Note: Descriptions are shown in the official language in which they were submitted.
CA 02226099 1997-12-31
W O 97/02070 PCT/SE~
A BR~aT~ING EOUIPME3NT
The present invention relates to breathing equipment o~ the
kind which includes a breathing mask, a breathing hood or the~~ 5 like, and conduit means for delivering breathing gas to the
mask or hood.
By mask is meant here both full face masks that are provided
with a viewing visor, and so-called half masks which cover
only the nose and mouth of the wearer. Masks o~ this kind are
used together with many different types o~ breathing appara-
tus used by firemen, military personnel and industrial
personnel working in toxic environments, for instance. The
term breathing hood includes, among other things, so-called
evacuation or escape hoods which are used temporarily when
evacuating a building or a locality filled with smoke or some
other gas, possibly toxic gas, for instance.
A common ~eature of these devices is that breathing gas is
supplied to the space delimited by the mask or hood. If a
fault should occur so that the supply of breathing gas ceases
or becomes insufficient, for instance as a result of a
mechanical fault in the equipment or because the supply of
breathing gas has been exhausted, no fresh gas will be
supplied to the wearer o~ the equipment. As a result, the
carbon dioxide content of the available breathing air will
build-up while the oxygen content diminishes at the same
time, which can quickly lead to suffocation.
It has been proposed to provide breathing equipment of this
kind with alarm means which functions to warn the wearer that
the concentration of harmful substances in the breathing air
is approaching a critical level. When an alarm is activated,
the wearer must quickly remove the mask or hood and take him-
sel~/herself to a sa~e area.
CA 02226099 1997-12-31
W O 97/02070 PCT/SE~GI'~5~
Thus, this requires the wearer to be fully instructed
beforehand of the measures and procedures that should be
taken when an alarm is activated, for instance. It is very
likely that a person wearing a so-called evacuation or escape
hood will not have sufficient knowledge of recommended pro-
cedures or the presence of mind to handle such an emergency
correctly. It is also possible that the wearer has been
rendered unconscious or is close to unconsciousness prior to
an alarm signal being given, therewith rendering the person
incapable of taking any safety measures at all.
The main object of the present invention is to provide
breathing equipment of the aforesaid kind which in the event
of a malfunction in the breathing gas supply will automati-
cally open a connection between the interior of the mask orhood and the surrounding atmosphere so as to enable this
atmosphere to be breathed by the wearer of the mask or hood.
This object is achieved with breathing equipment of the kind
which is defined in the first paragraph and which is charac-
terized in accordance with the invention by a valve means
which is normally closed in use and which when open connects
the space delimitated by the mask or by the hood with the
surrounding atmosphere, therewith to enable this atmosphere
to be breathed, and by means for detecting when the supply
of breathing gas to the mask or hood has fallen beneath a
given level and for opening the valve means in accordance
therewith.
When wearing breathing equipment o~ this kind, the wearer
will always be able to breathe the surrounding atmosphere in
the event of a malfunctioning of the breathing gas supply
without needing to do anything himself/hersel~, This min;m;z -
es the risk o~ the wearer suffocating.
It is preferred that the valve means is a pressure-controlled
valve adapted to open when the pressure in the breathing gas
CA 02226099 1997-12-31
W O 97/02070 PCT/SE9GI'~
conduit has fallen beneath a predetermined value. In this
regard, the valve means may conveniently include a spring-
biassed valve body which is pressed sealingly against a valve
seat when the conduit pressure exceeds said value, but which
is moved away from the seat by spring force when the pressure
falls beneath said value.
This provides an automatic valve function without the need
of additional control and manoeuvering means.
In one preferred embodiment of the invention, the valve body
has the form of a spring-loaded valve plate which is actuated
directly by the pressure of the breathing gas. The plate is
disposed in a housing which is intended to be fitted over an
opening in the mask or hood and which includes a chamber that
communicates with the breathing gas conduit and whose one
wall is comprised either completely or partially of said
plate, which closes the opening when the pressure prevailing
in the chamber is sufficient to this end. Passageways are
provided which connect the interior of the mask or hood with
the surrounding atmosphere when the plate is moved away from
the opening.
Other features of the invention will be apparent from the
following Claims.
The invention will now be described in more detail with
reference to an exemplifying embodiment thereof and also with
reference to the accompanying drawing, in which
Fig. 1 is a schematic illustration of a so-called escape hood
~ supplemented with an inventive arrangement; and
l Fig. 2 illustrates schematically an exemplifying embodiment
of the inventive arrangement.
CA 02226099 1997-12-31
W O 97/02070 PCT/~',5'~ 2
Fig. 1 illustrates a so-called escape hood 1 which is con-
nected to a breathing gas container (not shown) by means of
a conduit 2. A hood of this kind can be used temporarily, for
instance, to protect against smoke and gases in an emergency,
for instance in the case of fire, gas leakages from gas
pipes, or in toxic gas environments created by chemicals.
As breathing gas flows through the conduit, a throttle means
14 in the conduit 2 generates an overpressure therein. In the
case of the illustrated embodiment, a valve means 4 is
connected so as to be actuated by the gas pressure in the
conduit 2.
When the system functions normally, the wearer breathes gas
flowing from the conduit 2 into the hood 1 via an inlet 3.
Exhalation air leaves the hood 1 through an exhalation valve
5 or simply as a result of leakage locations between the hood
and the wearer's neck.
When all of the gas carried in the container connected to the
conduit 2 has been consumed or when the gas supply falls off
for some other reason, the situation is sensed by the valve
means 4 which therewith opens a connection between an opening
6 in the hood 1 and the surrounding atmosphere, via at least
one combined outlet and inlet 7.
Thus, the wearer is able to breathe the surrounding atmo-
sphere when the supply of breathing gas ceases or has fallen
to beneath a given value. This is a better alternative than
breathing the exhalation air under any circumstance. Inhala-
tion of exhalation air would quickly result in suffocation.
The danger of the surrounding atmosphere being immediately
fatal is very small in many cases.
Fig. 2 illustrates an embodiment of an inventive valve means
in more detail, wherein those components that find correspon-
CA 02226099 1997-12-31
W O 97/02070 PCTI~ 7
dence in Fig. 1 have been identified by the same reference
signs.
Reference numeral 1 thus identifies part of the wall of a
J 5 hood shown in Fig. 1. The wall has provided therein an
opening 6 which is held closed by a valve plate 8 in normal
use conditions. The plate 8 forms one wall of a chamber 9 in
a housing 10 mounted on the hood 1. The chamber g communi-
cates with the breathing gas supply conduit 2, so that the
pressure in the conduit 2 will act directly on the plate 8
and a diaphragm 12. When gas flows to the wearer, the
pressure in the conduit 2 may correspond to an overpressure
of about 0.1-0.2 bar for instance, which is sufficient to
hold the valve plate 8 in sealing abutment with the defining
edges of the opening 6. If the pressure in the conduit 2
falls beneath a predetermined value, the valve plate 8 will
be moved away from the edges of the opening 6 in response to
the force exerted by a pressure spring 11 mounted around the
opening. This movement of the plate 8 is enabled by a
flexible diaphragm 12 of the so-called roll diaphragm type
fitted to the housing lo.
When the plate 8 is in an open position, shown in broken
lines, the interior of the hood 1 communicates with the
surrounding atmosphere through openings 13 in the housing 10,
these openings corresponding to the outlet and inlet 7 shown
in Fig. 1. The wearer is then able to breath the surrounding
atmosphere freely. If desired, the openings 13 may, of
course, be provided with suitable filter means.
The valve means can be constructed to open at a desired
pressure level in the conduit 2, by appropriate choice of the
area of the valve plate 8 and the force of the spring 11.
i
In addition to finding use in a breathing hood 1, the
inventive arrangement can also be used in a full face mask
or a so-called half mask. The illustrated and described
CA 02226099 1997-12-31
W O 97/02070 PCT/SE~
embodiment has been chosen merely to describe the principle
of the invention in a simple manner. The design and attach-
ment of the arrangement can be varied as desired within the
scope of the Claims. For instance, the conduit 2 can be
connected to the chamber 9 so that all breathing gas will
pass through the chamber before being delivered to the hood
or mask. The design of the valve means can also be varied in
several respects while maintaining its function of control-
ling the supply of breathing gas, such that the valve will
automatically open the connection between the interior of the
hood or the mask and the surrounding atmosphere when necess-
ary, without requiring the wearer to perform any action in
this regard, which is a central characteristic feature of the
inventive arrangement.
In addition to being placed on the outside of a breathing
hood or mask, the inventive valve means may alternatively be
mounted on the inside of the hood or mask and comprise an
inwardly opening valve body. The pressure spring may, of
course, be replaced with a pull spring when wishing to place
the spring on the other side of the plate 8, for instance.
In addition to sensing the pressure in the conduit 2, it is
also possible to use means which sense the flow of breathing
gas and to initiate automatic opening of the valve means when
the rate of flow is low or non-existent.
