GB2504778A - Automated gas pressure regulator - Google Patents

Abstract

An automated pressure regulator 60 includes an inlet port 72 configured to engage a pressurized gas bottle 58 to receive pressurized gas therefrom, and an outlet port 74 that may be sealably coupled to an inflatable bladder. The inlet port 72 is in fluid communication with the outlet port 74. The pressure regulator 60 further comprises a moveable check valve, such as a piston 64, disposed between the inlet port 72 and the outlet port 74. A gas seal 88 is engageable with an outer surface 90 of the check valve 64 and is configured so that, upon positive engagement by the check valve 64, the inlet 72 is isolated from the outlet 74. A spring 76 abuts the inner surface 80 of the check valve 64. The spring 76 positively biases the valve 64 against the seal 88 to selectively isolate the inlet port 72 and outlet port 74 when a predetermined closure pressure is exerted on an inner surface 80 of the check valve 64, by a combination of bias applied by the spring 76 and a gas pressure acting on the internal surface 80.

Description

Automated Gas Pressure Regulator & Inflatable Bladder System Incorporating Same

Field of the Invention

This invention relates, in general, to an automated gas pressure regulator and an inflatable bladder system and is particularly, but not exclusivdy, applicable to an automated and self-maintaining pressure tourniquet.

Summary of the Prior Art

A tourniquet is a constricting or compressing device used to control venous and arterial circulation to an extremity for a period of time. Pressure is applied circumferentially upon the skin and underlying tissues of a limb; this pressure is transferred to the walls of vessels, causing them to become temporarily occluded. Tourniquets aie generally used to stem the flow of traumatic bleeding, with speed of apphcation essential.

Severe bleeding means the loss of more than I000ml (one litre) of blood. This flow of blood can soak a paper or cloth handkerchief in a few seconds. Unless quickly abated, this rate of bleeding will cause the death of a casualty in seconds to minutes. In combat situations, the ability to attend to an injured soldier who is bleeding out through, for example, severe limb trauma is often impeded by virtual of the hostile environment and the ability of a colleague to get to the injured party and provide assistance.

Combat applied tourniquets have therefore been developed (see http://www,comhattourniuuet.co1Ttourniguet-videos.php), with these tourniquets conventionally making use of a double-backed distal end of the tourniquet threaded through and initially pulled tight through a buckle or plastic loop securely attached to the proximal end of the loop. Consequently, either the loop must be formed in advance of the tourniquet being placed over the limb and the limb/extremity eased through the loop, or the free end of the tourniquet must be threaded through the buckle in advance of the initial (manual) pull tightening phase. Only after the tourniquet has been located and pulled tight is a windlass rod used to increase applied circumferential pressure. Existing combat tourniquets therefore require intricate multi-stage application processes that waste valuable time. Indeed, to guarantee effective operation of existing combat tourniquets, the casually must be aided by another person.

In a different field of medical diagnosis, the tourniquet principle is adapted in the process of measuring arterial blood pressure with a sphygrnomanometer consisting of an inflatable cuff, a measuring unit (the mercury manometer, or aneroid gauge). and a mechanism for inflation which may be a manually operated bulb and valve or a pump operated electrically.

Pneumatic tourniquet cuffs are further frequently used for stopping arterial blood flow into a portion of a surgical patient's limb to facilitate the performance of a surgical procedure and for facilitating intravenous regional anesthesia. Typical toumiquet cuffs of the prior art include a sealed inflatable bladder that encircles the limb and communicates pneumatically with a connected tourniquet instrument through one or more cuff ports. a stiffener that helps direct the expansion of the bladder radially inwards towards the limb and helps prevent any twisting or rolling of the cuff on the limb, and one or more fasteners that secure the cuff around the limb.

Unfortunately, the bladders into which the air is pumped and sustained under pressure are constructed with a seam and/or made from a material that ultimately leaks. i.e. the bladder is not gas impermeable. In this respect, maintenance of an applied pressure of typically about Spsi (34.SkPa) to about 8psi (55.2kPa) is required to produce effective occlusion of the artery, so any leak (such as through a connector or the cuff/bladder material) in the portable system compromises the treatment/circulatory effects and needs to be identified and compensated. In any event, Limb Occlusion Pressure (LOP) varies according to which limb the toumiquet is applied and the patient's actual physiology.

From a medical perspective, the above tourniquet pressures effectively convert to a minimum effective tourniquet pressure (when applied to the thigh of a normotensive, non-obese patient) that is 90mm to 100mm of mercury (Hg) above systolic blood pressure. In an arm, a tourniquet pressure equivalent to 200mm Hg is frequently recommended.

However, in a battlefield environment, regular monitoring of the state of inflation of the cuff is not practical since pressure monitoring is neither accurate (given the portable nature of the tourniquet and its generally rapid deployment) nor particularly safe (given the environment) for the observer.

In contrast to portable units that must be small and lightweight, US 5,607.447 describes a static, large scale and complex physiological tourniquet, used in a hospital theatre environment, in which a computerized configuration register is incorporated into an electrically-powered tourniquet apparatus for enabling an operator to change the values of parameters initially employed at the time of the next use of the apparatus, such as the initial pressure settings and elapsed time limits.

In order to facilitate the attachment of fasteners and cuff ports. the manufacture of prior art cuffs having multiple ayers typically includes several labor-intensive operations, some of which require a high level of skill, quality and consistency on the part of manufacturing personnel. These operations can include sewing fastener materials to an outer cuff layer, adding a structural reinforcing patch to the outer layer, sealing one or more ports to a layer forming part of the inflatable bladder, and seating layers around a perimeter to form the bladder. Cuff layers consisting of compatible thermoplastic polymeric materials are typically joined together using a radio frequency (RF) welding process, which uses a combination of heat and pressure to cause compatible polymers to flow together by molecular diffusion. Gas passageways into the Nadder are typically formed using single or multiple ports welded to one layer before the bladder is formed.

Each port provides a gas passageway into the bladder through a reinforced structure that is attached to tubing extending outside the sterile surgical field for connection to a tourniquet instrument. Dunng the manufacturing process, the port is typically attached to one side of the bladder in a welding operation before the bladder is formed, to prevent the opposite Hadder surface from being wdded at the port location.

Many tourniquet cuffs of the prior art include a thermoplastic stiffener which helps direct the expansion of the cuff bladder radially inward toward the limb when pressurized and helps reduce any tendency of the cuff to twist when pressurized or to roll distally down a tapered limb. The absence of a stiffener can lead to a reduction of the efficient application of pressure to the limb and thus can lead to an increase in the level of pressure required to stop blood flow past the cuff and into the limb. Also, the absence of a stiffener can lead to additional stresses in the outer cuff surface due to less constrained bladder expansion. A second type of stiffener configuration involves increasing the thickness and rigidity of the material forming the outer cuff ayer to obtain a stiffening function from the outer layer in a two-layer cuff design. In this latter respect, exemplary reference is made to US 5,413,582-Eaton and in tourniquet cuffs distributed by Oak Medical, Briggs, North Lincs, UK. The outer layer of these prior art tourniquet cuffs serves both as a stiffener and as one side of the inflatable bladder. The thick outer layer extends to all of the cuff edges and includes an area for sealing the inner layer to the thick outer layer to form an inflatable bladder, resulting in the bladder always having a bladder width that is less than the width of the stiffener; this is undesirable because cuffs having narrower bladder widths require higher tourniquet pressures to stop blood flow, and higher tourniquet cuff pressures are associated with a higher risk of patient injury. A third stiffener configuration in tourniquet cuffs of the prior art includes an unsecured stiffener located within the inflatable bladder, e.g., as described by Goldstein et al. in US 5,411,518. In these configuration, the stiffener is unsecured within the bladder and does not constrain the expansion of the outer cuff surface.

Many cuffs of the prior art include velcro-type fastening elements, commonly referred to as hook and loop fasteners. The most common configuration consists of a hook-type fastening strap adapted for engaging with a loop-type material on the outer surface of the cuff to form a releasable velcro-type attachment when the cuff encircles a limb. hi US 5,201,758-Glover, a multi-layer tourniquet cuff has a bladder contained within a flexible covering and a backing plate and a fabric strap of loop-type material attached at one end to the outer side of the backing plate for releasably engaging with a strip of hook-type material peniianently mounted to the outer side of the backing plate. US 5,411,518-Goldstein describes a two-layer tourniquet cuff having a hook or loop fastening strap for engaging with an outer cuff surface of thop or hook material.

To help secure the end of the cuff in contact with the limb and to aid in cuff alignment during application, a number of cuffs in the prior art include a tie strap attached near one end of the cuff. Typica' cuffs which include a tie strap are described in US 6,682,547 and US 4.635,635. A tie strap allows a surgical user to achieve a snug application of the cuff to the limb, and when tied helps assure that the overlapping portion of the cuff remains aligned, thus helping to prevent twisting, telescoping and rolling of the cuff when inflated, and thus helping to assure the most effective transmission of pressure from the cuff to the limb.

lii general. it is desirable to construct the thinnest tourniquet cuff possible for a given appfication. Thinner cuffs have sma'ler differences in circumference between inner cuff surfaces and outer cuff surfaces when encircling a patient's limb, in comparison to thicker cuffs. Such smaller differences in circumference reduce folding and wrinkling at the inner cuff suiface. This reduces the possibility of wnnkling, pinching, bruising and other injuries to the skin and soft tissue encircled by such cuffs. Further, thinner cuffs tend to be less rigid than thicker cuffs and thus allow a surgical user to apply the cuff more snugly and more easily to the limb.

The manufacturing and assembly process of prior art cuffs consists of numerous cutting.

sewing, and sealing operations which require substantial investment in both equipment and skilled operators. The manual labor component of cuff assembly is high, especially where multiple sewing and sealing operations are required. It is therefore desirable to reduce the skill and time required by the cuff assembly process, while continuing to utilize readily available manufacturing equipment. A reduction in the amount of time and skill required to manufacture tourniquet cuffs can be accomplished by reducing the number of manual assembly operations. This may include the elimination of numerous sewing operations, and the consolidation of multiple RF sealing steps into a single operation. Reducing the number of manual operations provides a savings not only in the labor to construct a cuff, but also provides the potential for the automation of a number of steps leading to the single cuff sealing operation.

It is also known that self-inflating life vests, for example, can include a secondary one-way valve and tube that connect to allow supplementary inflation by exhalation of the wearer's breath into the tube and thus into an air pocket in the vest. The valve can be generally litfie more than a material flap that is forced open/closed by a rdative pressure differential across the valve.

In a more elaborate auto-inflating vest, a gas supply in a small bottle is sealably seated into a manifold and gasket of an inflator assembly. The gas bottle, containing a puncturable lid, is positioned adjacent a steel pierce pin or needle that is resistively held offset from the punchurable lid by a spring. A cam mechanism within the body of the inflator assembly attaches, at its distal end and via a lanyard, to a pull tab and lever. A proximal end of the cam is arranged to pivot into or otherwise move within the body of the inflation assembly to positively engage a head of the pierce pin upon deliberate and outward movement of the pull tab and lever. Consequently, the proximal end of the cam moves and this in turn moves the pierce pin laterally to cause the pierce pin to puncture the lid of the gas bottle to release compressed gas. The compressed gas then flows around the pierce pin and along a channel within the inflation assembly's body to expand into and inflate a bladder that is sealably coupled to an exhaust vent of the body. This alTangement is shown in FIG. 1, but will not be discussed further since this design and its operation are well known and commercial product has been available for many years.

GB 22789i i (Mackel) discloses an auto-inflator in which a pivoted cammed arm is capable of driving a puncture pin into a seal of a gas cylinder. The arm is held in repose by a torsion spring around the pivot, but is connected to a lanyard at the end of the arm.

Pulling the lanyard with sufficient force to overcome the torsion spring causes the arm to rotate and so to drive the pin into the gas container. The lanyard is also connected to a slideable member itself attached to a spring. The spring has a tendency to pull the slideable member, so operating the lanyard, but the slideable member is held in place by a retaining pin (transverse to the line of sliding). A soluble element holds the retaining pin in position, the soluble dement being firmly held against the retaining pin by a resilient member. The dissolution of the soluble element causes the pin to disengage from the slideahie member and so causes the inflation of the device.

Essentially, self-inflation devices, such as that described in Mackel, include the puncture pin and a communicating fluid path akng which gas from a reservoir is channeled to fill a bladder sealably connected thereto. In an altemative, a small detonator may be employed to breach or release the seal of the bas reservoir.

Summary of the Invention

In accordance with a first aspect of the invention there is provided an automated gas pressure regulator comprising: an inlet port configured, in use, to engage a pressurized gas bottle to receive pressurized gas therefrom; an outlet port in fluid communication with the outlet port; and a movable check valve disposed between the inlet port and the outlet port, the movable check valve having an inner surface and an outer surface; a gas seal engageable selectively by the outer surface of the check valve, the gas seal within the automated pressure regulator and configured such that, upon positive engagement by the check valve the inlet is isolated from the outlet port; and a spring abutting against the inner surface to positively bias the check va've against the seal autornaticafly to regulate closure of the check valve and selectively to isolate the inlet port from the outlet port when a predetermined dosure pressure is exerted on the inner surface of the check valve by a combination of the bias applied by the spring and a gas pressure acting on said i nterna surface.

Tn a second aspect of the present invention there is provided a portable rapid inflation system comprising: an inflatable gas bladder; and an automated gas pressure regulator according to any preceding claim, the gas pressure regubtor sealably coupled to the inflatable gas bladder; and a pressunzed gas bottle coupled to the inlet port; wherein the automated gas pressure regulator is configured to control and substantially maintain inflation of the bladder at an inflation level having a predetermined internal pressure and wherein disengagement of the movable check valve relative to the seal occurs when a gas pressure (Pr) in the portable gas bottle is greater than a combination of an opposing intema gas pressure (Pt) within the gas bladder and the bias exerted by the spring.

Advantageously, the spring's tension is selected or varied to moderate the point when pressunzed gas in the gas bottle overcomes the closure force and determines (and maintains) the level of inflation of the bladder. The automated regulator finds application in devices where rapid inflation is important and where, post inflation, monitoring of the pressure in the internal bladder is desiraHe so as to maintain an acceptable (minimum) pressure, but where user observation is not necessarily practicable because of the sulTounding environmental conditions. The pressure regulator can be integrated into a portable battlefield tourniquet or a life vest where the user needs to concentrate on potentially more significant real-time events that may affect their security or survival.

The preferred embodiment of the invention therefore provides a low-cost and effective pressure regulator that automatically maintains a predetermined level of inflation in a substantially gas impermeaNe inflation Hadder.

Brief Descnption of the Drawings Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 is a representation of a prior art inflator assembly; FIG. 2 is a representation of a tourniquet of a preferred embodiment of the present invention; FIG. 3 is a schematic representation of a pressure regulator incorporated into a inflation assembly of FIG. 2; FIG. 4 is an alternative configuration for a moveable diaphragm employed within the pressure regulator of FIG. 3.

Detailed Description of a PrefelTed Embodiment

A preferred embodiment of the invention pertains to pneumatic tourniquet cuffs commonly used for stopping arterial blood flow into a portion of a surgical patient's limb to arrest blood flow or facilitate the performance of a surgical procedure, and for facilitating intravenous regional anesthesia. h this respect, one or more of the aforementioned prior art methods of construction of the cuffs made be empthyed to produce an effective bladder and cuff configuration. Similarly. the process of fixing or otherwise mounting an inflation valve (such as generally described in Mackel and in products of Halkey-Roberts, including the PRO 3F® MANUAL INFLATOR) to such a cuff are well known to the skilled addressee so further explanation is avoided for reasons of brevity only. However, the functionality and configuration of the inflation valve is inventiv&y modified in the present invention to provide an improved automated pressure maintenance valve and rapid inflation system.

The invention in particular relates to inflatable devices wherein a gas charging device (fed from a reservoir) is capable of inflating or expanding one or more bladders and especially to inflatable devices that require a specific internal pressure to function and means to maintain that pressure. The term "bladder" should however be interpreted broadly to cover any fluid inflatable pouch that is charged from an external portable reservoir, with the fabric of the bladder constructed from a material fit for purpose, e.g. a substantially gas impermeable membrane or fabric that is effectively in sealed contact with an automated pressure maintenance valve of a preferred embodiment.

Before discussing the present invention, brief reference is made to the auto-inflating life vest 10. A gas supply in a small bottle (not shown) is sealably seated into a manifold and gasket 12 of an inflator assembly 13 attached to a bladder 14. The gas bottle, containing a puncturable lid, is positioned adjacent a steel pierce pin or needle 16 that is resistively held offset from the punchurable lid by a spring 18. A cam mechanism 20 within the body of the inflator assembly attaches, at its distal end and via a lanyard 22, to a pull tab and lever 24. A proximal end of the cam is arranged to pivot into or otherwise move within the body of the inflation assembly to positively engage a head of the pierce pin upon deliberate and outward movement of the put! tab and lever. Consequendy, the proximal end of the cam moves and this in turn moves the pierce pin laterally to cause the pierce pin to puncture the lid of the gas bottle to release compressed gas. The compressed gas then flows around the pierce pin and along a channel within the inflation assembly's body to expand into and inflate the bladder 14 that is sealably coupled to an exhaust vent of the body. Since in the context of buoyant, one requires full inflation immediatdy, the puncturing of the gas lid releases all the gas to ensure full inflation and positive buoyance not matter the size of the wearer of the life preserver/vest, Further expbnation is not considered necessary since this design and its operation are well known and commercial product has been available for many years.

The inventor has identified as key the fact that, with portable gas-discharge inflation systems, there is some excess gas within the supply reservoir after inflation of the bladder. Furthermore, in the context of a battlefield tourniquet, it is unwise if not dangerous to apply excessive arterial occlusion pressures, but conversely sufficient pressure must be exerted and maintained to stern the flow of blood at all times (even though the system have inherent leak issues).

lii the exemplary context of the a preferred configuration of a tourniquet 40 shown in FIG. 2, then tourniquet 40 includes a cuff 42 containing an internal bladder 44 that is inflated through an inflation assembly 46 of a preferred embodiment. The inflation assembly 46 is coupled to a pressurized gas reservoir 48, such as a "sparklets" bulb containing compressed CO2. The cuff, which may be multi-layer. typically has a fabric surface 50 upon. A fastening mechanism made up of complementary Velcro hooks and loops is disposed on the fabric surface and, typically, an end rap. Other forms of fastener () may be employed, as will readily be appreciated, but Velcro presents a rapid and easy to use arrangement. Optionally, a hose 52 may be in fluid communication with the internal bladder 44 through a one-way valve 54, with the hose attached to a bulb pump 56 that can provide for a redundant inflation mechanism that supplements the inflation assembly 46. The hose and bulb pump are preferably detachable.

Referring to FIG. 3 there is shown a preferred embodiment for an automatic pressure regulator 60 incorporated into the inflation assemNy 46 of FIG. 2. The pressure regulator 60 includes a moveable piston 62 which, by way of exemplary configuration only, is in the general form of an element having a T-shaped section. The element may comprise a rigid central stem 64 that, at a first end 66, includes a radially extending flange 68. The moveable piston 62 is located within a chamber 70 that includes an inlet port 72 and an outlet port 74. A steel spring 76 is recessed within the chamber 70 cooperates with the moveable piston 62 such to resist backward movement of the piston relative to the inlet port. For example, the spring may locate against a rear internal wall 82 of the chamber and abut against an inner surface 80 of the radially extending flange 68. Other location points for the spring are feasible. Indeed, more than one spnng can be used, although it is preferred for the spring 76 to be coiled around the central stem 64. A seal 88, such as an 0-ring gas impermeable gasket, is located in a front inside edge of the chamber 70 such that the seal 88 can engage against an outer surface 90 of the radially extending flange 68. The outlet port 74 is sealed, in use, to the inflatable bladder 44 (shown in FIG. 2).

Functionally, the piston 62 is therefore able to move into contact with or away from the seal 88, with movement away from contact being resisted (at least in part) by the action of the spring 76. The piston's movement is preferably constrained to a linear movement.

e.g. through the use of guide that partially sunounds the stern 64.

The inlet port 72 allows attachment of a pressunzed gas canister or bottle 48 to the inflation assembly 46. For example, the inlet port may include a thread 92 that is complementary to a thread 94 on the gas bottle. Once the threads are engaged and the gas bottle wound onto the inflation assemNy, a seal of the gas bottle is temporarily disrupted and relatively high pressure gas (such as CO2 at 120 psi (827.4kPa)) acts upon a relatively small area on the outer surface 80 of the radially extending flange 68.

The gas pressure in the gas cy'inder Pr, provided it overcomes a combination of an opposing internal gas pressure P and the force exerted by the spring 76, forces the piston backwards from the inlet port 72 and thus causes the outer surface 90 of the piston 64 to disengage from the seal 88. Gas expands rapidly into the bladder by flowing around the radially extending flange 68 until such time as the combined internal pressure (within the bladder) in cornbination with the tension in the spring force the piston forward to cause sealing engagement of the radially extending flange 68 against the seal 88.

The tension of the spring Sc is therefore set to produce a certain predetermined amount of internal pressure that, in the case of a tourniquet, is sufficient to produce arterial occlusion.

Expressly this as a basic mathematical formula, the piston is closed so long as with P+S providing an internal bladder pressure that achieves a desired inflation, level of buoyancy, etc. (preferably with an additional safety factor). Closure of the piston against the seal may therefore occur at an internal pressure of, for example, between about 7psi and lOpsi (pounds per square inch), with this internal pressure achieved by gas acting over a relatively large surface of the inner surface 80 of the radially extending flange 68. The piston therefore acts a check valve, subject to its engagement with the seal in the inflation assembly.

The precise configuration and shape of the piston is not important, nor is the position of the seal important. Rather, the selection of the spring tension/bias Sf and its ability to resist opening and promote piston closure at a given internal bladder pressure is important. The configuration therefore provides a relatively simple, cheap and self-regulating pressure system that maintains internal bladder pressures for as long as the external gas reservoir retains sufficient pressurized inflation gas (or other expandable fluid).

Preferably, the seal 88 operates to provide a soft cthsure such that gas continues to marginally over-inflate the bladder before shut-off the gas supply occurs. This soft closure can be achieved through selection of a compressive seal that establishes full integnty under a compressive load that must reach a predetermined safety factor.

The radially extending flange can actually be considered as a head, disc or floating diaphragm that moves into an out of engagement with the seaL whereas the stem is actually optional (although it facilitates assembly and positioning of the spnng 76). The spring can, in one embodiment, simply be fixed into a rear surface of a flat disc that operates as a moveable check valve.

To provide control over the point of opening of the valve (formed by the radially extending flange 68 and the seal 88), an adjustment screw 96 or the like may extend, for example, through a back of the regulator 60 and engage the spring. By turning adjustment screw 96. the amount of tension in the spring can be varied. i.e. increased or slackened, by reducing an effective overall length of the spring 76 between or by increasing the number of coils and the energy per unit length. In this respect, the adjustment screw can either engage the spring directly or can otherwise engage a base plate against which a base of the spring rests or is fixedly attached. The adjustment screw 96 is threaded through a seal that limits gas losses.

FIG. 4 is an alternative configuration for a moveable diaphragm (i.e. the radially extending flange 68) employed within the pressure regulator of FIG. 3. In contrast with FIG. 3, the outer surface 90 of the radially extending flange 68 includes a pierce/puncture pin 100 that is configured to puncture a seal or lid on a pressured gas reservoir. Again, to avoid loss of gas 99, the gas reservoir is preferably fixed to the inflation assembly such as by way of an internai thread, with the gas reservoir abutting against a suitably located gasket positioned within the inlet port 72. Other fixing methodologies will be understood.

Once the gas reservoir is exhausted or reduced, it is contemplated that a bulb pump connected via a tube may be used to replace any lost gas and thereby maintain or vary intemai pressure within one or more of the bladders (either collectively or individually).

The bulb pump thereby provides a degree of variance of internal pressure over that achieved by the spring in combination with the internal pressure. Alternatively, a connecting hose and mouthpiece may allow for exhaled air to be used to replace lost gas within the bladder. In both cases, the composite unit includes a secondary one-way valve that provides an ingress point for fluid (and specifically air) to be introduced into the Nadder(s) of the tourniquet cuff (or other inflatable device, as the case may be). The one-way valve is integrated into the fabric using any one of a number of known techniques, such as described herein and as readily understood by the skilled addressee.

The connecting hose then provides a communicating fluid path between the one-way valve and the bulb pump or mouthpiece.

It will be understood that unless features in the particular preferred embodiments are expressly identified as incompatible with one another or the surrounding context implies that they are mutually exclusive and not readily combinable in a complementary and/or supportive sense, the totality of this disclosure contemplates and envisions that specific features of those complementary embodiments can be selectively combined to provide one or more comprehensive, but slightly different, technical solutions.

It will, of course, be appreciated that the above descnption has been given by way of example only and that modifications in details may be made within the scope of the present invention. For example. whilst the preferred embodiment refers to an appfication in the context of tourniquets, the present invention has wider application to any self-inflating system that makes use of a gas reservoir, including (but not limited to lifesaving jackets, life rafts, belts and the 111cc). The attachment process of welding or otherwise fixing the automated pressure maintenance valve to the bladder to support rapid inflation of the bladder may be adapted as appropnate, as will be understood by the skilled addressee, to any of the envisioned application contexts, including life preservers and jackets. Also, while the preferred embodiment refers to the use of a steel spring, other forms of mechanically resilient assembly may be substituted therefore, including a piston and cylinder. The term "spring" should therefore be understood to be functional and to encompass a variety of equivalent assemblies readily understood by the skilled addressee.

Claims (10)

1. Claims I. An automated gas pressure regulator comprising: an inlet port configured. in use, to engage a pressurized gas bottle to receive pressurized gas therefrom; an outlet port in fluid communication with the outlet port; and a movable check valve disposed between the inlet port and the oudet port, the movable check valve having an inner surface and an outer surface; a gas seal engageable selectively by the outer surface of the check valve, the gas seal within the automated pressure regulator and configured such that, upon positive engagement by the check valve the inlet is isolated from the outlet port; and a spring abutting against the inner surface to positively bias the check valve against the seal automatically to regulate closure of the check valve and selectively to isolate the inlet port from the outlet port when a predetermined closure pressure is exerted on the inner surface of the check valve by a combination of the bias applied by the spring and a gas pressure acting on said internal surface.
2. 2. The automated gas pressure regulator of claim 1, further including means to vary the bias appfied by the spring.
3. 3. The automated gas pressure regulator of claim 1 or 2, wherein the check valve is a free-floating diaphragm.
4. 4. The automated gas pressure regulator of claim 1 or 2, wherein the check valve is a piston having a T-shaped section.
5. 5. The automated gas pressure regulator of any preceding claim, wherein the outer surface includes a pierce pin.
6. 6. A portable rapid inflation system comprising: an inflatable gas bladder; and an automated gas pressure regulator according to any preceding claim, the gas pressure regulator sealably coupled to the inflatable gas bladder; and a pressurized gas bottle coupled to the inlet port; wherein the automated gas pressure regulator is configured to control and substantially maintain inflation of the bladder at an inflation level having a predetermined internal pressure and wherein disengagement of the movable check valve relative to the seal occurs when a gas pressure (Pr) in the portable gas bottle is greater than a combination of an opposing internal gas pressure (Pt) within the gas bladder and the bias exerted by the spring.
7. 7. The portable rapid inflation system (40) according to claim 6, wherein the check valve is configured to open to allow re-inflation of the gas bladder at a point before a predetermined minimum internal pressure is reached.
8. 8. The portable rapid inflation system according to claim 6 or 7, wherein the system is selected from the group consisting of: a tourniquet; a life raft; and a life vest.
9. 9. An automated pressure regulator substantially as hereinbefore described with reference to FIGs. 3 and 4 of the accompanying drawings.
10. 10. A portable rapid inflation system substantially as hereinbefore described with reference to FIGs. 2 to 4 of the accompanying drawings.