A mouthpiece for a rebreather has a tubular housing having opposed inhale and exhale ends, a mouth port, and a discharge port. Supported for movement within a bore of the housing is a valve assembly which is magnetically biased toward a valve-closed position preventing air in an air space of the bore from moving to the exhale end and the discharge port. As a diver exhales into the mouth port, the increase in air pressure of the air space causes the valve assembly to assume a valve-open position, exposing a transverse channel extending between the air space and the discharge port, and a recirculation air channel extending between the air space and the exhale end. A portion of the exhaled air is exhausted to the ambient environment through the discharge port, while the remainder exits the mouthpiece at the exhale end for recirculation through the rebreather.

TECHNICAL FIELD

This invention relates to rebreathers. Embodiments of the invention relate to a mouthpiece for rebreather systems. Embodiments of the invention have particular application to semi-closed circuit scuba diving rebreather systems.

BACKGROUND

Scuba diving breathing systems include open-circuit and rebreather systems. In open-circuit systems, all of the diver's exhaled air is exhausted to the ambient environment (e.g. typically, into the surrounding water). In rebreather systems, at least a portion of the diver's exhaled air is recaptured and is recycled through a breathing loop which typically includes an expandable/contractible counterlung and a carbon dioxide scrubber. Rebreather systems include one or more gas supplies, containing gas such as pure oxygen, a mixture of oxygen, nitrogen and/or helium (e.g. trimix or nitrox) and/or the like. Gas from the one or more gas supplies is injected into the breathing loop to replenish the air consumed and/or exhaled by the diver.

Rebreather systems may be provided as closed-circuit or semi-closed circuit systems. In closed-circuit systems, all of the diver's exhaled air is recaptured and recycled through the breathing loop. Closed-circuit systems typically supply a combination of pure oxygen and a diluent gas (e.g. air or trimix) to the breathing loop, and include oxygen monitoring systems to monitor and adjust oxygen levels to guard against oxygen toxicity. In semi-closed circuit systems, a portion of the diver's exhaled air is exhausted from the rebreather loop to the ambient environment (typically from a port in the breathing loop located on the diver's back) and the remainder is recaptured and recycled through the breathing loop. Semi-closed circuit systems typically supply gas mixtures (e.g. nitrox) to the breathing loop and do not require oxygen monitoring systems. Semi-closed circuit systems tend to involve fewer components and are generally lighter, more compact, and easier and safer to use and maintain than closed-circuit systems.

In rebreather systems, a diver exhales and inhales through a mouthpiece which directs an incoming supply of air from the breathing loop to the diver's mouth, and directs outgoing or exhaled air from the diver's mouth toward the breathing loop for recirculation through the breathing loop. In semi-closed circuit rebreather systems, a portion of the exhaled air is discharged or exhausted to the ambient environment, typically at an outlet in the breathing loop and away from the mouthpiece.

There is a need for a mouthpiece which may be used with semi-closed circuit rebreather systems. There is a need for a mouthpiece which exhausts a portion of the exhaled air to the ambient environment while directing the remainder of the exhaled air to the breathing loop.

SUMMARY

One aspect of the invention provides a mouthpiece for a rebreather having a breathing loop. The mouthpiece includes a tubular housing having longitudinally opposed inhale and exhale ends. The inhale end is in fluid communication with an egress of a breathing loop and the exhale end is in fluid communication with an ingress of the breathing loop.

The mouthpiece has a mouth port through which a user inhales and exhales. The mouth port leads to a bore of the housing. The mouthpiece also has discharge and recirculation air channels having openings into the bore. The discharge air channel extends transversely through a body of the housing and leads to a discharge port in fluid communication with the ambient environment. The recirculation air channel extends longitudinally through the body of the housing and leads to the exhale end.

A moveable valve component is supported for movement in longitudinal directions within the bore and is shaped to define a portion of an air space within the bore between the moveable valve component and the inhale end. The moveable valve component is biased toward a valve-closed position in which the moveable valve component: is spaced apart from the exhale end by a valve closed distance dmax; and is located to block air flow into the openings of the discharge and recirculation air channels. An increase of air pressure in the air space tends to counteract the bias and move the moveable valve component toward a valve-open position in which the distance between the moveable valve component and the exhale end is less than the valve closed distance dmaxand the openings of the discharge and recirculation air channels are exposed to permit air flow therethrough. The distance by which the moveable valve component moves toward the exhale end determines a length of the openings of the discharge and recirculation air channels exposed to permit air flow therethrough. The increase in air pressure is caused by the user exhaling through the mouth port and thereby introducing air into the air space.

The movement of the moveable valve component to the valve-open position causes an increase in the size of the air space and a corresponding reduction in air pressure. The valve-open position represents an equilibrium between forces caused by the air pressure and the bias.

The moveable valve component may be magnetically biased toward the valve-closed position. A first magnet may be disposed within the moveable valve component and a second magnet may be disposed at the exhale end. The first and second magnets are arranged with like poles facing each other.

The discharge air channel has a first width and the recirculation air channel has a second width which is larger than the first width. In particular embodiments, a number of discharge air channels, a number of recirculation air channels and the first and second widths are selected such that between approximately 20% to 30% of the exhaled air travels through the discharge air channel to the discharge port while the remainder of the exhaled air travels through the recirculation air channel to the exhale end.

DESCRIPTION

Particular embodiments provide a mouthpiece for semi-closed circuit rebreather systems which may be used in scuba diving applications and/or for other applications suitable for semi-closed circuit rebreather systems. The mouthpiece includes a valve assembly for controlling the flow of air through the mouthpiece. The valve assembly is operable to direct some of the diver's exhaled air to the ambient environment (i.e. surrounding water) through a discharge port in the mouthpiece. The valve assembly is operable to direct the remainder of the diver's exhaled air to the breathing loop for recirculation through the breathing loop. Operation of the valve assembly is controlled by the diver's breathing.

According to particular embodiments, the mouthpiece comprises an outer casing30(seeFIGS. 1A through 1E), a sleeve10housed within casing30(seeFIGS. 3A through 3F) and a valve assembly20housed within sleeve10(seeFIGS. 2A and 2B). In the illustrated embodiment, as seen inFIGS. 1A through 1E, casing30is a generally tubular piece having longitudinally opposed first open end34(“inhale end”) and second open end35(“exhale end”).

In the illustrated embodiment, portions of casing30which are proximate to opposed ends34,35comprise circumferential grooves31on the outer surface of casing30(seeFIGS. 1A and 1B). Such grooves31may be shaped for receiving corresponding O-rings, deformable clips and/or the like to facilitate attachment of the mouthpiece to hose attachments and inhale and exhale hoses (not shown). Inhale end34is couplable by way of a hose attachment to an inhale hose for carrying air to be inhaled by the diver from an egress of a breathing loop (not shown) to the mouthpiece. Exhale end35is couplable by way of a hose attachment to an exhale hose for carrying the diver's exhaled air away from the mouthpiece and to an ingress of the breathing loop.

Grooves31shown inFIGS. 1A and 1Bare not mandatory. In other embodiments, other suitable attachment mechanisms may be used to attach exhale and inhale hoses of the breathing loop to the mouthpiece. By way of non-limiting example, such attachment mechanisms may include one or more of the following: hose clamps, circlips, threaded attachments, circumferential ridges, and/or the like. In other embodiments, other forms of conduits may be used to connect mouthpiece exhale end35to the ingress of the breathing loop and mouthpiece inhale end34to the egress of the breathing loop.

A check valve (not shown), such as a mushroom valve, another type of one-way valve and/or the like, may be positioned between inhale end34and the inhale hose to ensure that air at inhale end34flows in a direction indicated generally by arrow14ofFIG. 1E, and not in the reverse direction. Valve assembly20housed within sleeve10operates to ensure that air exiting the mouthpiece at exhale end35flows in a direction indicated generally by arrow15ofFIG. 1E, and not in the reverse direction. In some embodiments, a second check valve (not shown), such as a mushroom valve, another type of one-way valve and/or the like, may be positioned between exhale end35and the exhale hose to ensure that air at exhale end35flows in the direction indicated generally by arrow15.

As best seen inFIGS. 1A,1B and1D, casing30comprises a mouth port32through which the user (e.g. a diver) inhales and exhales. Port32of the illustrated embodiment comprises outwardly extending, curved cylindrical walls32A for receiving a pliable (e.g. elastomeric) mouth bit (not shown) such as those used for mouthpieces for conventional scuba regulators and/or the like. The mouth bit typically has a U-shaped extension shaped to be received within the diver's mouth.

Casing30of the illustrated embodiment also comprises one or more discharge ports36through which air within the mouthpiece may be exhausted or discharged to the ambient environment. In some embodiments, there are a plurality (e.g. two) of discharge ports36. Each discharge port36may have one or more apertures36A. Each discharge port36includes a one-way valve assembly (not shown) which permits air from the mouthpiece to escape through apertures36A to the surrounding environment, but does not permit fluid (e.g. water) from the surrounding environment to enter the mouthpiece.

By way of non-limiting example, the one-way valve assembly at discharge port36may comprise a flexible diaphragm or flap covering apertures36A and a rigid (or semi-rigid) disc positioned over the diaphragm to hold the diaphragm in place. The diaphragm may be made of latex rubber and the disc may be made of Delrin™, for example. The diaphragm deforms or otherwise lifts away from apertures36A to allow air to escape through apertures36A when the air pressure in the mouthpiece is above a threshold level. The diaphragm returns to a closed position covering apertures36A once the air pressure in the mouthpiece drops below the threshold level. One or more screws may be inserted through the diaphragm and disc to secure the diaphragm and disc to casing30. Other fasteners may be used to secure the diaphragm and disc to casing30. In other embodiments, other forms of one-way valves may be used in combination with discharge ports36to permit air to escape from the mouthpiece while preventing the ingress of fluid (e.g. water) from the surrounding environment.

As seen inFIGS. 1B and 1C, casing30has a circumferentially elongated slot37. Slot37is shaped for receiving a selector knob51(FIGS. 3D and 3E) extending from and attached to a sleeve10housed within casing30. The diver may move selector knob51within slot37to rotate sleeve10between an “ON” position in which all ports of the mouthpiece are opened (e.g. such that aperture46through sleeve10is aligned with mouth port32, and each discharge slot41through sleeve10is aligned with a corresponding discharge port36), and an “OFF” position in which all ports of the mouthpiece are closed (e.g. aperture46and discharge slots41through sleeve10are sealed from the ambient environment as they are misaligned with their corresponding ports32,36in outer casing30). Sleeve10may be rotated to the “ON” position when the mouthpiece is being used by the diver, and may be rotated to the “OFF” position when the mouthpiece is not being used by the diver.

In the illustrated embodiment, as best seen inFIGS. 3A and 3B, sleeve10is a generally tubular piece having a first open end24(“inhale end”) and a second open end25(“exhale end”). When sleeve10is inserted into casing30, inhale end24of sleeve10is generally aligned with inhale end34of casing30, and exhale end25of sleeve10is generally aligned with exhale end35of casing30.

FIGS. 2A and 2Billustrate a valve assembly20that may be housed within sleeve10. Sleeve10and valve assembly20together are housed within casing30. In the illustrated embodiment, when valve assembly20is inserted into sleeve10, valve assembly20may be located generally proximate to exhale end25of sleeve10. An air space or chamber18is defined within sleeve10between inhale end24of sleeve10and valve assembly20.

When the mouthpiece is in use (i.e. when selector knob51and sleeve10are rotated to the “ON” position), discharge ports36are aligned with corresponding discharge slots41in sleeve10(seeFIGS. 2A,2B,2C and3A). Mouth port32in casing30(FIG. 1A) is aligned with a corresponding aperture46in sleeve10(FIG. 3A). Mouth port32and aperture46are in fluid communication with air space18such that air exhaled by the diver into the mouthpiece (via mouth port32) moves into air space18(FIGS. 2A and 2B). Conversely, air inhaled by the diver moves out of air space18, through aperture46and mouth port32, and into the diver's mouth. As explained below, the changes in air pressure in air space18resulting from the diver's breathing cause the components of valve assembly20to move, thereby controlling the discharge of exhaled air from the mouthpiece at exhale end25and at discharge ports36(via discharge slots41in sleeve10).

Valve assembly20is operable to control the flow of air from air space18toward exhale end25and discharge slots41. When valve assembly20is in the valve-closed position (e.g. seeFIG. 2A), valve assembly20prevents air in air space18from travelling toward exhale end25and discharge slots41. When valve assembly20is in a valve-open position (e.g. seeFIG. 2B), valve assembly20permits air in air space18to travel toward exhale end25and discharge slots41.

As shown inFIGS. 2A and 2B, valve assembly20comprises valve components22,23which are moveable in relation to one another. Such valve components may comprise a moveable component22and a fixed component23. Valve components22,23may be generally cylindrical in shape. In the illustrated embodiment, moveable component22is supported for movement in longitudinal (e.g. axial) directions within a generally tubular inner sleeve wall29. Inner sleeve wall29may be integrally formed with, or connected to, sleeve10. Valve components22,23may have generally parallel (or otherwise complementary-shaped), facing surfaces22A,23A, respectively.

In the illustrated embodiment, fixed component23is fixed in position relative to sleeve10, and is positioned at or close to exhale end25. A plurality of screws13or other fasteners may be used to secure fixed component23to the walls of sleeve10at or near exhale end25. In other embodiments, fixed component23may be secured to sleeve10in some other manner (e.g. deformable connectors, clasps, suitable adhesives, welding and/or the like.). In still other embodiments, fixed component23may be integrally formed with sleeve10.

In the illustrated embodiment, moveable component22is slidable between: (a) a valve-closed position in which moveable component22is separated from fixed component23at exhale end25by a maximum or valve closed distance dmax(FIG. 2A), and (b) a valve-open position in which moveable component22has moved toward fixed component23and the distance between valve components22,23is less than distance dmax.FIG. 2Bshows valve assembly20in the maximum valve-open position in which moveable component22has moved toward fixed component23by a distance such that surface22A of moveable component22abuts surface23A of fixed component23.

When moveable component22is in the valve-closed position (FIG. 2A), moveable component22is constrained from moving toward inhale end24by a stop16. For example, stop16may comprise a ridge or other protrusion(s) extending from the inside surfaces of sleeve10for engaging with corresponding surfaces of moveable component22. Stop16and the corresponding surfaces of moveable component22may be shaped to be complementary to one another (i.e. for generally airtight engagement) such that when moveable component22is in the valve-closed position, air in air space18is prevented from moving toward exhale end25and toward discharge slots41(seeFIG. 2A). In the illustrated embodiment, when valve assembly20is in the valve-closed position, air in air space18is blocked from moving into air channels21,26leading to discharge slots41and exhale end25, respectively.

In the illustrated embodiment, valve components22,23are biased apart—i.e. valve assembly20is biased to be in the valve-closed position shown inFIG. 2Ain the absence of any counteracting forces. Valve components22,23may be magnetically biased apart as described in further detail below. As the diver exhales into the mouthpiece, the air pressure in air space18initially increases since the exhaled air is trapped within air space18. When the air pressure in air space18increases beyond a level sufficient to overcome the biasing forces that are holding valve components22,23apart in the valve-closed position, moveable component22moves toward fixed component23—i.e. valve assembly20is moved to a valve-open position. The movement of moveable component22toward fixed component23results in an increase in the size of air space18and a corresponding reduction in the air pressure in air space18. The valve-open position represents an equilibrium between forces caused by the air pressure and the bias.

Movement of moveable component22toward fixed component23opens up a new air space19within sleeve10previously occupied by moveable component22(e.g. seeFIG. 2B). This can also be described as an enlargement of air space18to include the air space previously occupied by moveable component22. In the illustrated embodiment, air space19(or enlarged air space18) is in fluid communication with one or more longitudinal (recirculation) air channels26extending longitudinally between air space18and exhale end25. In the illustrated embodiment, air space19(or enlarged air space18) is also in fluid communication with one or more discharge air channels21. Each discharge air channel21may extend transversely to a corresponding discharge slot41at the outer surface or walls of sleeve10. In the illustrated embodiment (seeFIG. 2C), each discharge air channel21extends radially to a corresponding discharge slot41. Openings may be defined in inner sleeve wall29to permit air to travel from air space19to channels21and26.

As seen inFIG. 2B, during an exhale breath, moveable component22moves toward fixed component23by a distance which determines a length l of air channels21,26that is exposed to air space19. Length l varies according to the diver's breathing (e.g. a relatively strong exhale breath tends to cause moveable component22to move toward fixed component23by a greater distance, thereby causing a relatively long length l of exposed air channels21,26).

Once moveable component22has moved toward fixed component23(i.e. away from the valve-closed position and into a valve-open position), the diver's exhaled air which was previously trapped in air space18is able to move into new air space19, and into air channels21and26. As indicated inFIG. 2B, a portion of the air travelling through the mouthpiece may take the flow path indicated by arrow13A, travelling through the one or more recirculation air channels26before exiting the mouthpiece at exhale end25, after which it is recirculated through the breathing loop. Another portion of the air travelling through the mouthpiece may take the flow path indicated by arrow13B, travelling through the one or more discharge air channels21before exiting the mouthpiece at discharge slot41(and discharge port36). Air exiting through discharge slot41is exhausted to the ambient environment.

In the illustrated embodiment, as best seen inFIG. 2C, sleeve10has three recirculation air channels26each extending to exhale end25, and two discharge air channels21each extending to a corresponding discharge slot41. Each discharge slot41may be located in a corresponding recessed portion40of sleeve10. Recessed portion40provides an air space between discharge slot41and the one-way valve assembly at discharge port36(seeFIG. 1B).

In the illustrated embodiment, the three recirculation air channels26are evenly circumferentially spaced apart. Each of the two discharge air channels21extends transversely between two adjacent recirculation air channels26. Other configurations and shapes of air channels21,26are possible. For example, a different number and/or arrangement of air channels21,26may be provided than as shown in the illustrated embodiment.

As seen inFIG. 2C, the circumferential width w1of each discharge air channel21is smaller than the circumferential width w2of each recirculation air channel26. The relative proportion of air travelling through channels21,26may be determined at least in part by the minimum cross-sectional areas in the flow paths between air spaces18,19and channels21,26. In the illustrated embodiment these cross-sectional areas are defined at least approximately by the circumferential widths w1, w2of air channels21,26at the interface between air space19and air channels21,26, and a length l of air channels21,26that is directly exposed to air space19(i.e. not covered by moveable component22) as a result of movement of moveable component22toward fixed component23(seeFIG. 2B).

In particular embodiments, the magnitude of the biasing forces acting on valve components22,23is such that when a diver exhales into the mouthpiece under typical operating conditions (for example, use at a depth of up to 100 feet), moveable component22typically moves toward fixed component23by a distance which is between 30% to 80% of dmax. In such embodiments, during the exhale breath, moveable component22rarely moves completely to the maximum valve-open position in which moveable component22abuts fixed component23, as seen inFIG. 2B.

A decrease in air pressure in air space18to a level such that the force on moveable component22is less than the current bias force may result in moveable component22moving back toward inhale end24until moveable component22reaches either a new equilibrium position or the valve-closed position shown inFIG. 2A. The air pressure in air space18may be decreased as a result of: moveable component22moving toward fixed component23(thereby resulting in a corresponding expansion to air space18), the diver inhaling (thereby removing air from air space18), the diver ceasing to exhale or decreasing the strength of the exhale breath and/or air exiting space18via air channels21,26.

In particular embodiments, valve components22,23are magnetically biased apart—i.e. toward the valve-closed position shown inFIG. 2A. In the illustrated embodiment, a plurality of magnets12A,12B are embedded within valve components22,23, respectively (seeFIGS. 2A and 2B). Due to space constraints within sleeve10, fixed component23may include a cylindrical extension27, which may extend into the exhale hose, for accommodating magnets12B. Magnets12A,12B are arranged with their similar poles facing one another (i.e. magnets12A are arranged so as to repel magnets12B), resulting in biasing forces which keep valve components22,23apart in the valve-closed position, in the absence of any counteracting forces.

The rate of air being exhaled by the diver (i.e. volume of exhaled air entering the mouthpiece per time unit) determines the pressure in air spaces18,19and the corresponding distance by which moveable component22moves toward fixed component23. For higher rates of exhaled air, moveable component22moves by a correspondingly larger distance toward fixed component23, thereby increasing the exposed length l of air channels21,26and allowing air in air spaces18and19to flow into channels21,26at a higher rate. However, as the relative (i.e ratio of) minimum cross-sectional areas in the flow paths between air spaces18,19and channels21,26remains generally constant, the relative proportion of air travelling through channels21,26also remains generally constant. Therefore, the proportion of the exhaled air that is exhausted to the ambient environment through discharge slots41relative to a total amount of exhaled air remains generally constant during operation.

For a given configuration of recirculation air channels26(e.g. number, volume and circumferential width w2of channels26, etc.), a larger the number and/or circumferential width w1of discharge air channels21, the greater the proportion of exhaled air that is exhausted to the ambient environment. In particular embodiments, the number and dimension(s) (e.g. circumferential width(s) w2) of recirculation air channels26) and the number and dimension(s) (e.g. circumferential width(s) w1) of discharge air channels21are selected such that between approximately 20% to 30% of exhaled air is exhausted to the ambient environment through discharge air channels21and discharge slots41, and the remainder (i.e. between approximately 70% to 80%) of the exhaled air travels through recirculation air channels26and exits the mouthpiece at exhale end25, where it is recaptured for recirculation through the breathing loop.

A total amount of air that exhausted through both recirculation air channels26and discharge air channels21may be proportional to (or correlated with) the number of recirculation air channels26and discharge air channels21multiplied by their corresponding widths according to:
total amount exhausted ∝(# of recirculation channels)w2+(# of discharge channels)w1
Accordingly, the proportion of air that is exhausted to the ambient environment through discharge air channels21relative to the amount of total amount of exhausted air through both discharge air channels21and recirculation air channels26may be proportional to (or correlated with) the ratio of the number of discharge air channels21multiplied by their corresponding widths divided by the total amount of exhausted air according to:
proportion discharged=(# of discharge channels)w1/(# of recirculation channels)w2+(# of discharge channels)w1
In some embodiments, various discharge air channels21and/or various recirculation air channels26may be provided with different widths, in which case the foregoing equations may be adjusted accordingly.

The number and dimension(s) (e.g. circumferential width(s) w2) of recirculation air channels26) and the number and dimension(s) (e.g. circumferential width(s) w1) of discharge air channels21may vary between different embodiments rated for different skill levels, depths, dive duration, etc. For example, for recreational diving (e.g. at depths of up to 100 feet) it may be desirable to adjust one or more of these parameters such that approximately 30% of the exhaled air is exhausted to the ambient environment. For deeper or more technical diving, it may be desirable to adjust one or more of these parameters such that approximately 20% of the exhaled air is exhausted to the ambient environment. In particular embodiments, where there are two discharge air channels21and three recirculation air channels26, the ratio between circumferential widths w1and w2may be less than 0.15. In certain embodiments such ratio may be less than 0.10 and above 0.05.

It may be desirable to configure valve assembly20such that the air pressure needed to overcome the biasing forces (and other forces such as friction) holding valve components22,23apart in the valve-closed position is sufficiently low, so that during each typical exhale breath, moveable component22moves toward fixed component23(i.e. valve assembly20is moved to a valve-open position) thereby allowing exhaled air to exit at exhale end25and discharge ports36. Otherwise, if valve assembly20were to remain in the valve-closed position during an exhale breath, the exhaled air would remain trapped within air space18and could be subsequently inhaled by the diver.

In the illustrated embodiment (seeFIGS. 2A and 2B), hollow spaces17may be formed within moveable component22to reduce the component's weight. This in turn may reduce friction between the outer surfaces of moveable component22and inner sleeve wall29and may help to facilitate movement of moveable component22relative to fixed component23.

As described above, by sliding selector knob51of sleeve10within slot37of casing30, sleeve10may be rotated between an “ON” position in which all ports of the mouthpiece are opened, and an “OFF” position in which all ports of the mouthpiece are closed. As best seen inFIG. 3E, selector knob51may be surrounded by a groove42A for receiving a suitably-shaped ring seal for preventing water from entering through slot37of casing30.

Once the diver has rotated sleeve10to the “OFF” position, the diver may remove the mouth bit from his or her mouth. If the mouthpiece is kept immersed in water, the space circumscribed by the curved walls of mouth port32fills with water but the water is prevented from entering the mouthpiece given that openings into the mouthpiece (including aperture46and discharge slots41) are sealed from the ambient environment in the “OFF” position. If the diver wishes to begin using the mouthpiece while the mouthpiece is immersed in water, the diver can blow into mouth port32while sleeve10remains in the “OFF” position. In such “OFF” position, mouth port32is aligned with slot47of sleeve10(seeFIG. 3C) and slot47is in fluid communication with aperture38of casing30(seeFIG. 1E). By blowing into mouth port32, water which has been trapped within mouth port32can be expelled through slot47and aperture38into the ambient environment. A one-way valve may cover aperture38to prevent water from entering the mouthpiece through aperture38. After the water has been cleared from mouth port32in this manner, the diver may rotate sleeve10to the “ON” position and the diver may begin exhaling and inhaling through mouth port32which is now aligned with aperture46of sleeve10.

In some embodiments, one or more grooves may be provided in sleeve10at locations such that when sleeve10has been rotated to the “OFF” position, the grooves are aligned with discharge ports36of casing30. Such grooves may receive corresponding ring seals (e.g. O-ring seals) for preventing gas from leaking through discharge ports36during positive pressure testing conducted on the mouthpiece when sleeve10has been rotated to the “OFF” position.

The illustrated embodiment contains a sleeve10within an outer casing30. As described above, sleeve10may be rotated to switch the mouthpiece between “ON” and “OFF” positions. In other embodiments, sleeve10is omitted. In such embodiments, outer casing30is adapted to include the structural features of sleeve10which support the operation of valve assembly20, such as, for example:inner walls29for supporting movement of moveable component22within a bore of casing30;stop16for limiting the movement of moveable component22toward inhale end24;one or more discharge air channels21extending transversely through casing30for carrying exhaled air toward discharge slot41;one or more recirculation air channels26extending longitudinally through casing30for carrying exhaled air toward exhale end25; andrecessed portion40providing an air space between discharge slot41and the one-way valve assembly at discharge port36;
as described above with reference to sleeve10.

In the illustrated embodiment, two valve components22,23are used. Magnets are housed within each of the valve components. In other embodiments, fixed component23is omitted, and magnets are disposed within or on portions of sleeve10(or casing30) proximate to or at exhale end25. Such magnets are arranged so as to repel the other magnets disposed within moveable component22. In such embodiments, moveable component22is magnetically biased apart from the magnets positioned near exhale end25.

The embodiments described herein are only examples. As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example:A mouthpiece as described herein is not limited to use in underwater environments. The mouthpiece may be used for semi-closed circuit rebreather systems in other applications and environments where a gas is supplied for inhalation by the user, such as, for example, outer space, mining, mountaineering, submarines, and the like.The illustrated embodiment is generally tubular in shape. However, this is not mandatory. In other embodiments, the mouthpiece (including casing30and sleeve10) may have a non-tubular or non-cylindrical shape (i.e. a shape having a non-circular cross-section). Moveable valve component22may be shaped and supported for movement within non-tubular or non-cylindrical walls.Other biasing mechanisms may be used for valve assembly20, such as, for example, spring or coil biasing mechanisms.For bevity, this description and the accompanying claims refer to fluids exhaled into the mouthpiece, inhaled from the mouthpiece, discharging from the mouthpiece, ingressing into the breathing loop, egressing from the breathing loop and/or the like as “air”. It will be understood by those skilled in the art that such fluids are not limited to “air” in the conventional sense and may include other fluids (e.g. gases and gases mixed liquids), mixtures of fluids and/or the like. It will be understood further that.
Other example embodiments may be obtained, without limitation, by combining features of the disclosed embodiments.

Accordingly, this invention should be interpreted in accordance with the following claims.