EP1732804B1

EP1732804B1 - Second exhaust valve for a second stage regulator

Info

Publication number: EP1732804B1
Application number: EP05724144A
Authority: EP
Inventors: Sergio A. Angelini
Original assignee: Johnson Outdoors Inc
Current assignee: Johnson Outdoors Inc
Priority date: 2004-02-26
Filing date: 2005-02-28
Publication date: 2008-04-30
Anticipated expiration: 2025-02-28
Also published as: DE602005006400T2; DE602005006400D1; WO2005082706A1; ATE393727T1; EP1732804A1; US20050189019A1

Abstract

A second stage regulator and a method providing a second stage regulator that is adapted for use in both warm and cold water conditions are disclosed. The second stage regulator includes a base, a first exhaust and a second exhaust that is adapted to be removably coupled to the base so that the second exhaust valve is positioned in series with the first exhaust valve. The method comprises providing a second stage regulator base module and a second exhaust valve module, wherein the second stage regulator base module includes a first exhaust valve and the second exhaust valve module includes a second exhaust valve. The method also comprises removably coupling the second exhaust valve module to the second stage regulator base module, and configuring the second stage regulator base module to be functional without having the second exhaust valve module coupled to the second stage regulator base module.

Description

FIELD OF THE INVENTION

The present invention relates to an underwater diving second stage regulator configuration that minimizes icing of the regulator when in cold water. More particularly, the present invention relates to a second exhaust valve that may be selectively added-on to a second stage regulator when in cold water to prevent water droplets from entering the second stage regulator through a first exhaust valve of the second stage regulator.

BACKGROUND OF THE INVENTION

Second stage regulators, such as those used in underwater diving, are generally known in the art. Typically, second stage regulators, also known as breathing regulators, constitute the second of two stages of gas pressure regulation between a pressurized air source (e.g. one or more tanks of compressed gas) and the respiratory system of a user. As conventionally known, a first stage regulator is operatively connected to the pressurized air source and delivers gas at an intermediate pressure to the second stage regulator. A function of a second stage regulator is to then deliver the gas to the user at a breathable pressure in response to inhalation by the user.
When the user inhales, gas flows from the pressurized air source through the first stage regulator resulting in a first expansion of the gas flow. After the gas exits the first stage regulator, the gas flows through the second stage regulator resulting in a second expansion of the gas flow. Each expansion causes a lowering of the temperature of the gas itself. Since the initial temperature of the gas is the ambient temperature, and the decrease in temperature resulting from the expansion starts at this temperature, the lower the ambient temperature the lower the final temperature of the gas in the second stage regulator. It is possible for the gas flow flowing through the second stage regulator to be at a temperature well below that at which water freezes.
It is generally known that second stage regulators must have an opening in direct communication with the ambient water for the removal of exhaled gas. Conventional second stage regulators tend to have a single interface overlying the opening. The interface functions as one-way valve to allow the exhaled gas to exit the second stage regulator without allowing the ambient water from entering the second stage regulator. However, in operation, water droplets are likely to slip past the interface and enter the second stage regulator. Turbulence within the regulator may cause the water droplets to come into contact with components of the second stage regulator (i.e. levers, springs, valves, etc.).
if water droplets are present in a supercooled second stage regulator the water droplets may condense and freeze on the supercooled components of the regulator causing icing within the regulator housing. Icing can continue to build up to the point where it can prevent the proper movement of the components of the second stage regulator. Preventing the proper movement of the components of the second stage regulator may adversely affect the performance of the second stage regulator. Further, restricting proper movement of the components may lead to premature depletion of the user's air supply.
Accordingly, it would be advantageous to provide a second stage regulator system which reduces the formation of ice on components of the second stage regulator when the second stage regulator is being used in cold ambient water. It would further be desirable to provide a second stage regulator system that prevents water droplets from entering the second stage regulator through the interface overlying the exhaust opening in a conventional second stage regulator. It would further be advantageous to provide a second stage regulator system that utilizes two interfaces between the ambient water and the components of the second stage regulator. It would further be advantageous to provide one second stage regulator system that could be used safely in both warm and cold ambient water. It would further be advantageous to provide a second stage regulator system that is modular so that the second interface can be selectively added or removed from the first interface.
Patent US-A-2758596 discloses a portable breathing apparatus for a diver, which includes a main exhalation valve for venting exhaled air from the breathing chamber into the ambient medium. The casing of the main exhalation valve extends outwards and is threaded to receive a threaded cover. Between the cover and the outer end of the casing is clamped the outer end of a cup-shaped, flexible, control exhalation valve. However, there is no suggestion that this apparatus is modular, or that it can be used without the control exhalation valve.

SUMMARY OF THE INVENTION

The present invention provides a secondary valve module as defined in claim 1.
The present invention further provides a second stage regulator including such a secondary valve module, as defined in claim 3.
The present invention further relates to method of providing a second stage regulator that is adapted for use in both warm and cold water conditions, as defined in claim 15.
Preferred features of the invention are defined in the dependent claims.
The present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. Other ways in which the objects and features of the disclosed embodiments are accomplished will be described in the following specification or will become apparent to those skilled in the art after they read this specification. Such other ways are deemed to fall within the scope of the disclosed embodiments if they fall within the scope of the claims which follow.

DESCRIPTION OF THE FIGURES

FIGURE 1 is a perspective view of a modular second stage regulator system including a second stage regulator base module and a secondary exhaust valve module.
FIGURE 2 is an exploded view of the modular second stage regulator system of FIGURE 1.
FIGURES 3A through 3D are a cross-sectional view of the modular second stage regulator system illustrating a typical breathing cycle.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EXEMPLARY EMBODIMENTS

Before proceeding to the detailed description of a preferred and exemplary embodiments, it is to be understood that the invention is not limited to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of mating with the first module interface of the second stage regulator base module to provide releasable coupling of the second exhaust valve in series with the first exhaust valve.
The present invention further relates to various features and combinations of features shown and described in the disclosed embodiments. Other ways in which the objects and features of the disclosed embodiments are accomplished will be described in the following specification or will become apparent to those skilled in the art after they read this specification. Such other ways are deemed to fall within the scope of the disclosed embodiments if they fall within the scope of the claims which follow.

DESCRIPTION OF THE FIGURES

DETAILED DESCRIPTION OF PREFERRED AND OTHER EXEMPLARY EMBODIMENTS

Before proceeding to the detailed description of a preferred and exemplary embodiments, it is to be understood that the invention is not limited to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or being practiced or carried out in various ways. It is also to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
Referring to FiGURE 1, a modular second stage regulator system 10 is shown according to a preferred embodiment. While the disclosed embodiments will be illustrated as a second stage regulator designed for underwater diving, the features of the disclosed embodiments have a much wider applicability. For example, the modular second stage regulator system is adaptable for any air regulating application sensitive to icing of the second stage regulator due to moisture in the ambient environment entering the second stage regulator through an exhaust opening (e.g. divers in coldwater conditions, firefighters working in a cold environment in which there is moisture in the air, etc.). Modular second stage regulator system 10 comprises a second stage regulator base module 12 and an added-on secondary exhaust valve module 60.
Secondary exhaust valve module 60 is an add-on module that may be selectively added or removed from modular second stage regulator system 10. According to a preferred embodiment, secondary exhaust valve module 60 is releasable coupled (e.g. added-on, attached, mounted, connected, etc.) to second stage regulator base module 12. The ambient water dictates whether secondary exhaust valve module 60 should be coupled to or removed from second stage regulator system 10. It should be noted that second stage regulator base module 12 is operational without secondary exhaust valve module 60, and in certain circumstances it would be desirable to use second stage regulator base module 12 by itself. As best shown in FIGURE 2, second stage regulator base module 12 generally includes a housing 14, an inlet 16, a typical valve assembly (not shown), a regulator chamber 18, a mouthpiece 20, a primary exhaust valve mechanism 22, and a modular interface 24.
Housing 14 is generally rigid and has an interior that defines regulator chamber 18. Regulator chamber 18 is configured to communicate with the pressurized air source (not shown) through inlet 16. A typical valve assembly (not shown) within second stage regulator base module 12 comprises several components (e.g. a demand lever, a biasing member, sealing members, etc) and delivers the pressurized air source to the user at a breathable pressure. Regulator chamber 18 further communicates with the respiratory system of the user through mouthpiece 20. In addition, regulator chamber 18 is in direct communication with the ambient water through an opening 26 in housing 14. Direct communication exists between regulator chamber 18 and the ambient water because of the need to expel gases exhaled by the user. The interface between regulator chamber 18 and the ambient water is primary exhaust valve mechanism22. Primary exhaust valve mechanism 22 is a one-way valve for enabling exhaled air from the user to escape from regulator chamber 18 without permitting the ambient water to enter second stage regulator base module 12.
According to a preferred embodiment, primary exhaust valve mechanism 22 comprises a flapper valve 28 overlying a support member, shown as an exhaust spider 30. In the closed position, flapper valve 28 provides a seal between the ambient environment and regulator chamber 18. Exhaust spider 30 provides a means for supporting the flapper valve 28 while also permitting exhaled gas to flow through the support member. According to a preferred embodiment, exhaust spider 30 has a hub and spoke configuration for allowing exhaled gas to pass through support openings 32 located between the spokes. Preferably flapper valve 28 includes a valve stem 34 so that when flapper valve 28 overlies exhaust spider 30, valve stem 34 engages with the hub of exhaust spider 30 to provide for longitudinal movement of valve 28.
As can be appreciated, support for flapper valve 28 may be provided by one of a variety of configurations that provide support to a flapper valve while also allowing gas to pass through the support (e.g. a web-like configuration, an open weave configuration, etc.). In addition, primary exhaust valve mechanism 22 is not limited to a flapper valve and support member configuration, but may comprises any one-way valve configuration (i.e. a check valve, a curtain valve or the like, etc.).
According to a preferred embodiment, exhaust spider 30 covers opening 26 and is integrally formed with housing 14 as a single unitary body. Alternatively, exhaust spider 30 may be a separate component coupled to housing 14. Coupling exhaust spider 30 to housing 14 may be achieved through any of a variety of configurations (e.g. press fit, snap fit, locking tabs, mechanical fasteners (e.g. screws, bolts, rivets, pins, etc.), etc.). Alternatively, exhaust spider 30 may be fused to housing 14 as a single molded unit (e.g., welding, ultrasonic, adhesives, etc.).
During a typical breathing cycle of the user, exhaled gas passes outwardly through support openings 32 of exhaust spider 30 and radially outwardly between flapper valve 28 and the perimeter of exhaust spider 30. The pressure increase within regulator chamber 18 lifts flapper valve 28 in the longitudinal direction allowing the gas to exit. When the user stops exhaling flapper valve 28 closes and reestablishes the seal between the ambient water and regulator chamber 18 to prevent water from entering second stage regulator base module 12.
Ideally, primary exhaust valve mechanism 22 allows the exhaled gas to exit regulator chamber 18 without permitting the ambient water from entering second stage regulator base module 12. However, the introduction of water droplets through primary exhaust valve mechanism 22 is not entirely avoidable. For example, as flapper valve 28 closes at the end of exhalation, water droplets may slip through before flapper valve 28 seals completely to exhaust spider 30. In addition, inhalation by the user through mouthpiece 20 causes a pressure drop within regulator chamber 18. A strong or sudden inhalation may initiate a turbulent flow that may cause flapper valve 28 to flutter. Such fluttering of flapper valve 28 is likely to cause uneven opening and closing of flapper valve 28 which may allow water droplets to slip past flapper valve 28.
When modular second stage regulator system 10 is used in warm water (i.e. water at a temperature for which there is no concern about regulator malfunction due to supercooling of the regulator), the ambient water and the gas passing through the system will prevent regulator supercooling, and the introduction of water through primary exhaust valve mechanism 22 will not lead to icing of second stage regulator base module 12. Therefore, in warm water, modular second stage regulator system 10 may be selectively used without secondary exhaust valve module 60.
In warm water (e.g. water having a temperature above approximately 10 degrees Celsius), when the user inhales through mouthpiece 20, a rapid pressure drop and expansion of gas occurs within second stage regulator base module 12. The rapid pressure drop and expansion of gas causes a cooling condition within second stage regulator base module 12. Since the surrounding water is warm, the heat from the water warms second stage regulator 12 and regulator supercooling is avoided. If warm water droplets enter second stage regulator base module 12 through primary exhaust valve mechanism 22, the warm water droplets will not cause icing within the regulator or around flapper valve 28, and will likely be flushed out of second stage regulator base module 12 through primary exhaust valve mechanism 22 upon a subsequent exhalation by the user.
If modular second stage regulator system 10 is going to be used in cold water (e.g. water having a temperature below approximately 10 degrees Celsius), the ambient water may sustain the supercooling of second stage regulator base module 12. Because the ambient water is cold, there is no ambient heat to dampen the cooling condition occurring within second stage regulator base module 12. Further, the likelihood of achieving the supercooled condition is worsened by the fact that the gas starts at a lower temperature when the system is used in cold water. If second stage regulator base module 12 becomes supercooled, the introduction of cold water droplets to second stage regulator base module 12 through primary exhaust valve mechanism 22 may lead to icing and subsequently regulator malfunction. Malfunction may result from a cold water droplet freezing around flapper valve 28, which may lead to imperfect sealing of flapper valve 28 to exhaust spider 30. An imperfect seal allows for additional cold water to enter second stage regulator base module 12. Alternatively, turbulence within second stage regulator base module 12 may displace a cold water droplet near the components of the valve assembly (not shown) within second stage regulator base module 12. If a cold water droplet freezes near a component, the icing can impair the operation of second stage regulator base module 12.
To prevent the introduction of cold water droplets into second stage regulator base module 12 through primary exhaust valve mechanism 22, secondary exhaust valve module 60 is coupled to second stage regulator base module 12. Referring to FIGURE 2, secondary exhaust valve module 60 is coupled by detachably mounting secondary exhaust module 60 in series with primary exhaust valve 22. To enable modularity between second stage regulator base module 12 and secondary exhaust valve module 60, second stage regulator base module 12 further includes module interface 24. Module interface 24 is configured for mating with the corresponding module interface of secondary exhaust valve module 60. According to a preferred embodiment, module interface 24 is threaded. Alternatively, the mating of module interface 24 and the corresponding module interface of secondary exhaust valve module 60 may be provided by one of a variety of other mating mechanisms that provide for releasable mating (e.g. press-fit, snap-fit, locking tabs, etc.).
According to a preferred embodiment, secondary exhaust valve module 60 is sealably coupled to second stage regulator base module 12. A seal positioned between secondary exhaust valve module 60 and second stage regulator base module 12 advantageously prevents water droplets from entering the system at the point of coupling. According to a particularly preferred embodiment, an O-ring 78 positioned near interface 24 provides a substantially watertight seal. In alternative embodiments, any appropriate means can be used to provide a substantially watertight seal between secondary exhaust valve module 60 and second stage regulator base module 12 (e.g. press-fit, taping of threads, gaskets, etc.) as long as it will serve the purpose discussed above.
Referring to FIGURE 2, secondary exhaust valve module 60 generally comprises a secondary exhaust valve mechanism 62 and a module interface 68. According to a preferred embodiment, secondary exhaust valve moduie 60 further comprises a body 64 and an exhaust chamber 66. Alternatively, body 64 and exhaust chamber 66 may be integrally formed as part of second stage regulator base module 12. According to a preferred embodiment, body 64 is a generally rigid housing comprising a first end 70 and second opposite end 72. Body 64 has an interior defining exhaust chamber 66 which extends from first end 70 to second end 72. First end 70 includes module interface 68 for mating with module interface 24 of second stage regulator base module 12. According to an exemplary embodiment, shown in FIGURE 2, module interface 68 is integrally formed as part of body 64. Alternatively, if body 64 is integrally formed as part of second stage regulator base module 12, module interface 68 may be integrally formed as part of secondary exhaust valve mechanism 62. According to the preferred embodiment, module interface 68 is threaded for releasably mating with the threads of module interface 24 of second stage regulator base module 12. The mating of module interface 68 and module interface 24 forms a seal between second stage regulator base module 12 and secondary exhaust valve module 60. Alternatively, the mating of module interface 68 to module interface 24 may be provided by one of a variety of other mating mechanisms that provide for releasable mating and a seal (e.g. press-fit, snap-fit, locking tabs, gaskets, etc.).
Secondary exhaust valve mechanism 62 is a one-way valve for enabling exhaled gas from the user to escape second stage regulator base module 12. Secondary exhaust valve mechanism 62 is coupled to second end 72 of body 64 and generally includes a secondary exhaust spider 74 and secondary flapper valve 76. The configuration and operation of secondary exhaust valve mechanism 62 is substantially similar to the configuration and operation of primary exhaust valve mechanism 22. As illustrated in FIGURE 2, secondary exhaust valve mechanism 62 is a separate component coupled to second end 72 of body 64. As can be appreciated, coupling may be accomplished by any of a variety of conventional or appropriate ways including, but not limited to, fusing, adhesive, mechanical fasteners (e.g. bolts, screws, rivets, etc.), press-fit, etc. Alternatively, secondary exhaust valve mechanism 62 and body 64 may be integrally formed as a single unitary body.
Exhaust chamber 66 is a dry chamber with first end 70 in communication with regulator chamber 18 and second end 72 in communication with the ambient water. Exhaust chamber 66 is adequately dimensioned in the longitudinal direction to provide sufficient clearance for the unrestricted operation of primary exhaust valve mechanism 22 and secondary exhaust valve mechanism 62.
FIGURES 3A through 3D illustrate a typical breathing cycle of the user using second stage regulator base module 12 selectively fitted with secondary exhaust valve module 60. When the user first inhales through mouthpiece 20, both primary exhaust valve mechanism 22 and secondary exhaust valve mechanism 62 are in a closed position. Upon exhalation, the pressure within regulator chamber 18 increases and the exhaled gas passes outwardly through support openings 32 of exhaust spider 30. The increased pressure first causes primary exhaust valve mechanism 22 to open while secondary exhaust valve mechanism 62 remains closed. The exhaled gas enters exhaust chamber 66 and flows towards second end 72 of body 64. As the pressure within exhaust chamber chamber 66 increases, secondary exhaust valve mechanism opens and enables the exhaled gas to exit second stage regulator system 10.
Once exhalation stops, the pressure within regulator chamber 18 begins to drop. The pressure decrease is first realized by primacy exhaust valve mechanism 22 and causes primary exhaust valve mechanism 22 to close while secondary exhaust valve mechanism 62 remains open. At this stage, second stage regulator base module 12 is sealed off from the ambient water, while secondary exhaust valve mechanism 62 remains in direct fluid communication with the ambient water. Eventually, secondary exhaust valve mechanism realizes the drop in pressure and subsequently closes.
Generally, during operation, no ambient water is present in exhaust chamber'66. However, if water droplets slip past secondary exhaust valve mechanism 62 upon closing water droplets may enter exhaust chamber 66. Any water droplets bypassing secondary exhaust valve mechanism 62 will be confined to exhaust chamber 66 and will not enter second stage regulator base module 12 since primary exhaust valve mechanism 22 is already in the closed position. Therefore, any water droplets bypassing secondary exhaust valve mechanism 62 will not reach the components of second stage regulator base module 12 and will not cause icing within the regulator. In addition, icing around secondary flapper valve 76 is unlikely since secondary flapper valve 76 is not directly exposed to the cooling condition occurring within second stage regulator base module 12. Also, it is unlikely that water droplets would freeze within exhaust chamber 66 since exhaust chamber 66 is also not directly exposed to cooling condition occurring within second stage regulator base module 12. Any water droplets confined to exhaust chamber 66 will likely be flushed from modular second stage regulator system 10 on the subsequent exhalation of the user.
The addition of secondary exhaust valve module 60 to second stage regulator base module 12 does have an adverse consequence which is why the configuration is modular. By selectively adding-on secondary exhaust valve module 60 to second stage regulator base module 12, the user must now exert more pressure (i.e. exhale harder) to remove exhaled gas from modular second stage regulator system 10. More pressure is necessary to remove the exhaled gas since the force necessary to open two exhaust valves is greater than the force necessary to open one exhaust valve. Therefore, in accordance with the present invention, the system is designed to be modular. Modularity permits a user to easily add secondary exhaust valve module 60 to second stage regulator base module 12 when needed to help prevent regulator malfunction, and remove secondary exhaust valve module 60 when not needed. Secondary exhaust valve module 60 may be added or removed from second stage regulator base module 12 before the user is going to operate second stage regulator system 10.
Alternatively, secondary exhaust valve module 60 may be added or removed from second stage regulator base module 12 by the user during operation of second stage regulator system 10. The configuration of module interface 24 and module interface 68 is designed so that secondary exhaust valve module 60 can be easily added or removed from second stage regulator base module 12.
It is also important to note that the construction, arrangement, and application of the modular second stage regulator system as shown in a preferred and other exemplary embodiments are illustrative only. Although only a few embodiments of the present invention have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., compatibility with alternative applications, variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the appended claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and/or omissions may be made in the design, operating conditions and arrangement of a preferred and other exemplary embodiments without departing from the scope of the present invention as expressed in the appended claims.

Claims

A secondary valve module (60) for use with a second stage regulator (10) having a first exhaust valve (22) and a first interface (24), the secondary valve module (60) comprising:
a second exhaust valve (62); and

a second interface (68) adapted to detachably engage the first interface (24) in a manner that positions the second exhaust valve (62) in series with the first exhaust valve (22);
characterized in that the second exhaust valve (62) includes a flapper valve (76) and an open support member (74).
The secondary valve module (60) of Claim 1 wherein the open support member (74) is an exhaust spider having a hub and spoke configuration adapted to support the flapper valve (76) while allowing exhaled gas to pass through the exhaust spider.
A second stage regulator for use with a pressurized air source and a first stage regulator, the second stage regulator (10) comprising:
a base (12) having a housing (14), a first exhaust valve (22) and a first interface (24); and

a secondary valve module (60) as defined in Claim 1 or Claim 2.
The second stage regulator of Claim 3 wherein a user may optionally operate the base (12) without the secondary valve module (60).
The second stage regulator of Claim 4 wherein the first exhaust valve (22) includes a flapper valve (28) and an open support member (30).
The second stage regulator of Claim 5 wherein the open support member (30) of the first exhaust valve (22) is an exhaust spider having a hub and spoke configuration adapted to support the flapper valve (28) while allowing exhaled gas to pass through the exhaust spider.
The second stage regulator of any of Claims 3 to 6 wherein the secondary valve module (60) further includes a body (64) defining an exhaust chamber (66) having a first end (70) and a second opposite end (72).
The second stage regulator of Claim 7 wherein the second interface (68) is located at the first end (70) of the exhaust chamber (66) and the open support member (74) is coupled to the second end (72) of the exhaust chamber (66).
The second stage regulator of Claim 8 wherein the body (64) defining the exhaust chamber (66) is dimensioned so that the second exhaust valve (62) does not restrict the operation of the first exhaust valve (22).
The second stage regulator of Claim 9 wherein the exhaust chamber (66) is substantially a dry chamber including at least one seal (78) positioned near the second interface (68).
The second stage regulator of any of Claims 3 to 6 wherein the base (12) further includes a body defining an exhaust chamber having a first end and a second opposite end.
The second stage regulator of Claim 11 wherein the first end of the exhaust chamber is coupled near the first exhaust valve (22) and the first interface is located at the second end of the exhaust chamber for coupling to the secondary valve module (60).
The second stage regulator of Claim 12 wherein the body defining the exhaust chamber is dimensioned so that the second exhaust valve (62) does not restrict the operation of the first exhaust valve (22).
The second stage regulator of Claim 13 wherein the exhaust chamber is substantially a dry chamber including at least one seal positioned near the first interface.
A method of converting a second stage regulator (10) to be suitable for use in cold water conditions, the method comprising:
providing a base (12) that is operable in warm water conditions, the base (12) having a housing (14), a first exhaust valve (22) and a first interface (24);

providing a secondary valve module (60) having a second exhaust valve (62) and a second interface (68); and

removably coupling the secondary valve module (60) to the base (12) in a manner that the second interface (68) detachably engages the first interface (24) and the second exhaust valve (62) is positioned in series with the first exhaust valve (22).