Closure device

A closure device for a container of compressed gas, particularly a capsule having a water capacity in the range of 5 to 100 ml, comprises a shut-off valve 122 and a pressure-reducing valve 120, particularly a pressure regulating valve. The shut-off valve 122 is on the lower pressure side of the pressure-reducing valve 120. The closure device may also comprise a fill valve 118 to enable the container to be recharged with gas.

FIELD OF THE INVENTION

This invention relates to closure device for a container of compressed gas, particularly such a container which is of a sufficiently small size that it is able to be carried about the person or is able to be loaded in or fitted to a handheld device that delivers gas therefrom.

BACKGROUND OF THE INVENTION

It has been known for 100 years or more to store compressed gases in a gas cylinder. A conventional gas cylinder is relatively large and is not capable of being carried in comfort about the person or of being loaded into a handheld device. The gas cylinder typically stores gas at a pressure of up to 300 bar. The gas may be a permanent gas, in which case it remains in the gaseous phase, or a non-permanent gas which can be liquefied by the application of a sufficiently large pressure. The gas cylinder is closed by a shut-off valve. The valve is able to be opened manually to release the gas. Typically, although the gas is stored at a very high pressure, it is not required at such pressure. The user therefore typically fits a pressure regulator or other pressure-reducing valve to the cylinder in order to reduce the delivery pressure to a suitable value. The pressure reducing valve is therefore located downstream of the shut-off valve. Typical shut-off valves are configured so as to enable the cylinder to be filled. More recently, cylinder valves with integrated pressure regulators have been used. In all these cases the fill valve and the pressure regulator are downstream of the shut-off valve.

If the container of compressed gas is required to be fitted to a small, typically hand-held device, for example a soda-siphon or a cream whipper, a conventional thermal gas cylinder fitted with a cylinder valve is not used. Instead, the necessary gas is contained under pressure in a capsule having a water capacity of up to 100 ml. The capsule normally has a closure in the form of a pierceable seal. The capsule is engaged with a device including a hollow needle that pierces the seal in order to deliver gas. Such arrangements are generally used either when the gas concerned is a non-permanent gas stored primarily in the liquid state, or when it is desirable to release the gas as quickly as possible. In the former example, the rate of delivery of gas is limited by the rate at which the gas vaporises. The need for a downstream pressure reducing valve, for example a pressure regulator, is therefore typically reduced. In the latter example, the need to deliver the gas as quickly as possible for example, to inflatable devices such as air bags, means that a pressure-reducing valve should not be used.

There is, however, a need for a closure device for a small container of compressed gas which makes possible delivery of the gas at a reduced pressure and which avoids the use of pierceable or puncturable seals, such seals rendering the reuse of the containers sufficiently inconvenient for them normally to be thrown away.

SUMMARY OF THE INVENTION

According to the present invention there is provided a closure device for a container of compressed gas, the closure device comprising a shut-off valve and a pressure-reducing valve, characterised in that the shut-off valve is located on the lower pressure side of the pressure-reducing valve.

The invention also provides a container of compressed gas, typically a capsule or other container that is able to be held in the hand, the container being fitted with a closure device according to the invention.

The closure device and container according to the invention are suitable for the storage of either a permanent gas or a non-permanent gas.

The pressure-reducing valve is typically a pressure regulator.

The closure device comprises an external body housing the shut-off valve and the pressure-reducing valve, the external body being engagable with the container of compressed gas.

The external body comprises a first member engagable with the container of compressed gas and having a gas inlet and a second member including an outlet for the gas and housing the shut-off valve. The external body defines a passageway between the inlet and the outlet.

The terms “inlet” and “outlet” are used herein with reference to the closure device when it is being used to deliver gas to an appliance or the like.

The first member of the external body has a first internal chamber housing a fill valve including an internal body member, the first internal chamber communicating with the interior of the container when the closure device is an engagement therewith.

The first member of the external body typically has a fill port communicating with the first internal chamber.

The said inner body member typically cooperates with a spring-loaded O-ring sealing member to seal the fill port from the interior of the container when the closure is an engagement therewith, the O-ring sealing member being displaceable from its sealing position against the spring-loading by a gas pressure applied to the filling port.

Typically there is retaining nut for retaining the inner body member in position.

The inner body member defines part of the passageway between the said inlet and the said outlet.

The internal body member defines a seat for the pressure-reducing valve.

The first internal chamber typically communicates with a bursting disc housed in the first external body member.

There are a number of possible configurations for the pressure-reducing valve in order for it to act to regulate the downstream pressure. In one such arrangement, the pressure-reducing valve comprises an inner cap housed within the valve body, the inner cap bounding in part a second internal chamber within the valve body, the second internal chamber being in communication with the said inlet when the pressure-reducing valve is open; and a spring-loaded piston contained within the valve body, the piston comprising a piston head and a piston rod, the piston rod including a conduit forming part of the said passageway and providing communication between the second internal chamber and a gas space defined between the piston head and the shut-off valve, wherein the piston is operable to move between a closed configuration in which the piston rod prevents communication between the gas inlet and the second internal chamber and an open configuration in which the piston rod permits communication between the gas inlet and the second internal chamber.

In a preferred embodiment, the piston head is in a sealing engagement with the valve body via a piston head seal and the piston rod is in a sealing engagement with the inner cap via a piston rod seal contained within the second internal chamber, the piston rod seal being held in a fixed position within the chamber. Such an arrangement makes it possible to keep down the diameter of the piston rod and therefore facilitates the manufacture of the closure device to a size suitable for a container that it is capable of being held in the hand.

The first external body member typically comprises a collar, and the piston rod and seal is held between the collar and the inner gap. The main gas passageway typically extends through the collar. In such an arrangement, a first part of the main passageway terminates in an orifice adjacent to the second internal chamber, and the piston rod comprises a sealing pin at an end remote from the piston head, the piston rod being arrangement within the external body so that the sealing pin seals the orifice when the piston is in the closed position.

The tip of the sealing pin is conveniently chamfered to a point, and the piston rod is arranged within the external body so that the tip of the sealing pin enters into and seals the orifice when the piston is in the closed position. The chamfering of the tip of the sealing pin and the arrangement of the piston rod within the valve body are such that the sealing pin is typically caused to be centred within the orifice as the tip of the sealing pin enters the orifice when the piston moves from the open position to the closed position.

The orifice typically has a diameter of approximately 0.3 mm.

The pressure reducing valve typically further comprises a compression spring ranged within the external body to bias the piston towards the open position.

The compression spring typically encircles the inner cap and extends between a surface of the inner cap and a surface of the piston head.

A recess may be provided in the piston head and the compression spring may extend between the surface of the inner cap into the recess.

Typically the inner cap is in a sealing engagement with the first external body member via an inner cap seal, whereby build up of pressure within the second internal chamber, in the event it occurs, is operable to cause the said sealing arrangement to break, enabling the gas within the second internal chamber to be vented via a relief aperture provided in the second external body member.

The shut-off valve typically comprises a spring-loaded head which when the shut-off valve is in a closed position makes a sealing engagement with a valve seat via a shut-off valve seal, but which is displaceable against the bias of the spring to open the shut-off valve.

The spring of the shut-off valve is typically is a disc spring.

The inlet to the main passageway may receive a purge tube which extends into the container and terminates therein at a position remote from the closure device.

Typically, the closure device is in welded engagement with the container.

The drawings are not to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring toFIG. 1, there is shown a capsule102adapted to store compressed gas at elevated pressure. The chosen elevated pressure if the compressed gas is a permanent gas, for example, helium or oxygen or mixtures of helium and oxygen, maybe in the order of 190 bar, but may be higher or lower. Non-permanent gases, for example, carbon dioxide or nitrous oxide, are typically stored at lower pressures in the range of 50-100 bar. The capsule102is typically of a size and shape such that it may readily held in an adult human hand. It typically has a water capacity in the range of 5-100 ml, but larger sizes are possible.

As shown inFIG. 1, the capsule102is typically generally cylindrical in shape. It is formed with a mouth104. The capsule102is provided with a closure device106. The closure device106has an external body108welded or otherwise secured (for example, by screw threads) fluid-tight to the external surface of the capsule102defining the mouth104. The external body108of the closure device106typically has a diameter no greater than 20 mm at its widest point.

The body108has a passageway110extending axially therethrough between an inlet112communicating with the interior of the capsule102and an outlet114which typically has a configuration that enables the combination of the capsule102and the closure device106to be connected to a user device. In one example, the user device may be a hand-held generator of a non-thermal gaseous plasma. In another example, the user device may be a pair of nasal cannulae for administering oxygen or a life sustaining mixture of helium and oxygen to a person experiencing breathing difficulties. If desired, the user device (not shown) may be configured such that when mated with the outlet114of the closure device106it is effective to open the closure device106and thereby cause delivery of gas to the user device.

The inlet112to the passageway110may receive a purge tube116which extends into the interior of the gas capsule and terminates therein at a region remote from the mouth104, typically a region close to the bottom of the interior of the capsule102.

The external body108of the closure device106houses three different valves, namely a fill valve118, a pressure-regulating (or pressure-reducing) valve120, and a shut-off valve122. The pressure-regulating valve120is located upstream of the shut-off valve122. In other words, the shut-off valve122is on the lower pressure side of the pressure-regulating valve120. On the other hand, the fill valve118is on the higher pressure side of the pressure regulating valve120.

When the fill valve118is closed it shuts off communication between the interior of the capsule102and a fill port124formed at the external surface of the body108. When the fill valve118is open, however, communication between the fill port124and the interior of the capsule102is essentially unimpeded. In both the open position and the closed position of the fill valve118there is communication between the interior of the capsule102and the upstream or high pressure side of the pressure-regulating valve120.

The pressure-regulating valve120has a configuration which distributes forces acting on a valve member (not shown inFIG. 1) of the pressure-reducing valve120in a valve-opening direction and are those acting in a valve-closing direction such that the effect of the absolute value of the gas pressure in the capsule102is relatively small and therefore changes in that pressure have only a relatively small, if any, effect on the downstream gas pressure delivered by the combination of the capsule102and closure device106. In this way, the pressure-reducing valve, acts to regulate the downstream pressure.

The configuration of the pressure regulator120may be such as to deliver a chosen pressure in the range of 1 bar to 3 bar absolute substantially independently of the pressure in the capsule102.

The shut-off valve122typically has a valve member (not shown inFIG. 1) which is biased into a valve-closing position by the pressure of a spring (also not shown inFIG. 1). When the shut-off valve122is in the closed position, the pressure-regulating valve120closes of its own accord.

As previously described, connection of the closure device106to a user device (not shown) causes a force to be applied to the shut-off valve122to hold it open against the bias of the aforementioned spring. Gas will then be delivered from the capsule. Gas will then be delivered from the capsule102to the user device.

When the gas capsule102is exhausted, it may be refilled through the fill port124. If desired, a nozzle126(or other connector) may be fitted in the fill port124to enable the capsule102to be connected to a source (not shown inFIG. 1) of refill gas under a suitable pressure. Refill gas thus flows into the capsule102in order to re-charge it. The arrangement is typically such that the refill gas enters via refill passages (not shown inFIG. 1) formed in the closure device104. If the refill gas is of a different composition from the gas with which the capsule102was previously charged, the shut-off valve122may be held in an open position. As a result, the refill gas displaces residual gas from the capsule102through the purge tube116and out of the fill valve118. When a volume of gas approximately equal to the water capacity of the capsule102has been displaced therefore by the refill gas, the shut-off valve122may be allowed to close, thus ending purging. Continued flow of the refill gas into the capsule102causes it to be charged with the refill gas. When a chosen pressure has been reached, the source of refill gas may be removed and the refill valve118allowed to close.

The closure device106is typically fitted with a bursting disc128which bursts to relieve the pressure in the capsule102should an excess of pressure be generated therein. The bursting disc128is thus able to communicate with the interior of the capsule102at all times, irrespective of the positioning of any of the valves118,120and122.

Referring now toFIGS. 2 and 3, there is shown one particular embodiment of the kind of arrangement illustrated inFIG. 1. There is thus shown inFIG. 2a capsule202for the storage of a permanent or non-permanent gas essentially similar to the capsule102shown inFIG. 1. The capsule202has a mouth204. A closure device206engages in a fluid-tight manner the external surface of the mouth204of the capsule202. There may be a screw-threaded or welded seal therebetween. The welded seal may be made by TIG welding. When full, the pressure in the gas capsule may be in the order of 190 bar if the gas to be stored therein is a permanent gas. Higher or lower storage pressures may, however, be used.

The closure device206comprises an external body208. The external body208comprises a first body member210that effects the engagement between the mouth204of the capsule202and the closure device206. The first body member210engages a second body member212. The first body member210has a first internal chamber214housing a fill valve216which includes an inner body member218. The first internal chamber214communicates with the interior of the capsule202. The first external body member210has a fill port220communicating with the first internal chamber214. As shown inFIG. 2, the fill port220is fitted with a nozzle222which is able to be connected to a source (not shown) of pressurised refill gas.

The inner body member218is retained in position by a retaining nut224which engages the first body member210. The inner body member218is formed with a recess which locates an O-ring sealing member226that seals against a displaceable annular backing member228. The backing member228is urged by a compression spring230into a position in which the O-ring sealing member226prevents communication between the first internal chamber214, and hence the interior of the capsule202, and the fill port220if no refill gas pressure is applied to the fill port220. On the other hand, if a source of refill gas is connected to the nozzle222and a sufficient gas pressure is brought to bear on the remote side of the O-ring sealing member226relative to the backing member228, the pressure causes the O-ring to be displaced towards the gas capsule to a location at which it no longer makes sealing engagement with the inner body member218. Refill gas is thus able then to flow into the first internal chamber214. In the arrangement shown inFIG. 2, the internal chamber214communicates with the interior of the gas capsule via passages231formed in the retaining nut224. (In an alternative arrangement, not shown, the passages231can be omitted and the first internal chamber can communicate with the second part238of the axial passageway referred to hereinbelow.) Refill gas is thus able to enter the interior of the gas capsule202. Once the refill gas pressure is removed, the bias of the compression spring230urges the O-ring sealing member226back into a fill-valve sealing position.

The closure device206has an axial passageway232that extends between an inlet234provided through the centre of the retaining nut224to an outlet236provided in the second external body member212. A first part of the passageway232extends through the retaining nut224. The first part of the axial passageway232is in register with a second part238formed axially through the inner body member218. The second part238of the axial passageway232terminates at its end more remote from the capsule202in a narrow orifice240. The orifice240is formed in a face242of the inner body member218and has a circular rim which forms the seat of a pressure regulating valve244which typically takes the form of a needle valve. The seating arrangement for the needle (or pin) depends on its configuration. The pressure regulating valve244determines the pressure of which gas issues from the closure device206. When the pressure regulating valve244is open, gas passes from the orifice240into a bore (or second chamber)246of the first body member210, the bore246forming a third part of the passageway232. The bore246communicates with a shut-off valve248in an outlet region of the closure device206. The orifice240is provided in the centre of the face242of the inner body member218. The orifice240has a narrower bore that the rest of the second part238of the axial passageway232. The orifice240typically has a diameter of 0.2-0.3 mm. This size is close to the limit of size of hole that can be commercially drilled or moulded, without special arrangements and excessive cost. The second part238of the axial passageway232can be made by drilling from the end of the inner body member218remote from the orifice240. This arrangement simplifies manufacturing as it enables an orifice240with a narrow bore to be provided in the inner body member218. In alternative embodiments, the inner body member218can be made entirely as a moulding so as to reduce cost, particularly at higher manufacturing volumes.

Referring again toFIGS. 2 and 3of the drawings, the pressure regulating valve244has an axially displaceable valve member in the form of a sealing pin (or needle)250. The pin is guided by the bore246of the first body member210, which bore246forms part of the axial passageway232. The pin250has a chamfered tip254which is adapted to make a sealing engagement with the mouth of the orifice240. In order to facilitate such engagement the inner body member218is preferably formed of a plastics material such as nylon 66 or PEEK. In order to prevent any seepage of air into the gas passing through the pressure regulating valve244, a further O-ring sealing member256is engaged between a top region (as shown) of the inner body member218and a wall of the cavity within the first external body member210in which the inner body member218is received.

The pin250is formed integral with or is connected to a hollow piston rod258. The rod258is formed with a plurality of apertures260(of which one is shown inFIG. 2) such that in operation gas issuing from the orifice240is able to pass via the bore246through the apertures260into the interior of the hollow piston rod258. The interior of the piston rod258thus forms a continuation of the axial passageway232and leads the gas to the shut-off valve248.

The pressure-regulating valve244comprises an inner cap262housed within the second body member212, the inner cap262being positioned over a collar274which is integral with the first body member210and defines part of the bore246. A further gas space270is provided adjacent the shut-off valve248and is bounded in part by the second body member212and also in part by a piston head266connected to the piston rod258. In operation, when the pressure regulating valve244is open gas passes from the orifice240into the gas space246, through the apertures260and into the interior of the hollow piston rod258and from there into the gas space270. The piston head266is operable to move in a third internal chamber264bounded by the second body member212between a position in which the pressure regulating valve244is open and a position in which the pin250closes the orifice240and hence the pressure regulating valve244.

The piston head266is in a sealing engagement with the second body member212of the external valve body208via a piston head seal268in the form of an O-ring and the piston rod258is in a sealing engagement with the inner cap via a piston rod seal272also in the form of another O-ring located around the piston rod258within the inner cap262. Typically, the sealing ring272is bonded to the inner cap262. Even if not so bonded, displacement of the piston rod seal272would in any event be prevented the collar274.

The pressure regulating valve244further comprises a compression spring276arranged within the external body208to bias the piston head266towards a position in which the pressure regulating valve244is open, the pin250failing to make a sealing engagement with the orifice240. The compression spring276encircles the inner cap262and extends between the external surface of the inner cap262and a surface of the piston head266. Typically a recess278is provided in the piston head266and the compression spring276extends between a surface of the inner cap262into the recess278.

In operation, the pressure regulating valve244typically reduces the pressure of the gas from a storage pressure to a delivery pressure typically in the order of 1 to 3 bar. In order to facilitate this pressure reduction, the orifice240is typically of a narrow diameter, say in the range of 0.2-0.3 mm. The delivery pressure of gas remains relatively unaltered notwithstanding the fact that, in use, the pressure in the gas capsule202falls from a maximum value when full (say 190 bar) to a minimum value of approaching 1 bar when nearly empty. The arrangement of the pressure regulating valve244is such that in normal gas delivery operation a static equilibrium is achieved between forces acting in a valve-opening direction and forces acting in a valve-closing direction with the result that the pin250is maintained in a position in which the pressure regulating valve244is open. This position is illustrated inFIG. 3of the drawings. The relationship between the pressure in the gas space270and the pressure in the gas space in the bore246when the pressure regulating valve244is in static equilibrium is as follows:
A1P1+(A2−A1)P2FS−P2A3=0  Equation 1
where A1is the cross-sectional area of the orifice240, A2is the cross-sectional area of the piston rod258contained within the piston rod O-ring272. A3is the cross-sectional area of the piston head266, F$is the force exerted by the compression spring276, and P1and P2are the pressures at which the gas leaves the orifice240and enters the gas space270, respectively.

From the above, it follows that the extent to which the pressure P2varies at equilibrium as the pressure P1varies is highly dependent upon the cross-sectional area A1of the orifice240. Equation 1 can be rearranged as follows:
P2=(A1P1+FS)/A3−A2+A1)  Equation 2

It can be deduced from Equation 2 that it is desirable to make the value of A1P1relatively small in comparison with the value of FS so as to achieve a pressure regulating effect. The table below illustrates the diameter of the piston head266required to maintain the outlet or delivery pressure within plus or minus 5% of 3 bar as the pressure in the gas capsule falls from a maximum of 200 bar to a minimum of 10 bar.

It is to be understood from the Table that it is desirable to minimise the diameter of the piston head266in order to achieve good pressure regulation. It is therefore desirable to minimise the diameter of the orifice240. We recommend an orifice diameter in the order of 0.3 mm because such a diameter can be achieved by standard manufacturing methods.

It is also follows from the static equilibrium equation that it is desirable to minimise the effective cross-sectional area A2of the piston rod258as this value also has an effect on the required size and dimensions of the piston head266and therefore the overall dimensions of the valve244itself. The effective diameter of the piston rod266is minimised by fixing the position of the piston rod O-ring seal272within the inner cap262such that it does not move with the piston rod258.

If the size of the orifice is no greater than 0.3 mm it is possible to keep the diameter of the valve244to below 20 mm.

If the shut-off valve248closes, for example, by removal of a member connecting the closure device206to a user device (not shown), the pressure in the bore246equalises with the pressure in the gas space270bounded in part by the piston head266. As a result, the net force acting in a valve-closing direction becomes sufficient to overcome the bias of the compression spring276and the pressure regulating valve244closes. To assist with aligning the pin250with the orifice240, when the pressure regulating valve244closes, the tip254of the pin250is chamfered to a point. As the pin250enters the orifice240, the chamfered portion may bear against the surface at the mouth of the orifice240and this will have a centring action on the pin250. It is therefore not normally possible for the tip254of the pin250to come into contact and cause any damage to the wall of the inner body member218defining the orifice240.

The internal surface of the second body member212is, provided with a shoulder280. The shoulder280limits the upward (as shown) travel of the piston head266. The shoulder280ensures that when the shut-off valve248is open with a valve-member282(described below) extending into the gas space270, there can be no contact between the valve member282and the piston head266.

The closure device206has the following features to ensure that any excess pressure is safely vented to atmosphere. Should there, for example, be a build-up of gas pressure in the bore246, the inner cap262is lifted away from the first body member210against the bias of the compression spring276and gas is allowed to escape past an O-ring sealing member284and flow out of the second body member212via the third internal chamber264and vent passages286provided in the second body member212. In normal operation of the closure device206, the O-ring seal284prevents such flow and venting of gas and this event occurs through, say, the apertures260in the piston rod258becoming blocked. On the other hand, should an excess pressure be created in the first internal chamber214(if, for example, the gas capsule itself is filled to too great a pressure) the first body member210is provided with a bursting disc288in communication with the first internal chamber214. The bursting disc288is typically provided with an external cap290protecting the bursting disc288from external damage.

The previously mentioned shut-off valve248is provided at an upper region (as shown) of the closure device206. The shut-off valve248typically comprises the previously-mentioned valve member (or head)282which when the shut-off valve248is in a closed position makes a sealing engagement with a valve seat292, typically formed integrally with the second body member212, via a shut-off O-ring valve seal294. The valve member or head282is displaceable against the bias of a disc spring296to open the shut-off valve. In one typical arrangement, the valve member or head282is provided with an axial rod299which may be formed integral with the valve head282. Engagement of a user device (not shown) with a port298at the outlet236of the closure device206can be arranged to cause an actuator (not shown) to bear against a rod299and force the valve member282out of engagement with valve seat292so as to permit gas to flow out of the closure device from the gas space270. A gas pressure differential is thus created between the pressure in the gas space270and the pressure in the gas space sufficient for the pressure regulating valve244to open with the result that gas is able to be delivered from the capsule202. Withdrawal of the actuator causes the bias of the disc spring296to close the shut-off valve248. This in turn causes the pressure-regulating valve244to close.

The overall dimensions of the closure device206can typically be kept to not greater than 50 mm in height and not greater than 20 mm in maximum diameter. The closure device206is thus, for example, able to be fitted to and to close a standard pressurised gas capsule202of, say, approximately 20 ml water capacity without rendering it difficult to hold the capsule in the hand or carry it about one's person. Because the closure device206is able to regulate the pressure which gas is delivered from the capsule, it becomes available for a range of personal uses which have hitherto required a conventional gas cylinder which cannot readily be carried about ones person.

The closure device206is shown inFIG. 2in its closed position and inFIG. 3in its open position. The piston head266typically travels from 1-2 mm between the closed position and a fully open position. The valve member282may have a configuration which facilitates passage of gas in the open position. As shown inFIG. 3, it may have a chamfered surface302for this purpose, whereas in the embodiment shown inFIGS. 4 and 5, the valve member282is of a frusto-conical configuration for the same reason.

The embodiment shown inFIGS. 4 and 5omits the nozzle222. When it is required to replenish or refill the capsule202, a probe310is inserted in the fill port220. The probe310is provided with an internal sealing member312which is adapted to engage and seal a filling nozzle (not shown) at the end of a filling line (not shown). The probe310is provided with an external groove314which is able to receive a circular clamping member (not shown) to prevent accidental disconnection of the filling line from the probe310.

In other respects, the embodiment of the closure device206shown inFIGS. 4 and 5is essentially the same in configuration and operation as the embodiment shown inFIG. 2or that shown inFIG. 3. InFIG. 4the closure device206is shown in its closed position, and inFIG. 5, in its open position.