Note: Descriptions are shown in the official language in which they were submitted.
~' W094/l9055 ~ t 3 4 ~ 6 9 PCT/GB92/0l656
BREAT~ING APPARATUS FOR RESPIRATORY PROTECTION
This invention relates to breathing apparatus for respiratory
protetion of ci~ilians and combatants.
Early types of breathing apparatus include a fl~xil~le hood }~lith
visor for aviators (F741127) and a rigid helmet with a glass
wi~dow for divers (GB42~96')s both with a remote breathable gas
supply. More recently, various types of portable breathing
apparatufi ha~e been described. A simple transp~rent l~as with ~
neck ~eal and a filter is }cnown (GB 2129670A) but the clesign is
defective due to a large e~ective dead space. The deficiency
may be DvercOme by incorporation of an oro nasal mask (ONM) or
other conveyance means in the bLeathing circuit. It i5 well
known in the art to have such an ONM supported by a strap harness
and to ha~e inlet and outlet ~alves, both for a ~reathable gas
~ystem (W082~02492) and for a filter system (EP0275g34A2).
Howe~er, problems may arise~rom ~ poorly fitting ONM which
allows outward leakage of exhaled gas with effectiv~ increase of
dead spaceO Also, moisture in the exhaled gas cond~nses on a
~i~or, if fitted, to cause misting and impairment of vision. In
the present invention a close ~itting elasticated f bric l~elmet
i8 used as a harness to exert even traction all rou~d the rim of
the ONM and pulls it onto the ~ce to secure a good ~it. The
neck seal of the hood9 which forms an integral part of the
:breathing apparatus, may be seale~ by a draw string (W082~024g2,
~P0275934~2) but much inward leakage of the noYious external
atmQsphere takes place pa~t this type of seal. An elasticated
septal neck seal ~GB2129670A) allows lefis leakage but the leakage
m~y be further reduced by having a positive pressur~ inside the
hood. A po~itive ~res~ure may be achieved by passing exhaled gas
to the hood space ~GB~211098A, GB21~4570A) but such lesigns are
defective because the moisture in the exhaled gas impairs vision.
Positive pressure breathing apparatus is well known (G~ 1587121
GB 2074456A). In the present invention, unli]ce GB lF.~71~1, a
reservoir iF~ described between two hoods and it di~fers ~rom GB
~07~56A in that co~plex pressure reducing valves ar~ not
req-lired. In the present in~ention a positive pressure i5
achie~ed by pasa~ng dry gas under pr~ssure and at con~tant flow
directly into the hood fipace reservoir. There is virtually no
inward leakage past the ne~k ~eal if the hood ~pace remains at
po~itive pressure and this is ensured i~ th~ ~olum~ of th~
reservoir is in excesfi of the breathin~ volume of the wearer and
if the inlet ~nd outlet v~lves are s~t at ~ppropri~te op~ning
presaures. In the pre~ent invention inward leakage past th~ ONM
i~ not important a~d outw~rd le~kag~ fron ONM to hood space is
minimi~d by improved goodness of fit~ There is therefore no .;
siqnific ~t increase in ef~ective de~d space and misting i5 ~-
prevented by ingress of dry gafi from the breathable gas ~ource. s
Thu~, th~ present invention discloses br~athing app~ratus h~ing
a res~rvoir, in the hood ~pace ~etween inner and outer hoods,
filled with dry breathable gas to pL-event misting and under ~.
positi~e pre~ure to pre~ent inw rd leakage; having thP inner
hood elasticated to support the conveyance meansl to pull it onto
the face and to se~ure a good fit, and having an open circuit
SUBSTITVTE Sl-IEET
W094/1905~ ~134nfi9 PCT/GB92/U1656
with one way valves to ensure that there is high performance with
very low dead space and high efficiency. The present invention is
~lled With a co-pending application which describ~s ~ ret~in~ng
harness means.
A~cordin~ to the present invention there is descri~ed by way
example only breathing apparatus to provide respiratory
protection and ha~ing an outer hood, an inner hood, a reservoir
at positive pressure, a breathable gas source and a conveyance
mean~ with one way va}ves in an open circuit system such th~t:
A~ the o~ter hood ls:
(i) made ~rom impermeable gas proof material,
~i$) transparent at least in part,
~ iii) completed by an elastic necX seal;
B) the inner hood is:
(1) close fitting to the head,
i~ ) made from elasticated material,
~iii) attached to the outer hood,
(iv~ attached to the rim of the convey~nce means to su~port it
and pull the rim onto the ~ce;
C) the reservoir i~: .
~i1 positioned in the space between the inner ~nd outer hoods,
~ii) con~tructed with a volume which is in excess of the
breathing ~olume of the user;
D) the breathable gas:source discharges dry breathable gas
direatly into the reseL-voir to raise it to positiv~ pr~ssure .~nd
E) the conveyance means covers the mouth and nose of the user and
has~
~ i) a one way inlet valve which allows breathable ~s to pass
from the reservoir to the cavity of th~ conveyance means and
~ a one way o~t~let valve which allows breathable gas to
pa~ rom the conveyance mean~ c~vity to ~hq ambient atmo phere.
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~lB~TI Z U IF SHEE ~
~' I
~ ~ - W094/l9055 213 ~ o ~ g PCTIGB9Z/0l656
A
The functions of the component parts of the ~pparatus, in
relation to the atmosphere, are as follows.
(l) The outer protective hoo~ is impervious to gas and resistant
to flame to protect the head and respiratory tract of the we~rer.
~2) The neck ~eal i~ made of elasticated material which fit~ }
round the neck and, together with the outer hood, completes the i~
ga~ impermeable enclosure.
~3) The central opening of the neck seal is stretched to pass
over the head when donning the hood and ~its closely tG the neck
when donne~. -
(4) The conveyance means covers the nose and mouth.
~5) The cavity of the conveyance means i5 the space within it.
~6~ The rim o~ the con~eyance means se~ls against the ~ace o~ the
wearer.
(7) The inner hood is elastic~ted and tightly fitting to the
head. It is attached to the rim of the conveyance means, exerts
e~en traction and pulls it onto the ~ace to achieve a good s~al.
~) $he reservoir is the space between the outer and inner hood.
It has a ~olume which is greater than tl~e breathing volume o~ tl-e
wearer and it contain~ breathable gas.
~9) The inlet valve allows gas to pass in only one direction ~rom
the reser~oir to the cavity of the conveyance means.
~10) The outlet val~e allows gas to pass in only one direction
from the conveyance meanfi cavity to the ambient atmosphere.
~11) The breathable gas source i5 a cylinder which contains the
breathable ga~ under pressure~
2) ~he manual switch is used to s~itch on and o~ the supply o~
breathable gas from the source.
~13) The inner and outer hoods are joined t~gether at the
circum~erence on the inner side of the outer hood.
~14) The opening of the inner hood is positioned at the ~rGnt to
permit vi~ion and to ma~e orientation obviGus on donnin~.
(15) The external am~ient atmosphere is outside the hood and may
contain smoke particles and noxious gases.
: :
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SUBSTITUTE SHEE~
WO94/l9055 PCT/GB92/016~6
2i3~069 ,1,
FIGURE
A speclfic embodiment and the functioning thereof i5 nowdescr~bed by way of example only with reference to the
accompanying schematic drawing in which fig~re 1 sl~ows the
breathing apparatus as worn by a sub~ect and having the component
parts numbered as above.
The breathing apparatus is donned ~y stretching the opening 3 o~
the neck seal 2 and pullin~ the outer hood 1 over the head. This
is attached 13 tc the inner hood 7 which is theLe~ore also ~Julle~l
onto the head. The closely fitting inner hood , is also ~IttaCl'leC
to the rim ~ of the con~ey~nc~ m~ans OL- n~sk ~ h i5
corr~ctly positioned by the act of ~lonning the hoc~d 7 with the
opening 14 at the front. The breathable gas source 11 is
activated manually by the switch I2 and fills the reservoir 8
with breathable gas under pressure. On inspir~tion, ~reath~ble
gas is sucked in through the inlet valve g and the C~Yity 5 of
the mask 4 to the lungs. On ~xpiration, e~haled g~s passes
through the cavity 5 of the mask 4 and ~he outlet valve 10 to the
external ambient atmosphere 15. Positi~e pressure in the
reservoir 8 is maintained by an appropriate settin~ for thr
ope~lng pressure of one or other or both of tl-e ~a1~JeS ~ and 10.
It is obvious to those skilled in the art that th~ out~r hood may
be fire proof; the entire outer hood or only p~rt of it may l~e
transparent; a draw string may be fitted round the necl:; the
con~eyance mean5 m~y be a mouth piece, oro nasal mask, ~ull f~c~
mask or other device; the inner hood may be elasticatf~d in more
than one dimension; the inner hoo~ atta~hn~ent to tl~ c..n:e~
means rim may be direct or indirf-ct ~ncl may he coll~lete or
incomplete; the conveyance me~ns rirn may be shlped ~:, th~ ce
and nose; the breathable gas may be air, o~yg~n or mi~cl f~as
compressed or fhemically generate~; a reducing v~lve n~.~y l~e
re~uired between the compressed gas cylinder and the reser~oir; .
relief valve may ~e required to prevent o~rer p7 ~ssuLir~ation rJf
the reservoir; release of gas may be activat~cl m~nually,
automatically or on d~mand; th~re may l~e twl~ eye op~nin~s wi th
central part or cord to prevent deformation o~ the opening or
openingfi; there may be a plur~}ity of inlet ~n~ <:utlet ~ al.~.?s;
the inner hood may support and carry the breathahle ~as s ourc~
and c:ontainer; an external or remote gas soux.-e may be added; the
~ystem may be adapt~d for clo~ed or semiclos~d ci~-cuit use; a
carbon dioxide absorb-~r and rebre~thing reser~roir may be ~dded
and a filter or anti suffocation device may be added for us~ wh~n
the breathable gas source is exhausted. It is also ob-~ious that
t)~e breathing apparatus has many applications in civilian us~
inaluding escape from fire and smoke ~nd toxic ~um~s in ~ew~rs, ~-
laboratories and chemical factories ancl in military u5e ~gainst
w~r gafies and oth~r agentsO
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