Bypass valve

Abstract

There is disclosed a bypass valve for providing a constant flow of breathing gas through a lung demand regulator, the bypass valve comprising a body and a plunger disposed in the body, the plunger being configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve and an open configuration in which breathing gas is permitted to flow through the bypass valve; wherein the plunger forms an inlet opening between the plunger and the body for gas to enter the bypass valve and the body comprises an outlet opening for gas to exit the bypass valve, wherein the outlet opening defines a maximum gas flow rate through the bypass valve. Also disclosed is a lung demand regulator and a breathing apparatus.

Description

Bypass ValveTechnical Field

[0001] This disclosure relates to bypass valves and, more specifically to bypass valves for providing a constant flow of breathing gas through a lung demand regulator.Background

[0002] Breathing apparatus commonly comprises a second-stage regulator, which is also known as a ‘lung demand regulator’ or ‘demand regulator’. The demand regulator is configured to deliver breathing gas to the user via a mask at a suitable pressure for breathing. A demand regulator generally comprises a demand valve which supplies breathing gas to a user via a face mask in response to a user inhaling. Proper functioning of the demand valve is crucial to keep the user out of danger. However, given the extreme conditions in which breathing apparatus are used, it is occasionally possible for a demand valve of a demand regulator to fail. A demand valve can fail in a way that leads to increased danger for a user. For example, a demand valve or the mechanism operating the demand valve could fail in a manner which partially or entirely ceases to provide adequate breathing gas to the user.

[0003] To mitigate these issues, demand regulators often include a bypass valve that can be activated (i.e. , opened) to supply a constant flow of breathing gas to the user, thereby bypassing the demand valve.

[0004] It will therefore be appreciated that improvements to existing bypass valves would be desirable.Summary

[0005] Aspects of the present invention will now be described.

[0006] According to a first aspect, there is provided a bypass valve for providing a constant flow of breathing gas through a lung demand regulator. The bypass valve may comprise a body and a plunger disposed in the body. The plunger may be configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve and an open configuration in which breathing gas is permitted to flow through the bypass valve. The plunger may form an inlet opening between the plunger and the body for gas to enter the bypass valve. The body may comprise an outlet opening for gas to exit the bypass valve. The outlet opening may define a maximum gas flow rate through the bypass valve.

[0007] The plunger may form the inlet opening when in an open position corresponding to the open configuration. The open position may be a maximally displaced position of the plunger.

[0008] The inlet opening may be configured to permit gas flow through the inlet opening at a first rate. The outlet opening may be configured to permit gas flow through the outlet opening at a second rate. The first rate may be greater than the second rate.

[0009] The inlet opening may comprise a first cross-sectional area. The outlet opening may comprise a second cross-sectional area. The first cross-sectional area may be greater than the second cross-sectional area.

[0010] The plunger may be arranged axially within a bore of the body.

[0011] The inlet opening may comprise an annular cross section arranged around the plunger between plunger and the bore.

[0012] The outlet opening may extend radially from the bore. The outlet opening comprises a circular cross section.

[0013] In the open configuration, a flow path through the bypass valve may be most restricted by the outlet opening.

[0014] The outlet opening may comprise a diameter of between 1 mm and 2 mm. The outlet opening may comprise a diameter of 1.4 mm. The diameter of the outlet opening may be determined (e.g., set) according to a nominal or working pressure of breathing gas supplied to the bypass valve. Where breathing gas intended to be supplied to the bypass valve at between 6 bar and 8 bar, the diameter of the outlet opening may be around 1.4 mm.

[0015] The outlet opening may comprise a cross-sectional area of between 3 mm and 15 mm. The outlet opening may comprise a cross-sectional area of around 6 mm.

[0016] The plunger may be configured to move between an open position corresponding to the open configuration and a closed position corresponding to the closed configuration. A displacement distance between the open position and the closed position may be fixed. The displacement distance may be at least 2 mm.

[0017] The outlet opening may comprise a fixed cross-sectional area.

[0018] In the open configuration the inlet opening may comprise a cross-sectional area at least 5% greater than the fixed cross-sectional area of the outlet opening. In the open configuration the inlet opening may comprise a cross-sectional area at least 10% greater than the fixed cross-sectional area of the outlet opening.

[0019] The cross-sectional area of the inlet opening may vary between 0 mm2in the closed configuration and a value greater than the cross-sectional area of the outlet opening in the open configuration. The cross-sectional area of the inlet opening may be around 1.7 mm2.

[0020] The plunger may comprise a fixed length. The term “fixed length” will be understood to mean that a length of the plunger cannot be altered or adjusted. According to a second aspect, there is provided a bypass valve. The bypass valve may be for providing a constant flow of breathing gas through a lung demand regulator. The bypass valve may comprise a body and a plunger disposed in the body. The plunger may be configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve and an open configuration in which breathing gas is permitted to flow through the bypass valve. The plunger may be a unitary component comprising: an engagement portion configured to be engaged by a user to move the bypass valve from the closed configuration to the open configuration; and an elongate portion. The elongate portion may be configured to block the constant flow of breathing gas in the closed configuration.

[0021] The term ‘unitary component’ should be understood as meaning that the engagement portion and the elongate portion are formed integrally as a single component.

[0022] The elongate portion may comprise a circular cross-sectional profile.

[0023] The elongate portion may comprise a first annular sealing portion having a first diameter, a second annular sealing portion having a second diameter, and an annular gas flow portion between the first annular sealing portion and the second annular sealing portion. The annular gas flow portion may have a third diameter smaller than each of the first diameter and the second diameter.

[0024] The first annular sealing portion may be a distal annular sealing portion. The second annular sealing portion may be a proximal annular sealing portion. In this context, the proximal annular sealing portion may be closer to the engagement portion than the distal annular sealing portion.

[0025] The first diameter may be equal to the second diameter. The first diameter may be smaller than the second diameter. The second diameter may be smaller than the first diameter.

[0026] The plunger may comprise: a closed configuration in which the first annular sealing portion and the second annular sealing portion seal against an internal surface of the body; and an open configuration in which the first annular sealing portion seals against the internal surface of the body, and the first annular sealing portion and at least part of the gas flow portion extend from an inlet opening of the body.

[0027] In the closed configuration, breathing gas may be prevented from entering the inlet opening by the second annular sealing portion. In the open configuration, breathing gas may be permitted to flow through the inlet opening.

[0028] The plunger may move from the closed configuration to the open configuration when an axial force is applied to the engagement portion.

[0029] The plunger may be biased into the closed configuration by a biasing element.

[0030] The first sealing portion and the second sealing portion may each comprise an annular sealing element configured to seal against a corresponding sealing surface of the body. Each sealing portion may comprise an O-ring disposed in a radially inset groove.

[0031] The ratio of the first diameter to the third diameter may be between 1.5 and 2.

[0032] The body may comprise a pin configured to engage a first keying portion of the engagement portion when the plunger is in the closed configuration. The pin may be configured to engage a second keying portion of the engagement portion when the plunger is in the open configuration to prevent the plunger from returning to the closed configuration.

[0033] The plunger may be machined from a single piece of material. The plunger may be additively manufactured as a unitary component. The plunger may be cast as a unitary component. The plunger may be seamless component.

[0034] The plunger may be configured to be displaced within the body between a closed position corresponding to the closed configuration and an open position corresponding to the open configuration.

[0035] The plunger may be configured to be axially displaced within the body between the closed position and the open position. Displacement of the plunger within the body may be between 2 mm and 5 mm. Displacement of the plunger within the body may be 3 mm.

[0036] According to a third aspect, there is provided a lung demand regulator comprising a bypass valve according to the first aspect or the second aspect. The lung demand regulator may optionally further comprise a demand valve.

[0037] According to a fourth aspect, there is provided a breathing apparatus comprising lung demand regulator according to the third aspect and / or a bypass valve according to either of the first or second aspects.Brief Description of the Drawings

[0038] Arrangements of the invention will now be described, by way of example, and with reference to the accompanying drawings, in which:

[0039] Figure 1 shows a breathing apparatus;

[0040] Figure 2 shows a lung demand regulator connected to a face mask;

[0041] Figures 3, 4A and 4B show cross sectional views of a known bypass valve; and

[0042] Figures 5, 6A and 6B show cross sectional views of a bypass valve according to an embodiment.Detailed Description of the Drawings

[0043] As noted above, the present disclosure generally relates to bypass valves for providing a constant flow of breathing gas through a lung demand regulator. Bypass valves according to the present invention may comprise a body and a plunger disposed in the body. The plunger may be configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve and an open configuration in which breathing gas is permitted to flow through the bypass valve. The plunger may form an inlet opening between the plunger and the body for gas to enter the bypass valve. The body may comprise an outlet opening for gas to exit the bypass valve. The outlet opening may define a maximum gas flow rate through the bypass valve.

[0044] The plunger may be a unitary component comprising: an engagement portion configured to be engaged by a user to move the bypass valve from the closed configuration to the open configuration; and an elongate portion, the elongate portion being configured to block the constant flow of breathing gas in the closed configuration.

[0045] As noted above, bypass valves of the present disclosure may be used with or incorporated into lung demand regulators. Such lung demand regulators often form part of a breathing apparatus.

[0046] With reference to Figure 1, an example breathing apparatus 10 is shown. The breathing apparatus 10 is a self-contained breathing apparatus (SCBA) and comprises a support frame or backplate 12, straps 14 for securing the SCBA to a user, a breathing gas cylinder 16, a face mask 18, a lung demand regulator 100 connectable to the face mask 18, and a pneumatics system 20 for delivering breathing gas from the cylinder 16 via a hose or flexible conduit 22 to the lung demand regulator 100, to thereby deliver breathing gas to the user wearing the face mask 18 on demand. The pneumatics system 20 is connected to the breathing gas cylinder 16 via a valve 19.

[0047] The breathing apparatus 10 may further comprise other components or systems which are not shown, including but not limited to an electrical system, a monitoring system, and / or a communications system. The lung demand regulator 100 may be referred to as the regulator 100 throughout.

[0048] In this illustrated arrangement, the breathing apparatus 10 is a self-contained breathing apparatus (SCBA), but it should be understood that the lung demand regulator 100 may also have applications in other types of breathing apparatus, such as self-contained underwater breathing apparatus (SCUBA) and emergency escape breathing apparatus.

[0049] Turning to Figure 2, a schematic view of a face mask 18 attached to the regulator 100 is shown. A hose 22 of the pneumatics system 20 is connected to the regulator 100 to provide breathing gas from the cylinder 16 to the regulator 100. Thepneumatics system 20 comprises a first-stage pressure reducer 21 which reduces the pressure of the breathing gas from the cylinder 16 which may be stored at several hundred bar (e.g., 400 bar), to an intermediate pressure (e.g., 7 bar) for provision to the regulator 100 via the hose 22. The intermediate pressure may be too high for the breathing gas to be provided directly to the user to breathe. The regulator 100 or the pneumatics system 20 furthers comprise a second-stage pressure reducer (shown in Figure 3 as the demand valve 110) 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. In some arrangements, the regulator 100 is connected to a pressurised breathing gas circuit such as a ring main for workers to use (e.g., in a factory).

[0050] While demand valves are designed to be extremely robust and reliable, part of ensuring reliability of the overall breathing apparatus 10, is providing failsafe systems that can compensate in case a demand valve were ever to fail. One such failsafe system is a bypass valve.

[0051] Figure 3 shows a regulator 100 comprising a known type of bypass valve 200. The view in this figure is a cross-sectional view taken from the plane A-A shown in Figure 2. The regulator 100 includes a body 102 which defines an internal cavity 104. When the regulator 100 is connected to a face mask 18, the internal cavity 104 is in fluid communication with the face mask 18 and thus the user’s lungs.

[0052] As shown, the regulator 100 includes a demand valve 110. The role of the demand valve 110 is to provide breathing gas received from the hose 22 into the internal cavity 104 for the user to breathe when responding to an incident having an unbreathable or dangerous ambient atmosphere. The demand valve 110 provides breathing gasintermittently from the hose 22 into the internal cavity 104 in response to the user inhaling.

[0053] Disposed in the body 102 is a diaphragm (not shown) with one side exposed to pressure in the internal cavity 104 and the other side exposed to ambient pressure. Inhalation by the user causes a decrease in the pressure in the internal cavity 104 relative to the ambient pressure, which causes the diaphragm to flex inwards into the internal cavity 104. The movement of the diaphragm is transferred to the demand valve 110 via one or more levers and / or mechanical linkages (not shown), which in turn causes the demand valve 110 to open, supplying breathing gas into the internal cavity 104. The supply of breathing gas into the internal cavity 104 causes the pressure in the internal cavity 104 to increase, which moves the diaphragm in the opposite direction - in turn closing the demand valve 110. This cycle repeats with each breath the user takes. During normal operation of the breathing apparatus 10, the regulator 100 delivers breathing gas in this ‘demand’ mode, whereby the demand valve 110 delivers breathing gas on demand (i.e., when the user inhales and activates the diaphragm mechanism). However, in the event of some failure of the diaphragm, its linking mechanism, or the demand valve 110 itself, there is a need for an override or ‘bypass’ which delivers a constant flow of breathing gas without the need for the complex demand valve arrangement to be operational. Therefore, a bypass valve 200 is provided.

[0054] The bypass valve 200 includes a number of separate components that are connected together. Specifically, the bypass valve 200 includes an elongate portion 202 that is threadedly connected to an engagement portion 204 and a spring retainer 206. The spring retainer 206 compresses a spring 208, causing the spring 208 to exert a reactive force on the spring retainer 206. This reactive force results in the threadedlyconnected elongate portion 202 and engagement portion 204 assembly to be urged leftward (from the perspective of Figure 3).

[0055] As noted above, the bypass valve 200 is for providing a constant flow of breathing gas through the lung demand regulator 100. The bypass valve 200 comprises a body 201 and a plunger disposed in the body 201. The plunger comprises the elongate portion 202 and the engagement portion 204. The plunger is configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve 200 and an open configuration in which breathing gas is permitted to flow through the bypass valve 200.

[0056] Figure 4A shows a magnified view of the known bypass valve 200 in isolation. In Figure 4A, the bypass valve 200 is shown in the closed configuration. The engagement portion 204 is configured to be engaged by a user to move the bypass valve 200 from a closed configuration to an open configuration. The elongate portion 202, which is threadedly connected to the engagement portion 204, is configured to block a constant flow of breathing gas through the bypass valve 200 in the closed configuration.

[0057] At an end of the elongate portion 202, opposite the engagement portion 204, there is a first sealing portion 211 and a second sealing portion 212. The first sealing portion 211 may be considered a distal sealing portion because it is arranged distally from the engagement portion 204. The second sealing portion 212 may be considered a proximal sealing portion because it is arranged proximally to the engagement portion 204 (relative to the first sealing portion 211).

[0058] The first and second sealing portions 211, 212 are annular sealing portions that are configured to seal against an internal surface of an annular bore 203 of a body201 of the bypass valve 200 in the closed configuration of the bypass valve 200. As shown, in Figure 4A, the first and second annular sealing portions 211, 212 are sealed against the bore 203. This prevents any breathing gas from flowing between the plunger and the body 201.

[0059] Between the first and second sealing portions 211, 212 is a gas flow portion 213. The gas flow portion 213 has a smaller size than the first and second sealing portions 211, 212, so does not contact or seal against the internal surface of the bore 203. In other words, a void 214 is formed between the gas flow portion 213 and the internal surface of the bore 203. In the closed configuration, the sealing of the first and second annular sealing portions 211, 212 against the bore 203 prevents breathing gas from flowing into the void 214.

[0060] To activate the bypass valve 200 (i.e., to move the bypass valve 200 from the closed configuration to the open configuration), a user can push in the engagement portion 204, against the biasing of the spring 208. Once pushed in, the engagement portion 204 can be rotated to lock the plunger in the ‘pushed-in’ position corresponding to the open configuration.

[0061] Figure 4B shows the known bypass valve 200 in the open configuration. In the open configuration, the elongate portion 202 partially extends from an end of the bore 203 to form an inlet opening 205 at the end the bore 203. The elongate portion 202 extends such that the first sealing portion 211 extends out of the bore 203, so that the first sealing portion 211 no longer seals against the internal surface of the bore 203. As a result, in the open configuration, breathing gas supplied by the hose 22 is permitted to flow through the inlet opening 205. Specifically, breathing gas is permitted to flow through the inlet opening 205, past the first sealing portion 211, around the gas flow portion 213,and out of an outlet opening 207. The breathing gas flows out of the outlet opening 207 and into the internal cavity 104 of the regulator 100, thereby supplying the user with a constant flow of breathing gas.

[0062] It will therefore be appreciated that displacement of the plunger relative to the body 201 enables breathing gas to flow through the bypass valve 200. Importantly, in the known bypass valve 200, the extent to which the plunger is displaced within the body 201 determines the flow rate of breathing gas through the bypass valve 200. This is because the cross-sectional area of the inlet opening 205 varies according to the displacement of the elongate portion 202 in the bore 203. The further the elongate portion 202 is displaced in the bore 203 to the right (from the perspective of Figure 4B), the larger the cross-sectional area of the inlet opening 205 becomes, resulting in an increase in flow rate through the bypass valve 200. The outlet opening 207 of the bypass valve 200 is large enough such that the inlet opening 205 primarily restricts flow through the bypass valve 200. That is to say, the maximum flow rate through the bypass valve 200 is defined by the inlet opening 205 and the maximum flow rate varies according to the displacement of the plunger.

[0063] In general, gas supplied to the bypass valve 200 is at a medium pressure or intermediate pressure. This pressure is between the high pressure of breathing gas stored in the cylinder 16 and a pressure breathable by a user. The medium pressure may generally be between 6 bar and 8 bar - far too high to be supplied to a user directly. The bypass valve 200 relies on the inlet opening 205 to restrict the flow rate of breathing gas through the bypass valve 200 sufficiently to be safe for the user to breathe. If the cross-sectional area of the inlet opening 205 is too large, the pressure of the breathing gas supplied to the user may be too high and / or the constant flow of breathing gas through the bypass valve may deplete the user’s remaining stored breathing gas tooquickly. Additionally, if the cross-sectional area of the inlet opening 205 is too small, the user may not be supplied with an adequate flow rate of breathing gas to sustain them.

[0064] As noted above, existing bypass valves, such as the bypass valve 200 of Figures 4A and 4B, include several separate components that are connected together, typically in a threaded fashion. This is necessary to ensure the exact size of the inlet opening 205 can be set, while accounting for dimension variations of the plunger and bore 203.

[0065] Threaded components can be affected by temperature variations, vibrations, particulate contaminants, and other environmental conditions that can all affect the functioning of respective threads on each component. In some cases, these issues can manifest as variations in the overall length of the plunger of the bypass valve due to relative movement between the components. Changes in the length of the plunger can result in performance variations between individual bypass valves.

[0066] If over time the threaded components of the bypass valve 200 move relative to each other resulting in an increase in length of the plunger, then when the user activates the bypass valve 200, the plunger may be displaced too far relative to the bore 203. This may result in the cross-sectional area of the inlet opening 205 being too large, which could in some circumstances cause breathing gas to be depleted more quickly than desired. The inverse is also true. If over time the threaded components of the bypass valve 200 move relative to each other resulting in a decrease in length of the plunger, then when the user activates the bypass valve 200, the plunger may not be displaced far enough relative to the bore 203. This may result in the cross-sectional area of the inlet opening 205 being too small, which could in some circumstances cause breathing gas to be delivered to the user more slowly than required.

[0067] Furthermore, even if the bypass valve 200 is set perfectly and does not move over time, the threaded components of the bypass valve 200 must nevertheless be carefully arranged and tested during manufacturing of the bypass valve 200 to ensure correct flow rate characteristics through the bypass valve 200 are achieved.

[0068] Figure 5 shows a bypass valve 300 according to an embodiment of the present invention. The bypass valve 300 is shown connected to the same regulator 100 of the previous figures. In Figure 5, the bypass valve 300 is shown in the closed configuration.

[0069] As shown, the plunger of the bypass valve 300 is a unitary component. That is to say, the elongate portion 302 and the engagement portion 304 are formed together integrally as a single part. The same components between Figures 4A and 4B, and Figure 5 are labelled with the same reference numerals, incremented by 100.

[0070] Figure 6A shows a detailed view of the bypass valve 300 in isolation. In Figure 6A, the bypass valve 300 is shown in the closed configuration, where no breathing gas is flowing through the bypass valve 300. The unitary plunger of the bypass valve 300 is disposed within a body 301 of the bypass valve 300. The body 301 includes a bore 303. The elongate portion 302 is disposed within the bore 303 and is configured to move axially therein. The bore 303 comprises a circular cross-sectional profile. The elongate portion 302 also comprises a circular cross-sectional profile.

[0071] The elongate portion 302 comprises a first sealing portion 311. The first sealing portion 311 is an annular sealing portion arranged around a circumference of a distal end of the elongate portion 302. The elongate portion 302 comprises a second sealing portion 312. The second sealing portion 312 is an annular sealing portionarranged around a circumference of a distal end of the elongate portion 302. Each of the first and second sealing portions 311, 312 comprises an O-ring partially inset into a respective groove of the elongate portion 302 to retain each O-ring.

[0072] The first sealing portion 311 may be regarded as a distal sealing portion as it is arranged at a distal end of the elongate portion 302. The second sealing portion 312 may be regarded as a proximal sealing portion as it is arranged at a proximal end of the elongate portion 302.

[0073] The first sealing portion 311 has a first diameter and the second sealing portion 312 has a second diameter. In some embodiments the first and second diameters are equal. In other embodiments, such as the embodiment shown, the first diameter may be smaller than the second diameter. Between the first and second sealing portions 311 , 312 is a gas flow portion 313. The gas flow portion 313 has a third diameter that is smaller than either of the first diameter or the second diameter.

[0074] In some embodiments, the first diameter may be between 3 mm and 4 mm, the second diameter may be between 3.5 mm and 4.5 mm, and the third diameter may be between 2 mm and 3 mm. In some embodiments, the first diameter may be 3.45 mm, the second diameter may be 4.05 mm, and the third diameter may be 2.6 mm.

[0075] In the closed configuration (as shown in Figure 6A), the first and second sealing portions 311, 312 each seal against an internal surface of the bore 303. As a result, breathing gas is prevented from flowing between the plunger and the body 301 the first sealing portion 311. In the closed configuration, a helical spring 308 applies a force to the plunger to maintain (i.e., bias) the bypass valve 300 in the closed configuration.

[0076] To move the bypass valve 300 from the closed configuration to the open configuration, a user first pushes the plunger inwards (in a rightward direction from the perspective of Figure 6A) by applying an axial force to the engagement portion 304. The axial force acts against the biasing of the helical spring 308 to move the plunger inwards. Displacement of the plunger is axial within the body 301 of the bypass valve 300 between a closed position and an open position. The closed position corresponds to the closed configuration. The open position corresponds to the open configuration. In some embodiments, the plunger may be displaceable by between 2 mm and 5 mm, for example by 3 mm.

[0077] Once pushed in, the user rotates the plunger by applying a torque to the engagement portion 304 to retain the bypass valve 300 in the ‘pushed in’ position corresponding to the open configuration. In some embodiments, the engagement portion 304 may be rotated by around 90°. The engagement portion 304 may be knurled to provide additional grip to the user. The need to rotate the plunger before being pushed in prevents the bypass valve 300 from being accidentally or unintentionally activated.

[0078] Figure 6B shows the bypass valve 300 in the open configuration. In the open configuration, the first sealing portion 311 extends at least partially out of the bore 303 to form an inlet opening 305. The inlet opening 305 allows breathing gas to enter the bypass valve 300. As a result, a flow path through the inlet opening 305 and past the first sealing portion 311 is formed. Breathing gas is therefore permitted to flow through the inlet opening 305 and into the void 314 formed by the annular gas flow portion 313. From the void 314, breathing gas flows out of an outlet opening 307 and into the internal cavity 104 of the regulator 100 for the user to breathe. The user is therefore supplied with a constant flow of breathing gas. The second sealing portion 312 prevents breathing gasfrom escaping from the void 314 between the elongate portion 302 and the body 301 of the bypass valve 300.

[0079] The inlet opening 305 in the depicted embodiment takes the form of an annular opening (e.g., cross section) arranged around the plunger between the plunger and the bore 303. Meanwhile, the outlet opening 307 in the depicted embodiment takes the form of a tubular opening extending radially away from the bore 303. The outlet opening 307 of this embodiment comprises a circular cross section, though it will be appreciated that outlet openings 307 with cross sections of other shapes are also applicable.

[0080] The plunger of the bypass valve 300 is shown to extend further from the bore 303 (Figure 6B) than the plunger of the bypass valve 200 (Figure 4B). This results in the inlet opening 305 providing very little (if any) restriction of breathing gas flow through the bypass valve 300, compared to the inlet opening 205 of the known bypass valve 200. Instead, the flow rate of breathing gas through the bypass valve 300 is restricted by the outlet opening 307. In other words, the outlet opening 307 defines a maximum gas flow rate through the bypass valve 300.

[0081] As the outlet opening 307 is formed in the body 301, its dimensions are not greatly affected by environmental conditions like the threaded components of the known bypass valve 200 are. Therefore, so long as the plunger of the bypass valve 300 is pushed in, the flow rate of breathing gas through the bypass valve 300 is only determined by the outlet opening 307. The bypass valve 300 is therefore less susceptible to performance degradation or variation (e.g., temperature fluctuations and / or vibrations) than the known bypass valve 200.

[0082] In other words, the inlet opening 305 may permit breathing gas to flow therethrough at a first rate and the outlet opening 307 may permit breathing gas to flow therethrough at a second rate. As described above, the first rate is greater than the second rate such that the outlet opening 307 limits the overall flow rate through the bypass valve 300.

[0083] In order to limit the flow rates as described, the inlet opening 305 may comprise a first cross-sectional area and the outlet opening 307 may comprise a second cross-sectional area. The second cross-sectional area may be smaller than the first cross-sectional area to restrict flow through the outlet opening 307 more significantly than through the inlet opening 305.

[0084] The outlet opening 307 may comprise a diameter of between 1 mm and 2 mm. Though, it will be appreciated that the exact dimensions of the outlet opening 307 may be determined according to the magnitude of the medium pressure intended to be supplied to the bypass valve 300. In some embodiments, where the medium pressure is around 7 bar, the diameter of the outlet opening 307 may be around 1.4 mm.

[0085] The cross-sectional area of the outlet opening 307 may be between around 0.5 mm2and 1.5 mm2. For a medium pressure of 7 bar, the cross-sectional area of the outlet opening 307 may be around 6 mm2.

[0086] It will be appreciated that the cross-sectional area of the inlet opening 305 is variable between the closed configuration and the open configuration. In the closed configuration, the inlet opening 305 may not be present. In other words, in the closed configuration the inlet opening 305 may comprise a cross-sectional area of 0 mm2. In order to ensure the inlet opening 305 does not restrict the flow rate of breathing gasthrough the bypass valve 300 more than the outlet opening 307, the inlet opening 305 may comprise a cross-sectional area at least 5% or at least 10% larger than the outlet opening 307 in the open configuration.

[0087] Additionally, to ensure the required cross-sectional area of the inlet opening 305 is obtained in the open configuration, the plunger may be configured to translate within the body 301 by at least 2 mm to ensure the first sealing portion 311 sufficiently clears the bore 303.

[0088] Of course, it will be appreciated that other means for limiting the flow rates through the inlet opening 305 and / or the outlet opening 307 may also be employed. For example, sudden changes in flow direction could be employed to restrict flow through the outlet opening.

[0089] By relying on the fixed dimensions of the outlet opening 307 to restrict the flow of breathing gas through the bypass valve 300, rather than relying on a variable inlet opening (like the inlet opening 205 of the known bypass valve 200), the flow rate through the bypass valve 300 can be more predicably and repeatably set during the manufacturing process. Additionally, because the flow rate of breathing gas through the bypass valve 300 is not affected by environmental conditions, the bypass valve 300 can more reliably restrict the flow of breathing gas therethrough.

[0090] It will be appreciated that the forces applied to the engagement portion 304 must be transferred effectively to the elongate portion 302 to ensure the elongate portion 302 moves as required when the user activates the bypass valve 300. As discussed above, threaded components could disrupt this force transfer and could potentially lead to unexpected results.

[0091] Because the plunger comprises a fixed length (e.g., because it is a unitary component with the engagement portion 304 and the elongate portion 302 formed integrally with one another), when the user applies a torque or an axial force to the engagement portion 304, the elongate portion 302 moves as intended without variation in the length of the plunger.

[0092] Furthermore, as the plunger may be a unitary component, during manufacturing, there is no need to manually set the rotational position of the engagement portion 304 relative to the elongate portion 302 as would be the case if they were threadedly connected. Nor is there a need to apply a thread-locking compound to threaded components. This can lead to a more straightforward manufacturing process that reduces overall assembly and quality control testing times.

[0093] Therefore, some embodiments of the present invention utilise a plunger formed as a unitary component. Being a unitary component, force applied to the engagement portion 304 is translated most effectively to the elongate portion 302 without the force passing through any linkages (e.g., screw threads). As a result, the bypass valve 300 is more reliable. Additionally, the flow rate through the bypass valve 300 is more repeatable between activations as the length of the plunger does not vary.

[0094] In some embodiments, the unitary plunger may be machined from a single piece of material. For example, the plunger may be milled (e.g., on a computer numerical control (CNC) mill) from a metal billet. The plunger may be turned on a lathe (e.g., a manual or CNC lathe) from a metal billet. The plunger may be machined from a combination of machining steps (e.g., turning on a lathe and milling) from a metal billet. The metal billet from which the plunger may be machined may be an iron or steel billet. The metal billet may be hot-worked by forging, rolled, and / or extruded.

[0095] In some embodiments, the unitary plunger may be additively manufactured as a unitary component. For example, the plunger may be manufactured using an additive layer manufacturing process such as 3D printing. Many types of 3D printing could be used form the plunger. For example, fused deposition modelling, selective laser melting and / or selective laser sintering could be used to form the plunger.

[0096] In some embodiments, the unitary plunger may be cast as a unitary component. For example, the plunger may be sand cast or die cast. After casting, the plunger may be finished using a further manufacturing process such as machining (e.g., milling).

[0097] In some embodiments, the unitary plunger may be quenched to increase its hardness. Once formed (by any of the processes described above), the unitary plunger may be anodised.

[0098] In some embodiments of the present invention, the plunger may be considered to be a unitary, seamless, unified, homogeneous, undivided, and / or continuous component. That is to say, the plunger is made up of only one component, rather than being formed of multiple individual components connected together (e.g., by fasteners, threads, or adhesives).

[0099] As will be appreciated, the bypass valve 300 may be a discrete apparatus, separate from the regulator. The bypass valve 300 may be a modular apparatus. The bypass valve 300 may be connectable to the regulator 100 by a port 109 (Figure 5) in a side of the regulator 100. The bypass valve 300 may be connectable by, for example, a quick release fitting. On connecting the bypass valve 300 to the regulator 100, the bypass valve 300 may be in fluid communication with a further port to which the hose 22 isconnected. Therefore, the hose 22 may supply breathing gas to the bypass valve 300 when the bypass valve 300 is connected to the regulator 100.

[0100] It will be appreciated by those skilled in the art that although the invention has been described by way of example, with reference to one or more exemplary embodiments, it is not limited to the disclosed embodiments and alternative embodiments could be constructed without departing from the scope of the invention as defined by the appended claims.

Claims

24Claims1. A bypass valve (300) for providing a constant flow of breathing gas through a lung demand regulator (100), the bypass valve (300) comprising a body (301) and a plunger disposed in the body (301), the plunger being configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve (300) and an open configuration in which breathing gas is permitted to flow through the bypass valve (300);wherein the plunger forms an inlet opening (305) between the plunger and the body (301) for gas to enter the bypass valve (300) and the body (301) comprises an outlet opening (307) for gas to exit the bypass valve (300), wherein the outlet opening (307) defines a maximum gas flow rate through the bypass valve (300).

2. The bypass valve (300) of claim 1 , wherein the inlet opening (305) is configured to permit gas flow through the inlet opening (305) at a first rate and the outlet opening (307) is configured to permit gas flow through the outlet opening (307) at a second rate, the first rate being greater than the second rate.

3. The bypass valve (300) of claim 1 or 2, wherein the inlet opening (305) comprises a first cross-sectional area and the outlet opening (307) comprises a second cross-sectional area, the first cross-sectional area being greater than the second cross-sectional area.

4. The bypass valve (300) of any of the preceding claims, wherein the plunger is arranged axially within a bore (303) of the body (301).

5. The bypass valve (300) of claim 4, wherein the inlet opening (305) comprises an annular cross section arranged around the plunger between plunger and the bore (303).

6. The bypass valve (300) of claim 4 or 5, wherein the outlet opening (307) extends radially from the bore (303), and optionally wherein the outlet opening (307) comprises a circular cross section.

7. The bypass valve (300) of any of the preceding claims, wherein, in the open configuration, a flow path through the bypass valve (300) is most restricted by the outlet opening (307).

8. The bypass valve (300) of any of the preceding claims, wherein the outlet opening (307) comprises a diameter of between 1 mm and 2 mm, optionally 1.4 mm.

9. The bypass valve (300) of any of the preceding claims, wherein the plunger is configured to move between an open position corresponding to the open configuration and a closed position corresponding to the closed configuration, wherein a displacement distance between the open position and the closed position is fixed, optionally wherein the displacement distance is at least 2 mm.

10. The bypass valve (300) of any of the preceding claims, wherein the outlet opening (307) comprises a fixed cross-sectional area.

11. The bypass valve (300) of claim 10, wherein in the open configuration the inlet opening (305) comprises a cross-sectional area at least 5% greater than the fixed cross-sectional area of the outlet opening (307).

12. A bypass valve (300) for providing a constant flow of breathing gas through a lung demand regulator (100), the bypass valve (300) comprising a body (301) and a plunger disposed in the body (301), the plunger being configured to move between a closed configuration in which breathing gas is prevented from flowing through the bypass valve (300) and an open configuration in which breathing gas is permitted to flow through the bypass valve (300);wherein the plunger is a unitary component comprising:an engagement portion (304) configured to be engaged by a user to move the bypass valve (300) from the closed configuration to the open configuration; andan elongate portion (302), the elongate portion (302) being configured to block the constant flow of breathing gas in the closed configuration.

13. The bypass valve (300) of claim 12, wherein the elongate portion (302) comprises a circular cross-sectional profile.

14. The bypass valve (300) of claim 13, wherein the elongate portion (302) comprises a first annular sealing portion (311) having a first diameter, a second annular sealing portion (312) having a second diameter, and an annular gas flow portion (313) between the first annular sealing portion (311) and the second annular sealing portion (312), theannular gas flow portion (313) having a third diameter smaller than each of the first diameter and the second diameter.

15. The bypass valve (300) of claim 14, wherein the plunger comprises:a closed configuration in which the first annular sealing portion (311) and the second annular sealing portion (312) seal against an internal surface of the body (301); andan open configuration in which the first annular sealing portion (311) seals against the internal surface of the body (301), and the first annular sealing portion (311) and at least part of the gas flow portion (313) extend from an inlet opening (305) of the body (301);wherein in the closed configuration breathing gas is prevented from entering the inlet opening (305) by the second annular sealing portion (312); andwherein in the open configuration breathing gas is permitted to flow through the inlet opening (305); andoptionally wherein the plunger moves from the closed configuration to the open configuration when an axial force is applied to the engagement portion (304).

16. The bypass valve (300) of claim 15, wherein the plunger is biased into the closed configuration by a biasing element (308).

17. The bypass valve (300) of claims 14-16, wherein the first sealing portion (311) and the second sealing portion (312) each comprise an annular sealing element configured to seal against a corresponding sealing surface of the body (301).

18. The bypass valve (300) of claims 14-17, wherein the first sealing portion (311) and the second sealing portion (312) each comprise an O-ring disposed in a radially inset groove.

19. The bypass valve (300) of any of the preceding claims, wherein:the plunger is machined from a single piece of material; and / orthe plunger cast as a unitary component.

20. The bypass valve (300) of any one of claims 12-18, wherein the plunger is additively manufactured as a unitary component.

21. The bypass valve (300) of any of the preceding claims, wherein the plunger is configured to be displaced within the body (301) between a closed position corresponding to the closed configuration and an open position corresponding to the open configuration, optionally wherein the plunger is configured to be axially displaced within the body (301) between the closed position and the open position.

22. The bypass valve (300) of claim 21, wherein displacement of the plunger within the body is between 2 mm and 5 mm.

23. The bypass valve (300) of any of the preceding claims, wherein the plunger comprises a fixed length.

24. A lung demand regulator (100) comprising a bypass valve (300) according to any of the preceding claims, and optionally further comprising a demand valve.

25. A breathing apparatus (10) comprising a lung demand regulator (100) according to claim 24.

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