LUNG DEMAND REGULATOR

There is disclosed a lung demand regulator for a breathing apparatus comprising: a flow regulation mechanism having a closed configuration; a connection mechanism for releasably connecting the lung demand regulator to a face mask; and a lockout mechanism for locking the flow regulation mechanism in the closed configuration, the lockout mechanism configured to be activated by at least one release element, the movement of the at least one release element being translated to the lockout mechanism via a cam element and cam follower arrangement. Also disclosed is a face mask comprising a lung demand regulator and a breathing apparatus comprising a lung demand regulator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Application No. 22216092.1, filed on Dec. 22, 2022, the entire contents of which being fully incorporated herein by reference.

This disclosure relates to lung demand regulators for breathing apparatus and, more specifically to lung demand regulators for self-contained breathing apparatus.

BACKGROUND OF THE INVENTION

Breathing apparatus commonly comprises a lung demand regulator, which may also be known as a second-stage regulator. The lung demand regulator is configured to deliver breathing gas to the user at a suitable pressure for breathing. Lung demand regulators may be configured to permit a constant low flow of gas during use in order to maintain positive pressure in the breathing mask, thereby preventing ingress of the ambient gas into the mask. In order to conserve breathing gas, the user may need to disable the breathing gas flow when not required, such as when removing the mask. The additional user intervention required in known lung demand regulators can be problematic as users may forget to disable the breathing gas flow.

Therefore, it should be understood that it is desirable to provide improvements to demand regulators in relation to the conservation of breathing gas.

SUMMARY OF THE INVENTION

According to a first aspect, there is provided a lung demand regulator for a breathing apparatus. The lung demand regulator may comprise a flow regulation mechanism for regulating a flow of breathing gas, the flow regulation mechanism having a closed configuration in which breathing gas flow can be substantially prevented. The lung demand regulator further comprises a connection mechanism for releasably connecting the lung demand regulator to a face mask and the connection mechanism comprises at least one moveable release element configured to be manually actuated by a user to release the connection mechanism. The lung demand regulator further comprises a lockout mechanism for locking the flow regulation mechanism in the closed configuration. The lockout mechanism is configured to be activated by the at least one release element. The lockout mechanism comprises a lockout actuator configured to activate the lockout mechanism. The at least one release element comprises a cam element and the lockout actuator comprises a cam follower configured to engage with the cam element, such that the lockout actuator is actuated by movement of the at least one release element.

The lung demand regulator may be intended for use with a self-contained breathing apparatus (SCBA), but it should be understood that the lung demand regulator may also have applications in other types of breathing apparatus, such as self-contained underwater breathing apparatus (SCUBA) and emergency escape breathing apparatus.

The flow regulation mechanism may be movable from a substantially closed position to a substantially open position or be movable to any point between the closed and opened positions.

The lockout mechanism may comprise one or more levers configured to be pivotable which may communicate a force from the at least one release element to the flow regulation mechanism.

The cam element and cam follower may be made from the same or different materials. The same or different materials may have a suitably low coefficient of friction to ensure the cam element and cam follower can slide past each other with suitably low resistance. The same or different materials may also be suitably resistant to repeated abrasive contact.

The at least one release element may be movable in a substantially radial direction relative to a longitudinal axis of an outlet port of the flow regulation mechanism.

The at least one release element may, for example, be a button on the outside of the lung demand regulator. The at least one release element may be operated by the user pressing the at least one release element inwards radially towards the longitudinal axis.

The at least one release element may be biased so as to return to its inactive position once the user releases the at least one release element. If configured to be biased, the at least one release element may provide a suitably resistive force to the user to reduce the likelihood of accidental actuation by the user.

The substantially radial movement of the at least one release element may be translated into a movement of the lockout actuator in a direction substantially parallel to the longitudinal axis by the cam element and cam follower.

The cam element may be configured with a first chamfered face. The cam follower may be configured with a second chamfered face. The planes of the first chamfered face and second chamfered face may be substantially parallel to each other.

It should be understood that the cam element with a first chamfered face which, as a result of being driven towards the cam follower, which is optionally also configured with a second chamfered face, may cause the cam follower to move up along the first chamfered face. The cam follower may be suitably constrained to move along only one axis.

The first chamfered face may be configured with an angle substantially complementary to the angle of the second chamfered face so as to optimise the translation of force between the cam element and cam follower. The planes of the first chamfered face and second chamfered face may be substantially parallel.

The lung demand regulator may comprise two cam elements arranged to act in substantially opposing directions against the cam follower. Each cam element may be provided on a respective release element. The release elements may be actuatable in opposing directions. The release elements may be arranged on opposing sides of the lung demand regulator.

The lockout mechanism may comprise a lockout lever configured to be pivotable about a first pivot.

The lockout actuator may be configured to interface with the lockout lever such that movement of the lockout actuator pivots the lockout lever about the first pivot.

The lockout lever may be made from a material of sufficient rigidity to resist deformation during use. It should be understood that the lockout lever may also have a cross section configured to further increase the relative rigidity of the lockout lever, such as T-shaped, I-shaped, or U-shaped cross sections.

It should be understood that the lockout actuator may be configured to include a sealing element to substantially isolate the internal atmosphere from the ambient atmosphere, while still permitting the lockout actuator to be movable. The sealing element may comprise a groove around the outside of the lockout actuator and an O-ring partially inside the groove. The lockout actuator may be configured as a piston-like element, slidably moveable in a bore of the lung demand regulator.

The lung demand regulator may comprise a flow regulation lever configured to be pivotable about a further pivot.

The flow regulation lever may be configured to actuate the flow regulation mechanism. The flow regulation lever may be configured to contact a diaphragm of the lung demand regulator so as to be pivoted about the further pivot by movement of the diaphragm. The flow regulation lever may be configured to be locked by the lockout mechanism in a locking position in which the flow regulation mechanism is configured in the closed configuration.

The flow regulation lever may comprise a foot which contacts the diaphragm, causing the flow regulation lever to pivot about the further pivot as the diaphragm moves.

The lockout mechanism may further comprise a diaphragm retention lever configured to be pivotable about a second pivot. The diaphragm retention lever may be configured to contact the diaphragm and retain it in a position in which the flow regulation lever maintains the flow regulation mechanism in the closed position.

The lockout lever may be configured to interface with the diaphragm retention lever such that the pivoting movement of the lockout lever pivots the diaphragm retention lever about the second pivot.

The lockout actuator may be configured to interface with the lockout lever at a first position on the lockout lever at a first distance from the first pivot, and the lockout lever may be configured to interface with the diaphragm retention lever at a second position on the lockout lever at a second distance from the first pivot, wherein the second distance is greater than the first distance.

This configuration may compound a relatively small movement of the at least one release element into larger movements of the lockout lever and the diaphragm retention lever, so as to provide sufficient travel to move the diaphragm retention lever into the locking position. This compound lever arrangement may also reduce a force applied by the at least one release element to the lockout actuator to reduce the likelihood of damage occurring to the diaphragm or other components.

The lockout lever of the lung demand regulator may further comprise a stop element configured to prevent over-rotation of the lockout lever by contacting a section of the lung demand regulator body. The stop element may be positioned on the substantially opposite side of the first pivot to the main length of the lockout lever. It should be understood that the prevention of over-rotation of the lockout lever may prevent over rotation of the flow regulation mechanism. Undue tension on the diaphragm caused by possible over rotation of the flow regulation mechanism may also be substantially prevented.

The lockout mechanism may further comprise a locking element configured to hold the diaphragm retention lever in a fixed position corresponding to the closed configuration. The locking element may comprise a spring element. The force required to overcome the holding force of the locking element may be substantially equivalent to the force generated against the diaphragm retention lever by the diaphragm when the user inhales. Hence, the user may be able to deactivate the lockout mechanism by inhaling. The locking element may additionally or alternatively comprise a detent.

It should be understood that any pivots about which a component of the lung demand regulator may be configured to pivot may take any form, for example pivot joint, ball and socket joint, hinge joint, or plastic hinge.

The at least one release element may comprise a first keying element. It should be understood that the first keying element may be made from a material of sufficient rigidity to resist deformation during use.

The first keying element may comprise one or more protrusions and one or more depressions which are configured to complement a complementary second keying element on a face mask to which the lung demand regulator may be connected, enabling the lung demand regulator to latch or lock on to the face mask.

The first keying element may be configured to interface with a substantially annular second keying element on the face mask. It should be understood that the second keying element may comprise a cut-out of a substantially similar shape to the to the first keying element so to enable the first keying element to fit within the second keying element.

The first keying element and the second keying element may be configured to permit rotation of the lung demand regulator about the longitudinal axis relative to the face mask.

It should be understood that a profile cut-out substantially similar in shape to the first keying element, revolved around an axis to form a continuous annulus of the second keying element, may permit the first keying element to interface with the second keying element at any point around the circumference of the second keying element. It should, therefore, be understood that the lung demand regulator may be rotatable relative to the face mask about the longitudinal axis while remaining locked to the face mask.

The first keying element may comprise a chamfered section configured to contact the second keying element so as to automatically actuate the at least one release element when the lung demand regulator is pushed onto the face mask.

It should be understood that the force applied when pushing the lung demand regulator onto the face mask may actuate the at least one release element by converting the force substantially parallel with the longitudinal axis to a force substantially radial to the longitudinal axis via the interfacing of the chamfered section and the second keying element.

According to a second aspect, there is provided a breathing gas delivery system comprising a lung demand regulator according to the first aspect, and a face mask for connection to the lung demand regulator. The face mask may comprise a complementary connector for releasable connection to the connection mechanism of the lung demand regulator.

According to a third aspect, there is provided a breathing apparatus comprising a lung demand regulator according to the first aspect. The aspects described herein provide a mechanism for automatically disabling the flow of breathing gas through the lung demand regulator when the user connects or disconnects the lung demand regulator from the face mask, hence reducing the possibility of breathing gas being wasted when the lung demand regulator is not in use. The flow of breathing gas can be reenabled by the user inhaling through the lung demand regulator as normal. The automatic disablement of the breathing gas flow is achieved by translating the force applied to the at least one release element to the lockout mechanism, via the cam element and cam follower arrangement.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG.1, an example breathing apparatus10is shown. The breathing apparatus10is a self-contained breathing apparatus (SCBA) and comprises a support frame or backplate12, straps14for securing the SCBA to a user, a breathing gas cylinder16, a face mask18, a lung demand regulator100connectable to the face mask18, and a pneumatics system20for delivering breathing gas from the cylinder16via a hose or flexible conduit22to the lung demand regulator100, to thereby deliver breathing gas to the user wearing the face mask18on demand. The breathing apparatus10may further comprise other components or systems which are not shown, including but not limited to an electrical system, a monitoring system, or a communications system. The lung demand regulator100is referred to as the regulator100throughout.

In this illustrated arrangement, the breathing apparatus is a self-contained breathing apparatus (SCBA), but it should be understood that the lung demand regulator may also have applications in other types of breathing apparatus, such as self-contained underwater breathing apparatus (SCUBA) and emergency escape breathing apparatus.

FIG.2schematically shows a face mask18attached to the regulator100. As shown in more detail inFIG.2, a hose22of the pneumatics system20is connected to an inlet101of the regulator100to provide breathing gas from the cylinder16. The pneumatics system20may comprise a first-stage pressure reducer which reduces the pressure of the breathing air from the cylinder which may be stored at several hundred bar, to an intermediate pressure for provision to the regulator100via the hose22. The intermediate pressure may be too high for the breathing gas to be provided directly to the user to breathe. The regulator100may further comprise a second-stage pressure reducer which further reduces the pressure of the breathing gas to a suitable pressure for delivery to the user to breathe. In other arrangements, more than two or fewer than two pressure reducers may be provided.

FIGS.3A,3B, and3Cschematically show the regulator100in more detail.FIG.3Ashows a cross-sectional view of the regulator100on the plane A-A shown in theFIG.2.FIG.3Bshows a cross-sectional view of the regulator100on the plane B-B shown in FIG.3A.FIG.3Cshows a further cross-sectional view of the regulator100on the plane C-C shown inFIG.3A.

As shown in theseFIGS.3A-C, the regulator100comprises a flow regulation mechanism120for regulating a flow of breathing gas. InFIGS.3A-C, the flow regulation mechanism120is shown in a closed configuration in which breathing gas flow is substantially prevented. The flow regulation mechanism120comprises a plunger122, a spring124, and a seal126. When in the closed configuration, the seal126contacts a seal seat128, thereby substantially preventing the breathing gas from flowing. An open configuration of the flow regulation mechanism120is illustrated inFIGS.4A-C, as discussed further below. Identical features are labelled with the same references acrossFIGS.3A-Cand4A-C.

The flow regulation mechanism120is actuated by the flow regulation lever170and the secondary lever180. The flow regulation lever170includes a protrusion close to its pivot (the flow regulation lever pivot174) which, as the flow regulation lever rotates in an anticlockwise direction, presses against the secondary lever180, causing the secondary lever180to also rotate about the secondary lever pivot182. The secondary lever180pushes against the plunger122of the flow regulation mechanism120, causing it to move, lifting the seal126away from the seal seat128. The further the flow regulation lever170rotates in an anticlockwise direction, the further the seal126will be lifted away from the seal seat128, increasing the rate of flow of breathing gas.

The flow regulation lever170, which comprises a flow regulation lever foot172, is rotated as a result of movement of the diaphragm106. The diaphragm106moves when there is a difference in pressure between the regulator chamber103and the ambient pressure.

Starting from a state where the flow regulation mechanism120is in the closed configuration and there is no breathing gas flowing, the user can inhale causing a drop in pressure in the regulator chamber103compared to the ambient pressure. The pressure differential causes the diaphragm106to move inwards. As the diaphragm106moves inwards, the flow regulation lever foot172is contacted by the diaphragm106, causing the flow regulation lever170to rotate anticlockwise. The resulting anticlockwise movement is translated through the secondary lever180to the plunger122, lifting the seal126off the seal seat128. As a result, breathing gas can begin to flow. In many examples, this process will occur rapidly so as not to deprive the user of breathing gas as they inhale. In some configurations, the flow regulation mechanism120may be balanced such that, in a neutral position with no pressure differential across the diaphragm106, the seal126is slightly separated from the seal seat128(i.e., a nearly-closed configuration) to provide a small constant flow of breathing gas to maintain positive pressure in the face mask18, thereby preventing ambient gas ingress.FIGS.4A-Cshow the flow regulation mechanism120in a more fully open configuration, such as when the user is inhaling.

Once the user stops inhaling, there is generally a pause before they begin to exhale. During this pause, breathing gas continues to flow through the flow regulation mechanism120. The flowing breathing gas gradually increases the pressure inside the regulator chamber103. The pressure further increases once the user begins to exhale. The pressure continues to increase until such point where the pressure in the regulator chamber103exceeds the ambient pressure, causing the diaphragm106to move outwards. As the diaphragm106moves outwards, the flow regulation lever foot172and thus the flow regulation lever170are no longer being held in place. Resultingly, the spring124inside the flow regulation mechanism120overcomes the forces of the incoming supply of breathing gas, moving the seal126back onto, or close to, the seal seat128. The flow regulation mechanism120is now returned to the closed or nearly-closed configuration, where the cycle can repeat.

When the user disconnects the regulator100from the face mask18, there is no longer a need to supply breathing gas to the regulator100. Some lung demand regulators include a manual shutoff button which discontinues the flow of breathing gas. Users may not remember to activate the shutoff and therefore breathing gas may continue to flow and be wasted. The present disclosure includes an automatic lockout mechanism105(auto-lockout mechanism105) which automatically moves the flow regulation mechanism120into the closed configuration when the user disconnects the regulator100from the face mask18.

In this example, the auto-lockout mechanism105comprises three components: a retention lever160, a lockout actuator150and a lockout lever190. The retention lever160is configured to pivot on substantially the same plane as the flow regulation lever170about the retention lever pivot166. The distal end of the retention lever160, furthest from the retention lever pivot166, lies on the top surface of the flow regulation lever foot172. A holding element162of the retention lever160on the opposite side of the retention lever pivot166interacts with a spring164to bias the retention lever160to two positions at either end of the range of motion of the retention lever160. The two positions correspond to locked and unlocked.

When the auto-lockout mechanism105is activated, the retention lever160is in the locked position, and when the auto-lockout mechanism105is deactivated, the retention mechanism160is in the unlocked position.

The lockout lever190comprises a lever stop194and a lever finger192. The lockout lever190pivots about the lockout lever pivot196on substantially the same plane as the flow regulation lever170and retention lever160.

As the lockout lever190rotates anticlockwise as shown inFIG.3A, the lever finger192contacts the retention lever160. As the lockout lever190continues to push on the retention lever160, the retention lever160contacts the top surface of the flow regulation lever foot172. As the lockout lever190rotates further still, it begins to cause the flow regulation lever170to rotate in a clockwise direction as shown inFIG.3A. This results in the flow regulation mechanism120being moved towards its closed configuration. During this rotation of the flow regulation lever170, the diaphragm106is pushed outwards by the flow regulation lever foot172.

Eventually, the lockout lever190moves the flow regulation lever170and retention lever160far enough to engage the biasing of the holding element162and spring164, thus activating the auto-lockout mechanism105and locking-out the flow regulation lever170and the diaphragm106in the closed position. In some examples, a detent may be provided to secure the retention lever160in the locked position.

The auto-lockout mechanism can be automatically deactivated by the user inhaling. Inhalation causes the diaphragm106to move inwards, resulting in the flow regulation lever170and retention lever160rotating anticlockwise. The biasing of the holding element162and spring164(and/or detent if present) is overcome and the retention lever160is moved to its unlocked position.

The lever stop194of the lockout lever190is configured to limit the maximum permissible rotation of the lockout lever190by contacting the body of the regulator100when the limit is reached. In many examples, this limit will be set at the point where the lockout lever190can rotate just far enough to activate the auto-lockout mechanism and thus set the flow regulation mechanism120in the closed configuration. The limit may also be set at a point prior to undue tension being applied to the diaphragm106by the flow regulation lever170.

Rotation of the lockout lever190is caused by the lockout actuator150pushing the lockout lever190at a position between the lockout lever pivot196and the lever finger192. This converts the linear force delivered by the lockout actuator150into a turning moment of the lockout lever190. The lockout actuator150contacts the lockout lever190at a first position on the lockout lever190. The lever finger192contacts the retention lever160at a second position on the lockout lever190. The distance between the first position and the lockout lever pivot196is a first distance. The distance between the second position and the lockout lever pivot196is a second distance. The ratio between the first distance and second distance determines the size of the travel distance of the lever finger192compared to the travel distance of the lockout actuator150, as well as the magnitude of the force translated.

Presently disclosed, the first and second distances on the lockout lever190result in a magnification of the travel distance and a diminishment of the force translated. This configuration may aim to ensure the flow regulation lever170and retention lever160can be moved far enough, while limiting the chance of damage occurring to the diaphragm106.

The lockout actuator150is positioned to operate between the regulator chamber103and the ambient atmosphere, passing through the body of the regulator100. A seal152is used to maintain isolation between the atmosphere of the regulator chamber103and the ambient atmosphere.

The lockout actuator150is moved by the two release elements140. Shown more clearly inFIG.3B, the release elements140each include a cam element146with a first chamfered face and the lockout actuator150includes a cam follower154with a second chamfered face.

As the release elements140are pressed together by the user (as shown inFIG.3B), the space between the cam elements146reduces, engaging the cam follower154and causing the cam follower154to move up the chamfer of the cam elements146. This translates the force applied to the cam elements146by the user to the lockout actuator150. The lockout actuator150moves in a direction substantially parallel to the longitudinal axis of an outlet port102.

In the present disclosure, the angles of the chamfers of the cam elements146and cam follower154are substantially complimentary so as for the surfaces of the chamfers to be parallel. The resulting arrangement may effectively translate the force between the cam elements146and cam follower154, while reducing the chance of the cams catching. In other examples, the angles of the first and second chamfers may not complement each another. In other examples still, only the cam elements146or cam follower154may comprise a chamfered face. In these alternative examples, the force may still be translated therebetween.

The cam elements146and cam follower154may be made from the same or different materials. The same or different materials may have a suitably low coefficient of friction to ensure the cam elements146and cam follower154can slide past each other with suitably low resistance. The same of different materials may also be suitably resistant to repeated abrasive contact. In lung demand regulators with moving parts, reliable operation is important. Friction between parts may be minimised to reduce wear.

The release elements140in the present disclosure are movable in a substantially radial direction relative to a longitudinal axis of the outlet port102of the flow regulation mechanism120. In other examples, the release elements140may be movable in a different direction, for instance parallel to the longitudinal axis or circumferential tot he outlet port102.

The release elements140are buttons on the outside of the regulator100. Buttons of this type may have a high grip surface finish, for instance rubber, to ease operation for the user. If, as in the present disclosure, a regulator100has two release elements140, they may be positioned on opposite sides of the regulator100so the user can press both simultaneously using one hand. Alternative examples may have a different number of release elements with different placements.

In this example, the release elements140are biased so as to return to their inactive (unpressed) position once the user releases them. A spring element may act upon the release elements140to provide a suitably resistive force to reduce the likelihood of accidental actuation. The resistive force may, for example, be derived from a spring, or from the force exerted by the diaphragm106.

Shown inFIG.3C, the two release elements140also each comprise a first keying element142.

The first keying elements142include one protrusion and one depression. The second keying element144on the face mask18also includes one protrusion and one depression. The protrusions of the first keying elements142are of substantially similar height to the depth of the depression of the second keying element144, and the protrusion of the second keying element144is of substantially similar height to the depth of the depressions of the first keying elements142. Therefore, the first keying elements142and second keying element144are able to lock together securely.

In other examples, the first keying elements142may comprise more than one protrusion and more than one depression which are configured to complement a complementary second keying element144on a face mask18to which the regulator100may be connected.

The first keying element142and the second keying element144are configured to permit rotation of the regulator100about the longitudinal axis relative to the face mask18. In the present disclosure, the second keying element144is an annular shape with a continuous cross section profile, thus allowing the first keying elements142to interface with the second keying element144at any point around the circumference. Given this freedom to interface at any orientation, the regulator100can rotate relative to the face mask18about the longitudinal axis.

In the present disclosure, the regulator100transfers breathing gas to the face mask18via the outlet port102. The outlet port102is substantially circular in plan. This permits the regulator100to rotate about the outlet port102. However, alternative examples may use different shaped outlet ports. Other examples of lung demand regulators may not include an outlet port, and instead interface with an inlet port on a face mask. The outlet port102is configured with a sealing ring104to substantially prevent breathing gas from escaping from the connection between the outlet port102and the face mask18.

The first keying elements142each also comprise a chamfered section configured to contact the second keying element144so as to automatically actuate the release elements140when the regulator100is pushed onto the face mask18. The force applied when pushing the regulator100onto the face mask18actuates the release elements140by converting the force substantially parallel with the longitudinal axis to a force substantially radial to the longitudinal axis via the interfacing of the chamfered sections and the second keying element144.

In some examples, a chamfered section may instead be located on the second keying element144, or on both the first keying elements142and second keying element144. In further examples, neither the first keying elements142nor the second keying element144may comprise a chamfered section. It should be understood that in these examples, the user would be required to press in the release elements140before pushing the regulator100on to the face mask18.

The user removes the regulator100from the face mask18by pressing the release elements140. This disengages the first keying elements142from the second keying element144, so the regulator100can be removed from the face mask18. At the same time, pressing the release elements140causes a force to be translated to the lockout actuator150via the cam elements146and cam follower154. The movement of the lockout actuator150causes the lockout lever190to rotate, which in turn causes the flow regulation lever170and retention lever160to rotate. This results in the flow regulation mechanism120moving to the closed configuration and the retention lever being held in the locked position—automatically disabling the flow of breathing gas.

The regulator100of the present disclosure may provide a more convenient and less wasteful mechanism for automatically disabling the flow of breathing gas through the regulator100when the user connects or disconnects the regulator100from the face mask18.

As the flow of breathing gas can be controlled automatically by the user connecting or disconnecting the regulator100from the face mask18, there is a reduced likelihood of breathing gas being wasted. A cam element146and cam follower154arrangement is used to operably connect the release elements140to the auto-lockout mechanism105. This cam element146and cam follower154arrangement may result in an improvement in reliability as the number of moving parts may be reduced compared to other arrangements. Further, the responsiveness of the mechanism may be improved by reducing the number of components between which force may be translated. As a result of using a reduced number of components, the arrangement may be more compact and fit into a smaller space inside the regulator100. As a result, manufacturing of the regulator100may be simplified, lifespan may be improved, and/or the overall size of the regulator100may be reduced.

As the flow of breathing gas can also be enabled automatically by the user inhaling, the regulator100of the present disclosure is easy and convenient to use, with reduced opportunity for user error.

It should be appreciated that the exemplary arrangement disclosed is one of many possible configurations for automatically disabling the supply of breathing gas when the lung demand regulator is disconnected from the face mask, using a cam and follower arrangement. Where another automatic disablement configuration is used, it should be understood that the principles of the present disclosure could be applied and adapted to provide an automatic disablement of breathing gas flow.