[0001] This invention relates to a valve for use with breathing apparatus and to breathing
apparatus incorporating the valve. The valve according to the present invention is
capable of use as either an inhale valve or an exhale valve.
[0002] It is common practice in breathing apparatus to use simple flap valves as both inhale
valves and exhale valves. Such flap valves consist of a central stem carrying a flexible
essentially flat rubber disc which is capable of sealing against a surrounding surface
when the stem of the valve member is placed substantially centrally in an aperture
in the surface and an applied pressure difference directs the flexible disc towards
the surface. The rubber disc will flex away from the surface and permit gas flow through
the aperture when an opposite pressure difference exists across the disc. The rubber
disc may be formed with corrugations.
[0003] However such known flap valves are liable to open partially in the absence of a pressure
difference urging the disc into sealing contact with the surface surrounding the aperture.
This tendency gives rise to disadvantages when a flap valve is used as the external
inhale valve in breathing apparatus to be used in conditions where foreign matter
may come into contact with the inhale valve. This applies particularly in the medical
field where the breathing apparatus is liable to be contaminated by foreign matter
such as sweat, spit or vomitus, and the contaminant may enter through the aperture
into the valve mechanism or the interior of the breathing apparatus.
[0004] According to the present invention there is provided a valve for use with breathing
apparatus, the valve comprising a rigid circular disc having a solid central area
and a plurality of apertures between the solid central area and the circumference
of the disc, and a valve member which is an annular member of elastomeric material,
the valve member being secured over a circumferential edge of the disc such that the
annular valve member is under tension and, in the absence of a pressure difference
between opposite surfaces of the annular valve member tending to move the annular
valve member away from the disc, the annular valve member is maintained in a plane
covering the apertures in the disc.
[0005] The annular valve member may be maintained in contact with the solid central area
of the disc. Such contact may be obtained by providing an angularly projecting lip
on the free inner edge of the annular valve member or by so constructing the valve
that the tensioned annular valve member naturally engages the solid central area of
the disc.
[0006] Conveniently the circumferential edge of the disc is an outwardly projecting rim
on the disc and the valve member is formed with an integral peripheral flange defining
an inwardly facing channel, the valve member being secured to the disc by engagement
of the rim of the disc in the said inwardly facing channel. The outwardly projecting
rim of the disc may be displaced laterally relative to the solid central area of the
disc.
[0007] In one embodiment of the present invention which will be described the disc has a
peripheral flange which includes the rim and which has a circumferential recess of
which the rim forms a wall, the flange on the valve member engaging in the circumferential
recess.
[0008] Conveniently the apertures in the rigid disc are circular apertures the centres of
which are all at the same radial distance from the centre of the disc.
[0009] The valve member may be made of silicone rubber or other suitable resiliently flexible
material.
[0010] The present invention also comprehends breathing apparatus comprising means for supplying
breathing gas from a source thereof to a gas delivery means for delivering breathing
gas to a user, the means for supplying breathing gas including a demand valve for
passing breathing gas from the source in response to a reduction of pressure on inhalation
by the user, and an inhale valve located between the demand valve and the gas delivery
means, the inhale valve being a valve according to the present invention as recited
in the preceding paragraphs arranged such that the annular valve member moves away
from the disc in response to inhalation by the user.
[0011] In breathing apparatus in accordance with the present invention the demand valve
preferably includes a main valve and a pilot valve, the pilot valve comprising first
and second chambers separated by a pivotally mounted diaphragm, the first chamber
being connected to the inhale valve and the second chamber being connected to atmosphere,
a reduction in pressure in the first chamber at the commencement of inhalation causing
pivotal movement of the diaphragm to open a pilot jet communicating with the first
chamber with consequential opening of the main valve to pass breathing gas from an
outlet of the main valve over the solid central area of the disc on the opposite side
of the disc to that over which the annular valve member is tensioned, the breathing
gas also passing over an aperture defined by a cylindrical member, and the aperture
communicating with the first chamber whereby an increase in the rate of breathing
gas drawn through the inhale valve results in further pivoting movement of the diaphragm
thereby further opening the main valve and substantially preventing an increase in
the inhalation resistance of the demand valve as the rate of flow of breathing gas
through the demand valve increases.
[0012] In the embodiment of this aspect of the present invention which will be described
the breathing gas passes over a pair of apertures each defined by a cylindrical member
and each aperture communicating with the first chamber, and the cylindrical members
are located on either side of the outlet of the main valve.
[0013] The present invention will be further understood from the following detailed description
of preferred embodiments thereof which is made, by way of example, with reference
to the accompanying drawings, in which
Figure 1 shows in cross-section a first embodiment of a valve in accordance with the
present invention
Figure 2 shows in cross-section another embodiment of a valve in accordance with the
present invention
Figure 3 is a cross-sectional view through a demand valve incorporating an inhale
valve in accordance with the present invention,
Figure 4 is a cross-sectional view of the arrangement of Figure 3 taken along the
line IV-IV of Figure 3 and illustrating a means for maintaining an inhalation resistance
substantially independent of the rate of gas flow through the inhale valve, and
Figure 5 is a cross-sectional view, similar to Figure 4, of a modified form of valve
according to the present invention suitable for use in forcing breathing gas into
a patient's lungs.
[0014] In the drawings the same or similar parts are designated by like reference numerals.
[0015] Referring to Figure 1 of the accompanying drawings there is shown a valve comprising
a rigid circular disc 1 of a plastics material such as polysulphone or acetal. The
disc 1 has a solid central area 2 and, around the solid central area 2, a series of
circular apertures 3, 3 the centres of which are all at the same radial distance from
the centre of the disc. The disc 1 is formed with an outwardly extending rim 5 displaced
laterally relative to the solid central area 2 of the disc 1, the rim 5 being of lesser
thickness than the body of the disc which includes the solid central area 2. The disc
1 also includes a flange 6 which is substantially perpendicular to the plane of the
disc 1 and which extends from the disc 1 in the opposite direction to the direction
of lateral displacement of the rim 5.
[0016] The valve illustrated in Figure 1 further includes a valve member 7 consisting essentially
of a resiliently flexible annulus formed, for example, of silicone rubber. The inner
edge 10 of the annular valve member 7 defines an aperture of a smaller diameter than
the solid central area 2 of the disc 1.
[0017] Formed integrally with the annular valve member 7 is a flange 8 which defines an
inwardly facing channel 9. The annular valve member 7 is secured over the rim 5 which
is the circumferential edge of the disc 1 by engaging the rim 5 in the inwardly facing
channel 9 defined by the flange 8 of the annular valve member 7 so that the annular
valve member 7 is held in tension on the disc 1.
[0018] The tension in the annular valve member 7 results in the annular valve member 7 being
maintained in the planar position illustrated in Figure 1 in the absence of a significant
pressure difference between opposite surfaces of the annular valve member 7.
[0019] The rim 5 of the disc 1 may alternatively be arranged such that the surface of the
rim 5 over which the annular valve member 7 is tensioned is in the same plane as the
adjacent surface of the solid central area 2. The free inner edge 10 of the annular
valve member 7 will then contact the surface of the solid central area 2 of the disc
1.
[0020] An alternative embodiment of a valve in accordance with the present invention is
illustrated in Figure 2. The valve of Figure 2 differs from the valve of Figure 1
in the means of securing the annular valve member 7 to the disc 1 and in the provision
at the free inner edge of the annular valve member 7 of a continuous angularly projecting
lip 11 ensuring contact between the annular valve member 7 and the solid central area
2 of the disc 1 in the absence of a significant pressure difference across the annular
valve member 7.
[0021] The disc 1 illustrated in Figure 2 has its flange 6 formed with a circumferential
recess 12 adjacent the rim 5 so that the rim 5 constitutes a wall of the circumferential
recess 12. The flange 8 on the annular valve member 7 then engages over the rim 5
and into the recess 12, the projection on flange 8 being shaped to fit precisely into
the recess 12.
[0022] The valve of either Figure 1 or Figure 2 may advantageously be used as an inhale
valve in conjunction with a demand valve in breathing apparatus for supplying breathing
gas, for example oxygen, to a user such as a patient. Figures 3 and 4 show part of
one embodiment of breathing apparatus incorporating the valve of the present invention
with a pilot-operated demand valve.
[0023] Referring to Figures 3 and 4 of the accompanying drawings breathing gas from a suitable
source, for example a piped hospital gas supply, is fed to a channel 21 which is an
inlet channel of a main valve and which is terminated by a valve member which is a
resilient disc 22. The disc 22 has a small central aperture 23 through which gas passes
to a channel 24 and a pilot jet 25 which is normally closed by a pivotally mounted
diaphragm 26 which constitutes a partition separating a first chamber 27 from a second
chamber 28. The second chamber 28 is connected to atmosphere by an aperture 29 and
the diaphragm 26 is biased by springs (not shown) to keep the pilot jet 25 closed.
[0024] The main valve has an outlet 31 to which breathing gas is supplied from channel 21
via apertures 32 when the resilient disc 22 is caused to bow away from its valve seat
when the pilot jet 25 is opened.
[0025] An inhale valve essentially similar to the valve described with reference to Figure
1 is mounted adjacent the outlet 31 from the main valve so that breathing gas passing
through the main valve strikes the solid central area 2 of the disc 1 of the inhale
valve.
[0026] As shown more particularly in Figure 4 a pair of cylindrical members 35 and 36 define
apertures leading to the first chamber 27 . The cylindrical members 35 and 36 are
located on diametrically opposite sides of the outlet 31 from the main valve and the
cylindrical members 35 and 36 are situated so that the apertures defined thereby partially
overlap the solid central area 2 of the disc 1 of the inhale valve and are relatively
closely spaced from the solid central area 2.
[0027] The breathing apparatus illustrated in Figures 3 and 4 further includes a passage
38 leading to a mouthpiece or face mask used by a wearer such as a patient and further
includes an exhale valve 39 which is a flap valve constituted by an annulus located
in a recess 40 in the external surface of the wall which defines the passage 38.
[0028] In Figure 4 of the accompanying drawings the breathing apparatus is shown in the
inhale mode in the right half of the drawing and in the exhale mode in the left half
of the drawing.
[0029] In operation at the commencement of inhalation there is a reduction in pressure in
passage 38 which is communicated through the inhale valve to the first chamber 27
as a result of which the diaphragm 26 pivots about pivots 37 to open the pilot jet
25 thus permitting the resilient disc 22 to bow away from the valve seat 30 and allowing
breathing gas to flow from the channel 21 through the ports 32 and through the outlet
31. The breathing gas then strikes the solid central area 2 of the disc 1 of the inhale
valve and flows outwardly past the apertures defined by the cylindrical members 35
and 36, the outward flow being restrained by the flange 6 on the disc 1 and the chamber
defined thereby adjacent to the apertures 3, 3 etc. in the disc 1. The pressure difference
thus created across the annular valve member 7 causes the annular valve member 7 to
flex away from the disc 1 against the tension in the annular valve member 7 enabling
breathing gas to flow through the passage 38 for use as shown at 41 in Figure 4.
[0030] As the rate of flow of breathing gas past the apertures defined by the cylindrical
members 35 and 36 increases this gas flow will effect a further reduction in pressure
in the first chamber 27 by the Bernoulli effect. The diaphragm 26 is thus caused to
pivot further, enabling the resilient disc 22 to bow further and a greater volume
of breathing gas to pass through the main valve. The provision and location of the
apertures defined by the cylindrical members 35 and 36 and communicating with the
first chamber 27 of the pivot valve enable a substantial equalisation of resistance
to inhalation to occur over a wide range of gas flows to the patient or other user
of the breathing apparatus.
[0031] Exhale valve 39 remains closed throughout inhalation. However, when the patient or
other wearer of the breathing apparatus exhales, the annular valve member 7 resumes
its normal position closing apertures 3, 3, as shown on the left half of Figure 4,
and the exhale valve 39 opens permitting exhaled gases to pass freely to atmosphere.
[0032] If breathing apparatus in accordance with the present invention is to be used in
forcing breathing gas into a patient's lungs, for example in artificial respiration,
the construction of the apparatus should be such that, when the annular valve member
7 is flexed away from the disc 1 by the gas under pressure, the annular valve member
7 contacts a continuous surface and prevents escape of gas via the exhale valve 39.
[0033] This effect may be achieved by modifying the construction of the apparatus of Figure
4 to reduce the distance D between the upper end of the wall which defines passage
38 and the plane in which the annular valve member 7 is tensioned in the absence of
a pressure difference across it.
[0034] Alternatively the effect may be achieved as illustrated in Figure 5 of the accompanying
drawings by using, in order to define passage 38, a tube 42 which extends upwardly
well beyond the level at which the exhale valve 39 is mounted to the external surface
of the tube 42. When the annular valve member 7 is forced open under applied gas pressure,
as shown in the right-hand half of Figure 5, the annular valve member 7 contacts the
upper edge of tube 42 and prevents the applied gas from opening the exhale valve 39
with the result that all the applied breathing gas is forced into the patient's lungs.
[0035] The use of an inhale valve according to the present invention in breathing apparatus
such as that described with reference to Figures 3, 4 and 5 impedes any foreign matter
or contaminants from passing through the inhale valve into the apertures defined by
the cylindrical members 35, 36 and the interior mechanisms of the demand valve. The
presence of the cylindrical members 35, 36 is a further obstacle to contaminants entering
chamber 27 of the pilot valve.
[0036] Variations in the flow/inhalation resistance characteristic can be made by using
differently constructed discs 1 having different heights H for the flange 6 and using
different heights for the distance which the cylindrical members 35 and 36 extend
from the horizontal wall of the housing towards the disc 1.
[0037] Although the method of substantially equalising the resistance to inhalation over
a range of rates of gas flow has been described in connection with a particular breathing
apparatus, the method may be used in other breathing apparatus. The method may also
be used to produce another desired flow/inhalation resistance characteristic.
[0038] According to this aspect, therefore, the present invention also comprehends breathing
apparatus comprising means for supplying breathing gas from a source thereof to a
gas delivery means for delivering breathing gas to a user, the means for supplying
breathing gas including a demand valve and an inhale valve, the demand valve having
a chamber containing a diaphragm which is movable in response to a reduction of pressure
in the chamber on inhalation by the user for causing breathing gas to be passed from
the source through an outlet from the demand valve and thence through the inhale valve
to the user, the inhale valve having a solid central area and circumferential apertures
which are normally closed but which open to permit passage of inhale gas, the outlet
from the demand valve being located adjacent the solid central area of the inhale
valve so that gas flows over the solid central area substantially parallel thereto,
and at least one cylindrical member, which defines an aperture leading to the chamber
of the demand valve which contains the diaphragm, being located adjacent the gas flow
over the solid central area of the inhale valve whereby an increase in the rate of
breathing gas drawn through the inhale valve results in further movement of the diaphragm
to open the demand valve further and moderate any increase in the inhalation resistance
of the demand valve as the rate of flow of breathing gas through the demand valve
increases. The arrangement may be selected to prevent any substantial increase in
the inhalation resistance of the demand valve with increase in the rate of flow of
breathing gas.
[0039] The demand valve used in this aspect of the invention may be a simple demand valve,
or a pilot-operated demand valve. The only restriction on the type of demand valve
is that the demand valve must incorporate a diaphragm controlling movement of a valve
member such that the movement of the valve member to open the demand valve is generally
proportional to the movement of the diaphragm.
1. A valve for use with breathing apparatus, the valve comprising a rigid circular disc
having a solid central area and a plurality of apertures between the solid central
area and the circumference of the disc, and a valve member which is an annular member
of elastomeric material, the valve member being secured over a circumferential edge
of the disc such that the annular valve member is under tension and, in the absence
of a pressure difference between opposite surfaces of the annular valve member tending
to move the annular valve member away from the disc, the annular valve member is maintained
in a plane covering the apertures in the disc.
2. A valve according to Claim 1 wherein, in the absence of the said pressure difference,
the annular valve member is maintained in contact with the solid central area of the
disc.
3. A valve according to Claim 1 or Claim 2 wherein the circumferential edge of the disc
is an outwardly projecting rim and the valve member is formed with an integral peripheral
flange defining an inwardly facing channel, the valve member being secured to the
disc by engagement of the rim of the disc in the said inwardly facing channel.
4. A valve according to Claim 3 wherein the rim of the disc is displaced laterally relative
to the solid central area of the disc.
5. A valve according to Claim 3 or Claim 4 wherein the disc has a peripheral flange which
includes the rim and which has a circumferential recess of which the rim forms a wall,
the flange on the valve member engaging in the circumferential recess.
6. A valve according any one of the preceding Claims wherein the apertures in the rigid
disc are circular apertures the centres of which are all at the same radial distance
from the centre of the disc.
7. A valve according to any one of Claims 1 to 6 wherein the valve member is made of
silicone rubber.
8. Breathing apparatus comprising means for supplying breathing gas from a source thereof
to a gas delivery means for delivering breathing gas to a user, the means for supplying
breathing gas including a demand valve for passing breathing gas from the source in
response to a reduction of pressure on inhalation by the user, and an inhale valve
located between the demand valve and the gas delivery means, the inhale valve being
a valve according to any one of the preceding claims arranged such that the annular
valve member moves away from the disc in response to inhalation by the user.
9. Breathing apparatus according to Claim 8 wherein the demand valve includes a main
valve and a pilot valve, the pilot valve comprising first and second chambers separated
by a pivotally mounted diaphragm, the first chamber being connected to the inhale
valve and the second chamber being connected to atmosphere, a reduction in pressure
in the first chamber at the commencement of inhalation causing pivotal movement of
the diaphragm to open a pilot jet communicating with the first chamber with consequential
opening of the main valve to pass breathing gas from an outlet of the main valve over
the solid central area of the disc on the opposite side of the disc to that over which
the annular valve member is tensioned, the breathing gas also passing over an aperture
defined by a cylindrical member, and the aperture communicating with the first chamber
whereby an increase in the rate of breathing gas drawn through the inhale valve results
in further pivoting movement of the diaphragm thereby further opening the main valve
and substantially preventing an increase in the inhalation resistance of the demand
valve as the rate of flow of breathing gas through the demand valve increases.
10. Breathing apparatus according to Claim 9 wherein the breathing gas passes over a pair
of apertures each defined by a cylindrical member and each aperture communicating
with the first chamber, and the cylindrical members are located on either side of
the outlet of the main valve.
11. Breathing apparatus comprising means for supplying breathing gas from a source thereof
to a gas delivery means for delivering breathing gas to a user, the means for supplying
breathing gas including a demand valve and an inhale valve, the demand valve having
a chamber containing a diaphragm which is movable in response to a reduction of pressure
in the chamber on inhalation by the user for causing breathing gas to be passed from
the source through an outlet from the demand valve and thence through the inhale valve
to the user, the inhale valve having a solid central area and circumferential apertures
which are normally closed but which open to permit passage of inhale gas, the outlet
from the demand valve being located adjacent the solid central area of the inhale
valve so that gas flows over the solid central area substantially parallel thereto,
and at least one cylindrical member, which defines an aperture leading to the chamber
of the demand valve which contains the diaphragm, being located adjacent the gas flow
over the solid central area of the inhale valve whereby an increase in the rate of
breathing gas drawn through the inhale valve results in further movement of the diaphragm
to open the demand valve further and moderate any increase in the inhalation resistance
of the demand valve as the rate of flow of breathing gas through the demand valve
increases.
12. Breathing apparatus according to Claim 11 wherein the further movement of the diaphragm
to open the demand valve is selected to prevent any substantial increase in the inhalation
resistance of the demand valve with increase in the rate of flow of breathing gas.