 to the lungs. On expiration, exhaled gas passes through the cavity 5 of the mask 4 and the outlet valve 10 to the external ambient atmosphere 15. Positive pressure in the reservoir 8 is maintained by an appropriate setting for the opening presεure of one or other or both of the valves 9 and 10. It is obvious to those skilled in the art that the outer hood may be fire proof; the entire outer hood or only a part of it may be transparent; a draw string may be fitted round the neck; the conveyance means may be a mouth piece, oro nasal mask, full face mask or other device; the inner hood may be elasticated in more than one dimension; the inner hood attachment to the conveyance meanε rim may be direct or indirect and may be complete or incomplete; the conveyance means rim may be shaped to the face and nose; the breathable gas may be air, oxygen or mixed qas, compressed or chemically generated; a reducing valve may be required between the compressed gas cylinder and the reεervoir; a relief valve may be required to prevent over pressurization of the reεervoir; release of gas may be activated manually, automatically or on demand; there may be two eye openings with a central part or cord to prevent deformation of the opening or openingε; there may be a plurality of inlet and outlet valves; the inner hood may εupport and carry the breathable gas source and container; an external or remote gas source may be added; the εyεtem may be adapted for cloεed or εemiclosed circuit uεe; a carbon dioxide absorber and rebreathing reservoir may be added and a filter or anti suffocation device may be added for use when the breathable gas source is exhausted. It is also obvious that the breathing apparatus has many applications in civilian use including escape from fire and smoke and toxic fumes in sewers, laboratories and chemical factories and in military use against war gaseε and other agentε. SUB S TITUTE SHEET

Claims: CLAIMS 1) Breathing apparatuε to provide respiratory protection having an outer hood, an inner hood, a reservoir at positive pressure, a breathable gaε εource and a conveyance means with one way valveε in an open 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 it and 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 iε in excess of the breathing volume of the user; D) the breathable gas source diεchargeε dry breathable gas directly into the reεervoir to raiεe it to positive pressure and E) the conveyance meanε coverε the mouth and noεe of the uεer and haε: (i) a one way inlet valve which allows breathable gaε to paεs from the reservoir to the cavity of the conveyance meanε, and (ii) a one way outlet valve which allows breathable gas to paεs from the conveyance meanε cavity to the ambient atmosphere. 2) Breathing apparatuε according to claim 1 in which the breathable gaε εource iε compreεεed air. 3) Breathing apparatuε according to claim 1 or 2 in which the opening preεεureε of the inlet and outlet valveε are εet to maintain a poεitive preεεure in the reservoir. 4) Breathing apparatus according to any preceding claim in which a demand valve is provided. 5) Breathing apparatuε substantially aε herein described according to the drawing. SUBSTITUTE SHEET

Inventors: RICHARDS BRIAN JOHN, STEWART JOHN STEWART SIMPSON, RICHARDS, BRIAN, JOHN, STEWART, JOHN, STEWART, SIMPSON
Applicants: RICHARDS BRIAN J, STEWART JOHN STEWART SIMPSON, RICHARDS, BRIAN, JOHN, STEWART, JOHN, STEWART, SIMPSON
Application year: 1992
Main classification: A62B17
IPC codes: A62B17