DIAPHRAGM

Abstract

A diaphragm for a lung demand valve, including a CBRN layer which is sufficiently resistant to the permeation of at least some CBRN agents and a resilient layer which is resiliently deformable. The CRBN layer is arranged to restrict the permeation of at least some CBRN agents through the diaphragm, and the resilient layer is arranged to allow the diaphragm to be resiliently deformed.

Claims

1. A lung demand valve, comprising: a housing; a valve assembly for controlling the supply of breathable gas to a user; a diaphragm disposed and sealed within the housing for controlling the valve assembly and which responds to the inhalation and exhalation of the user, the diaphragm having a first outer side exposed to ambient conditions and a second inner side exposed to breathable gas, wherein the diaphragm is continuous and prevents the fluid flow across the diaphragm and is of a laminate structure comprising a resilient skeleton layer which provides resilient characteristics to the diaphragm and a continuous barrier layer arranged to restrict the permeation of at least some hazardous agents through the diaphragm.

2. A lung demand valve according to claim 1, wherein the barrier layer comprises a CBRN layer.

3. A lung demand valve according to claim 1, wherein the barrier layer is arranged to restrict the permeation of at least some CBRN agents through the diaphragm.

4. A lung demand valve according to claim 1, wherein the barrier layer is deformable.

5. A lung demand valve according to claim 1, wherein the barrier layer comprises a plastics material.

6. A lung demand valve according to claim 5, wherein the plastics material comprises polyvinylidene fluoride.

7. A lung demand valve according to claim 1, wherein the resilient skeleton layer is discontinuous.

8. A lung demand valve according to claim 1, wherein the resilient skeleton layer comprises at least one through opening.

9. A lung demand valve according to claim 1, wherein the resilient skeleton layer comprises a plurality of through openings.

10. A lung demand valve according to claim 1, wherein the resilient layer is substantially rotationally symmetric.

11. A lung demand valve according to claim 1, wherein the diaphragm is substantially rotationally symmetric.

12. A lung demand valve according to claim 1, wherein the resilient skeleton layer comprises an elastomer.

13. A lung demand valve according to claim 1, wherein the resilient skeleton layer comprises silicone.

14. A lung demand valve according to claim 1, wherein the diaphragm comprises a sealing lip that is retained by a part of the lung demand valve.

15. A lung demand valve according to claim 1, wherein the barrier layer and the resilient skeleton layer are bonded together to form a laminate.

16. A lung demand valve according to claim 1, wherein the resilient skeleton layer is on the first outer side and wherein the barrier layer is on the second inner side.

17. A lung demand valve according to claim 1, wherein the diaphragm further comprises a substantially rigid plate against which in use a spring and/or valve lever acts.

18. A lung demand valve according to claim 17, wherein the rigid plate is bonded to the resilient skeleton layer.

19. A lung demand valve according to claim 17, wherein the rigid plate is located within a through opening in the resilient skeleton layer.

20. A lung demand valve according to claim 17, wherein the barrier layer extends across the rigid plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

[0039] FIG. 1 schematically shows a cross-sectional view through a lung demand valve.

[0040] FIG. 2 schematically shows the diaphragm of the lung demand valve of FIG. 1.

[0041] FIG. 3 schematically shows an exploded view of the lung demand valve of FIG. 1.

DETAILED DESCRIPTION

[0042] FIG. 1 schematically shows a lung demand valve (LDV) 10 that is typically used in conjunction with self-contained breathing apparatus. The LDV 10 comprises a plug-in connector 12 for attaching the LDV 10 to a breathing apparatus face-mask (not shown), a breathable gas inlet 14 which is arranged to be connected to a supply of breathable gas such as a cylinder of compressed air (not shown), a valve assembly 16 for controlling the supply of breathable gas, and a diaphragm 18 for controlling the valve assembly 16. The LDV 10 is suitable for use in chemical, radiological, biological and nuclear (CBRN) environments and therefore complies with certain standards which will be described in detail below. In this particular embodiment the LDV 10 is conventional, except for the CBRN compliant diaphragm 18. In this arrangement the CBRN compliant diaphragm 18 is of a similar size to that of a conventional diaphragm and therefore a conventional LDV can be retrofitted and therefore upgraded for CBRN compliance. This can be done by simply replacing a conventional diaphragm with a CBRN compliant diaphragm 18.

[0043] The LDV 10 comprises a main housing 20 which defines an internal chamber 22. The plug-in connector 12 is attached to the housing and is in fluid communication with the internal chamber 22 through a fluid passageway 24.

[0044] The valve assembly 16 is disposed within the housing 20 and comprises a gas inlet 26 which opens into a valve chamber 28 defined by a valve housing 27. The valve assembly 16 also comprises a valve member 30 which cooperates with a valve scat 32 to open and close the valve. The valve member 30 is attached to an actuation shaft 34 and a spring 36 acts on the shaft 34 so as to bias the valve member 30 to a closed position. The shaft 34 is sealed within the valve housing with an O-ring 38. This allows the actuation shaft 34 to axially move within the valve housing to open and close the valve, whilst sealing the valve housing to prevent undesirable gas leakage. A cam follower 40 is attached to the end of the shaft 34 and cooperates with a cam 42 that is provided on the end of a pivotable lever arm 44. As will be described in detail below, the distal end 46 of the lever arm 44 cooperates with the diaphragm 18 to open and close the valve. The valve assembly 16 further comprises a breathable gas outlet 48 which is arranged to discharge breathable gas into the region of the plug-in connector 12 such that it can be breathed by a user.

[0045] The diaphragm 18 is a CBRN compliant diaphragm and is located within the housing 20. The diaphragm 18 is substantially circular and is retained within the housing by a cap 50 that is attached to the housing 20. A spring 51 is disposed between the cap 50 and the ambient side of the diaphragm 18 and therefore acts on the diaphragm 18. The diaphragm 18 is sealed within the housing such that there is no gas flow from the chamber 22 across the diaphragm 18. The cap 50 is provided with a number of openings 52 and is covered with a removable protective rubber cover 54 which is also provided with openings (not shown). This allows ambient atmosphere to both come into contact with, and act on, the diaphragm 18.

[0046] In use, the plug-in connector 12 of the LDV 10 is attached to a breathing apparatus face-mask (not shown) and the gas inlet 14 is attached to a cylinder of breathable gas (not shown). In the resting state, the diaphragm is in the position shown in FIG. 1 and the valve assembly 16 is closed such that breathable gas is not supplied to the user. As the user inhales, the pressure within the face-mask, and therefore within the chamber 22 is reduced so that it is below the ambient pressure. The pressure acting on the ambient side 18a of the diaphragm 18 is therefore greater than the pressure acting on the breathable gas side 18b of the diaphragm 18. This causes the diaphragm 18 to resiliently deform into the chamber 22. The movement of the diaphragm 18 causes the lever arm 44 to pivot in the anti-clockwise direction and the cam 42 acts on the follower 44 such that the shaft 34 axially moves to the right. The movement of the shaft 34 lifts the valve member 30 off the valve seat 32 and therefore allows breathable gas to flow from the valve chamber 28 out of the valve assembly 16 through the gas outlet 48. In this manner breathable gas is discharged into the region of the plug-in connector 12 where it flows to the face-mask such that it can be breathed by a user. As breathable gas is discharged by the valve assembly 16, the pressure within the face-mask and hence the chamber 22 increases. This causes the diaphragm 18 to return towards its original position. As the diaphragm 18 moves out from the chamber 22, the spring 36 of the valve assembly 16 acts to return the valve member 30 to a position in which it is in contact with the valve seat 32. This therefore closes the valve assembly 16 and stops the flow of breathable gas to the face-mask. When the user next inhales, the process is repeated.

[0047] There are a number of requirements that an LDV must comply with so that it can be deemed safe for use. The requirements may be any one or more of the following, the entire contents of which are incorporated herein by reference:

NIOSH 42 CFR 84

NFPA 1981

EN137

[0048] The diaphragm 18 of this embodiment has been designed such the LDV 10 complies with the above requirements. The detailed construction of the diaphragm 18 will be described below. In summary, the diaphragm 18 is suitably sensitive to differential pressure changes across the diaphragm 18 so that the LDV 10 operates correctly to supply the appropriate amount of breathable gas to the user as required. The diaphragm 18 also ensures that the LDV 10 functions correctly over the wide temperature range that may be experienced by potential users. Further, the diaphragm 18 ensures that the LDV 10 is capable of supplying breathable gas at the high breathing rates that may typically occur in use.

[0049] An LDV must also comply with various CBRN requirements, if it is to be suitable for use in CBRN environments. The requirements may be any one or more of the following, the entire contents of which are incorporated herein by reference:

NIOSH 42 CFR 84.63

BS8468-1 2006

[0050] These requirements centre around ensuring that certain CBRN agents do not permeate through the diaphragm 18 from the ambient side into the chamber 22 so as to prevent CBRN agents being inhaled by a user. NIOSH 42 CFR 84.63 is appended as Attachment A.

[0051] The diaphragm 18 of this embodiment has been designed such the LDV 10 complies with the above CBRN requirements. The detailed construction of the diaphragm 18 will be described below. In summary, the diaphragm 18 is sufficiently resistant to the permeation of at least some CBRN agents through the diaphragm 18. This ensures that in use a user does not inhale dangerous levels of hazardous CBRN agents.

[0052] It should be appreciated that the LDV 10 may also, or instead, comply with other similar requirements.

[0053] With reference to FIGS. 2 and 3, the diaphragm 18 comprises a first CBRN layer 58, which may be referred to as a barrier layer, and a second resilient layer 60, which may be referred to as a support structure. The CBRN layer 58 and the resilient layer 60 are bonded together with a layer of adhesive 62, thereby forming a laminate structure. The CBRN layer 58 and the resilient layer 60 are coextensive with one another and have a common periphery. The resilient layer 60 comprises a central opening 64 within which is disposed a rigid disc (or plate) 66. The disc 66 is fixedly attached to the resilient layer 60 and the CBRN layer 58 extends across and underneath the disc 66.

[0054] The CBRN layer 58 is a thin film of polyvinylidene fluoride (PVDF) having a thickness of approximately 0.013 mm. It should be appreciated that other suitable materials may be used for the CBRN layer 58. For example, the CBRN layer may be a polyvinyl fluoride (PVF) film, or a polyether ether ketone (PEEK) film. Further, the CBRN layer 58 may be of any suitable thickness.

[0055] The CBRN layer 58 is non-porous and impermeable and therefore acts as a barrier. In particular, the CBRN layer 58 is sufficiently resistant to the permeation of hazardous agents, such as the CBRN agents sarin and mustard gas. The CBRN layer 58 therefore acts to prevent the permeation of CBRN agents through the diaphragm. It should be noted that the CBRN layer 58 may not be completely impermeable to all CBRN agents. For example, it may be permissible that CBRN agents permeate the CBRN layer, and hence the diaphragm, in extremely small concentrations. The CBRN layer 58 may therefore only be sufficiently resistant to the permeation of at least some CBRN agents such that an LDV 10 comprising the diaphragm 18 passes appropriate CBRN tests. The appropriate test may be NIOSH 42 CFR 84.63 and/ BS8468-1 2006 or similar.

[0056] The CBRN layer 58 is also flexible and is therefore capable of being deformed. In particular, the CBRN layer 58 maintains its flexibility over a wide range of operating temperatures. This is important as the LDV 10 comprising the diaphragm 18 is required to perform correctly over a wide temperature range at various breathing rates.

[0057] The resilient layer 60 is resiliently deformable and therefore allows the diaphragm 18 as a whole to be resiliently deformed. The resilient layer 60 is made from silicone and has a thickness that varies from between 0.3-0.8 mm. It should be appreciated that any suitable material may be used for the resilient layer 60, providing it has the appropriate resilient properties. Further, the thickness may be altered depending on the specific requirements. The periphery of the resilient layer 60 comprises a sealing lip 70. When the diaphragm 18 is located within the LDV housing 20, the sealing lip 70 provides a seal between the housing 20 and the diaphragm 18 and prevents gas flow across the diaphragm 18.

[0058] The resilient layer 60 is discontinuous and is provided with a number of circumferentially spaced openings 68 (in this case eight) that are distributed equally around a circumference of the diaphragm. The resilient layer 60, and therefore the diaphragm 18 as a whole, is therefore rotationally symmetric and has rotational symmetry of order eight. Since the resilient layer 60 is rotationally symmetric, the diaphragm 18 has substantially uniform resilient characteristics. These openings 68 reduce the stiffness of the diaphragm 18 such that it responds appropriately. The stiffness of the diaphragm 18 can be increased by increasing the overall area of the resilient material (i.e. by reducing the total area of the openings) and similarly the stiffness of the diaphragm 18 can be reduced by reducing the overall area of the resilient material (i.e. by increasing the total area of the openings). It may be possible to adjust the resilient characteristics of the diaphragm 18 by only adjusting the thickness of the resilient layer 60, but this may be limiting as there may be maximum and minimum thicknesses that must be complied with. Therefore, adjusting the ratio of openings to resilient material of the resilient layer 60 provides a convenient way of modifying the resilient properties of the resilient layer 60 and hence the diaphragm 18. In some cases, adjusting the openings/resilient material ratio of the resilient layer 60 may be the only feasible way of achieving the required resilient characteristics in order to meet specific operational requirements.

[0059] The non-porous CBRN layer 58 not only acts as a barrier to hazardous agents, but also transfers the pressure differential to the discontinuous resilient layer 60. Therefore, even though the resilient layer 60 is discontinuous, the diaphragm 18 as a whole operates correctly and responds to pressure changes.

[0060] The resilient layer 60 ensures that the diaphragm 18 as a whole is sufficiently sensitive, and responds appropriately, to pressure changes across the diaphragm. This means that in use the LDV 10 performs in the desired manner and complies with the performance requirements set out in EN137, NIOSH 42 CFR 84 and NFPA 1981. It may be necessary to alter the ratio of openings to resilient material of the resilient layer 60 to meet the requirements so that the LDV 10 operates correctly and meets the performance requirements.

[0061] In summary, the combination of a CBRN barrier layer 58 which is resistant to the permeation of hazardous agents and a resilient layer 60 which is resiliently deformable, provides a diaphragm 18 which is resistant to the permeation of hazardous agents and is suitably sensitive to differential pressure changes.

[0062] The diaphragm 18 described above is of a similar size and shape to that of certain conventional diaphragms, i.e. those that are not CBRN compliant. This allows a standard LDV to be upgraded and retrofitted with a CBRN compliant diaphragm 18, such as that described above.

[0063] The LDV 10 incorporating the diaphragm 18 is compact and relatively simple to manufacture. Further, the face-mask to which the LDV 10 is attached, does not have to be modified so that it can be used with the LDV 10.

[0064] As outlined above, although it has been described that the LDV 10 incorporating the diaphragm 18 complies with particular LDV and CBRN-specific requirements, it should be appreciated that the LDV 10 incorporating the diaphragm 18, or the diaphragm 18 itself, may comply with other requirements instead or in addition.

[0065] Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention. This disclosure is intended to cover any adaptations or variations of the embodiments discussed herein

[0066] Attachment A

Statement of Standard

[0067] The SCBAs must meet the following minimum requirements: [0068] Approval under NIOSH 42 CFR Part 84, Subpart H [0069] Compliance with National Fire Protection Association (NFPA) Standard 1981 for Open-Circuit Self-Contained Breathing Apparatus for Fire Fighters [0070] Special Tests under NIOSH 42 CFR 84.63(c) [0071] (1) Chemical Agent Permeation and Penetration Resistance Against Distilled Sulfur Mustard (HD) and Sarin (GB) [0072] (2) Laboratory Respirator Protect on Level (LRPL) [0073] (1). Chemical Agent Permeation and Penetration Resistance Against Distilled Mustard (HD) and Sarin (GB) Agent Test Requirement [0074] Open-circuit, positive-pressure SCBAs, including all components and accessories except the air cylinder (shell), shall resist the permeation and penetration of distilled sulfur mustard (HD) and sarin (GB) chemical agents when tested on an upper-torso manikin connected to a breathing machine operating at an air flow rate of 40 liters per minute (L/min), 36 respirations per minute, 1.1 liters tidal volume.

[0075] Test requirements for distilled sulfur mustard (HD) are shown in Table 1.

TABLE-US-00001 TABLE 1 Simultaneous Liquid and Vapor Challenge of SCBA with Distilled Sulfur Mustard (HD) Maximum Breakthrough Breathing (concentration Duration Machine Maximum integrated Number Minimum of Airflow Peak over Minimum of Service Challenge Challenge Rate Excursion Service Life) Systems Life Agent Concentration (min) (L/min) (mg/m.sup.3) (mg-min/m.sup.3) Tested (hours) HD-Vapor 300 mg/m.sup.3 30.sup.(1) 40 0.60.sup.(3) 6.0.sup.(4) 3 6.sup.(2) HD-Liquid 0.86 ml 360 .sup.(1)Vapor challenge concentration will start immediately after the liquid drops have been applied and the test chamber has been sealed. .sup.(2)The test period begins upon start of initial vapor generation. .sup.(3)Three consecutive sequential test data points at or exceeding 0.6 mg/m.sup.3 will collectively constitute a failure where each test value is based on a detector sample time of approximately 2 minutes .sup.(4)The cumulative Ct including all peak data points must not be exceeded for the duration of the 6-hour test.

[0076] Test requirements for sarin (GB) agent are shown in Table 2.

TABLE-US-00002 TABLE 2 Vapor Challenge of SCBA with Sarin (GB) Maximum Breakthrough Breathing (concentration Vapor Machine integrated over Number Vapor Challenge Airflow Maximum Peak Minimum of Minimum Challenge Concentration Time Rate Excursion Service Life) Systems Service Life Agent (mg/m.sup.3) (minutes) (L/min) mg/m.sup.3 (mg-min/m.sup.3) Tested (hours) GB 2,000 mg/m.sup.3 30.sup.(1) 40 0.087.sup.(3) 2.1.sup.(4) 3 6.sup.(2) .sup.(1)The vapor challenge concentration generation will be initiated immediately after test chamber has been sealed. .sup.(2)The test period begins upon initial generation of vapor concentration. .sup.(3)Three consecutive sequential test data points at or exceeding 0.087 mg/m.sup.3 will collectively constitute a failure where each test value is based on a detector sample time of approximately 2 minutes. .sup.(4)The cumulative Ct including all peak data points must not be exceeded for the duration of the 6-hour test. [0077] (2). Laboratory Respiratory Protection Level (LRPL) Test Requirement [0078] The measured laboratory respiratory protection level (LRPL) for each open-circuit positive-pressure self-contained breathing apparatus shall be when the 500 facepiece is tested in a negative pressure mode in an atmosphere containing 20-40 mg/m.sup.3 corn oil aerosol of a mass median aerodynamic diameter of 0.4 to 0.6 micrometers.