GB2485529A

GB2485529A - Locking mechanism to hold a keg valve open

Info

Publication number: GB2485529A
Application number: GB1018997.5A
Authority: GB
Inventors: Jessica Rundin; Mikael Quasters
Original assignee: Petainer Lidkoeping AB
Current assignee: Petainer Lidkoeping AB
Priority date: 2010-11-10
Filing date: 2010-11-10
Publication date: 2012-05-23
Anticipated expiration: 2030-11-10
Also published as: GB2485529B; GB201018997D0; WO2012062874A1

Abstract

A closure 10 for a pressure vessel such as a cask, keg 12 or the like comprises a housing, at least one displaceable valve element movable between an open configuration and a closed configuration and a lock mechanism capable of holding the valve element in the open configuration, the lock mechanism having at least one locking element 88 movable transverse to the direction of movement of the valve element from an unlocked state to a locked state. Preferably, the locking element has a camming action and in use, the or each locking element follows a labyrinthine slot having five detent positions 108,110,112,114,116 allowing the valve to open and close and the keg is filled, transported and dispensed from, with the locking element or elements holding the valve open after the contents of the keg have been dispensed. Preferably the keg is made from a plastic material such as blow-moulded PET and the closure from injection-moulded plastics such as polyester, polyolefin, polyamide or the like. In use, the closure ensures that the keg cannot be left pressurised after use and that it cannot be refilled with the closure being reclosed afterwards.

Description

I

Keg closure with safety mechanism This invention relates to pressurised vessels such as kegs for storing, transporting and dispensing beverages. The invention relates particularly to a closure for a keg, the closure having a safety mechanism to prevent the closure being re-closed after use. This ensures that the keg cannot be left pressurised after use and also that it cannot be refilled with the closure being re-closed afterwards.

Kegs are widely used for the distribution and service of beverages such as beer. A closure in a neck of the keg typically includes a filling and dispensing valve that defines multiple flow paths through the closure. In this way, during filling when the keg is usually inverted, beverage can be injected into the keg through the closure via a first flow path while displaced gas can exit the keg through the closure via a second flow path. Conversely, during dispensing, a propellant gas (typically nitrogen or carbon dioxide) can be injected into the keg through the closure via the first flow path to force beverage out of the keg through the closure along the second flow path. In the most common well-type' arrangement, the closure comprises concentric valve elements and concentric flow paths.

When filling the keg at a filling station on a production line, the keg is usually inverted for use with beer and carbonated soft drinks although it could be upright for other beverages, especially those without effervescence, and a filling head is coupled to the closure to form a seal with the closure. The filling head has one or more formations that press against one or more spring-loaded valve elements of the closure to open the flow paths through the closure. Air inside the keg is flushed out with a relatively inert gas, for example carbon dioxide, and beverage is then injected into the keg via a liquid line connected to the filling head. Gas displaced from the keg by the incoming beverage is forced out through a vent in the filling head. When the keg is removed from the filling station, the filling head is uncoupled from the closure and the valve elements of the closure therefore snap shut under spring loading, sealing the beverage and any remaining inert gas within the keg.

For the purpose of dispensing the beverage, a dispense head is coupled to the closure to form a seal with the closure. The dispense head has a lever that, when depressed, extends one or more plungers corresponding to the formations of the filling head. The plunger(s) therefore press against one or more valve elements of the closure to re-open the flow paths through the closure. Those flow paths communicate with gas and liquid lines connected to the dispense head. A propellant gas is injected into the keg from an external source connected to the gas line. Beverage is then forced out of the keg when a tap in the liquid line is opened to dispense the beverage.

When the dispense head is coupled to the closure, the propellant gas is injected into the keg at super-atmospheric pressure. The keg will remain under super-atmospheric pressure unless and until that gas is vented. It is recommended for safety purposes to vent the propellant gas from the keg when the dispense head is uncoupled from the closure, most commonly when the keg has been emptied and is being interchanged with a fresh, full keg. For this purpose, some dispense heads have a purge valve that is operable to vent propellant gas from the keg before the dispense head is uncoupled from the closure.

However, not all dispense heads have a purge valve and even those that do have a purge valve may not be operated correctly. In practice, a user will often be in a hurry to swap empty kegs for full kegs while dispensing beverages in a busy bar and may not therefore take the time necessary to vent the propellant gas from the empty keg.

Instead, the user may simply remove the dispense head from the closure, allowing the spring-loaded valve elements of the closure to snap shut and hence to close the flow paths through the closure. The result is that the empty keg remains pressurised, which may not be apparent upon viewing the keg. This is a particular problem where a keg is of flexible material such as blow-moulded polyethylene terephthalate (PET), which is intended to allow the keg to be crushed after use for recycling rather than being returned intact for refilling like a rigid metal keg. Clearly a pressurised keg is not easily crushable. Also, in safety terms, it is undesirable for a pressurised keg to be punctured or ruptured, for example if an attempt is made to crush the keg during waste disposal while believing that the keg is not pressurised.

Another problem is that if the valve element(s) of the closure can still be opened and closed after the original beverage has been dispensed, the keg could possibly be re-filled in an unauthorised manner. For example, the keg could be re-filled with a beverage that is not of the appropriate quality; certainly, the keg is unlikely to be re-filled under the controlled conditions necessary to deliver a beverage in optimum condition. This is particularly undesirable as the keg may bear the brand of the original beverage supplier, whose reputation may be damaged by apparently supplying an inferior product. The keg could even be re-filled with a liquid that is not intended for human consumption and that could be dangerous to drink. Unauthorised refilling may not be apparent from a cursory inspection of the keg.

For these reasons, various keg closures have been proposed in which a valve element can close after filling but cannot close again after dispensing. For example, the proposal disclosed in US 4909289 to Hagan et al employs a ratchet arrangement that limits the number of valve openings to allow keg testing and keg filling procedures before the valve element locks open after dispensing.

The proposal in US 4909289 is impractical for various reasons. For example, the number of parts in its mechanism, and the way in which those parts interact, leads to long tolerance chains. This renders the mechanism vulnerable to failure where the combined tolerance of the parts causes excessive dimensional fluctuations between different assemblies. Also, the mechanism is not capable of handling the wide variety of filling heads and dispense heads that are available on the market.

A later proposal disclosed in DE 10 2007 036 469 to Schafer Werke involves depressing a valve element to a lesser extent upon coupling a filling head to the closure for filling (i.e. the filling stroke) and to a greater extent upon coupling a dispense head to the closure for dispensing (i.e. the dispense stroke). The greater movement of the valve element through the dispense stroke causes the valve element to lock in a depressed position such that when the dispense head is removed after dispensing, the valve element cannot move back to the closed position.

The proposal disclosed in DE 10 2007 036 469 requires the filling stroke to be shorter than the dispense stroke. However, the use of a well-type fitting involves a filling stroke that is often equal to or sometimes longer than the dispense stroke. The proposal in DE 10 2007 036 469 cannot handle situations where the filling stroke is longer than or equal to the dispense stroke because the valve element will either lock open prematurely during the filling procedure or will fail to lock open after the dispensing procedure.

It is against this background that the present invention has been devised. The invention resides in a closure for a pressure vessel such as a keg, the closure comprising: a housing; at least one valve element that is movable along an axis with respect to the housing into closed and open states; and a lock mechanism that is capable of holding the valve element in the open state; wherein the lock mechanism comprises a locking element that is coupled to the valve element to move in a direction transverse to said axis in response to said movement of the valve element, the locking element being movable between an unlocked position in which the valve element can attain the closed state and a locked position in which the valve element is held in the open state.

The closure of the invention is conventionally operable by axially inward movement of the valve element with respect to the housing between the closed and open states.

The lock mechanism employed by the closure of the invention does not suffer from the long tolerance chains of US 4909289 or the inability of US 4909289 to handle the variety of filling heads and dispense heads that are on the market. Also, unlike DE 10 2007 036 469, the mechanism of the invention can be used even if the filling stroke is equal to or longer than the dispense stroke.

In the preferred embodiment of the invention to be described below, the closure includes a second valve element concentric with and movable axially relative to a first valve element.

Conveniently, a cam mechanism acts between the valve element and the locking element to convert axial movement of the valve member into transverse movement of the locking element. The cam mechanism may comprise a cam path associated with one of the valve element and the locking element and a drive element associated with the other of the valve element and the locking element. Then, relative movement between the drive element and the cam path converts axial movement of the valve member into transverse movement of the locking element.

In the embodiment to be described, the drive element is associated with the valve element and the cam path is associated with the locking element. In that case, the drive element moves generally parallel to the axis of movement of the valve element to drive transverse movement of the locking element by virtue of relative movement between the drive element and the path. However it would be possible to reverse the arrangement so that cam path is associated with the valve element and the drive element is a cam follower that drives transverse movement of the locking element in response to axial movement of the cam path.

The cam path suitably comprises a succession of detent positions for the drive element, with successive detent positions being spaced parallel to the axis of movement of the valve element. To impart transverse movement to the locking element, it is preferred that successive detent positions of the cam path are spaced in a direction transverse to the axis of movement of the valve element.

Where the closure of the invention is arranged for reciprocation of the valve element along its axis of movement, successive detent positions of the cam path suitably alternate between axially inward and axially outward positions with respect to the pressure vessel. In that case, it is preferred that the locked position corresponds to an axially outward detent position that extends axially outwardly to a lesser extent than a previous axially outward detent position of the cam path. This is one way in which axially outward movement of the valve element may be restricted in the final reciprocal movement into the locked position, to hold the valve element in the open state after dispensing.

In the embodiment to be described, the cam path comprises, in succession: a first detent position in which the valve element may adopt the closed state; a second detent position in which the valve element may adopt the open state; a third detent position in which the valve element may adopt the closed state; a fourth detent position in which the valve element may adopt the open state; and a fifth detent position in which the locking element is in the locked position and the valve element is held in the open state.

Elegantly, transverse movement of the locking element may be achieved by the locking element turning about the axis of movement of the valve element, between the unlocked position and the locked position. For example, the locking element may be a collar that encircles the valve element.

Upon transverse movement of the locking element into the locked position, locking may be achieved by a pawl associated with the valve element being aligned with a lock formation of the locking element. For example, the lock formation may be disposed axially outwardly of the pawl when the locking element is in the locked position. This is another way in which axially outward movement of the valve element may be restricted by movement of the locking element into the locked position, to hold the valve element in the open state after dispensing. Conversely, when the locking element is in the unlocked position, the lock formation of the locking element may be displaced transversely with respect to the pawl, whereby the pawl may bypass the lock formation to allow the valve element to assume the closed state.

Of course, the inventive concept extends to a pressure vessel such as a keg, fitted with the closure of the invention.

In order that the invention may be more readily understood, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 a is a cut-away side view of a closure in accordance with the invention, showing the closure before filling with both valve elements closed; Figure 1 b is an enlarged sectional side view of the closure in the state shown in Figure Ia; Figure 2 is a perspective view of a seal ring that is part of the closure shown in Figures Ia and Ib; Figure 3 is a perspective view of a spear component that is part of the closure shown in Figures Ia and Ib; Figure 4 is a perspective view of a locking collar that is part of the closure shown in Figures Ia and Ib; Figure 5 is a cut-away side view of the closure that corresponds to Figure I a but shows the closure during filling when a filling head has been coupled to the closure, with both valve elements open; Figure 6 is a cut-away side view of the closure that corresponds to Figures I a and 5 but shows the closure after filling when the filling head has been uncoupled from the closure, with both valve elements again closed; Figure 7 is a cut-away side view of the closure that corresponds to Figures Ia, 5 and 6 but shows the closure during dispensing as when a dispense head has been coupled to the closure, with both valve elements again open; Figure 8a is a cut-away side view of the closure that corresponds to Figures Ia, 5, 6 and 7 but shows the closure after dispensing as when the dispense head has been uncoupled from the closure, with one valve element now permanently open; and Figure 8b is an enlarged sectional side view of the closure in the state shown in Figure 8a.

Figures Ia and I b of the drawings show a well-type closure 10. The closure 10 is arranged to be fitted into the neck 12 of a keg, shown schematically in Figure 1 b. In this example, the keg is of plastics material such as blow-moulded PET. The components of the closure 10 are made predominantly of injection-moulded plastics materials such as polyester, polyolefin, polyamide or the like, except where stated otherwise below. It is emphasised that the materials used for the keg and the closure 10 and their methods of manufacture are merely preferred and are not essential to the broad inventive concept.

The closure 10 has a generally tubular housing 14 shaped to fit closely within the tubular neck 12 of the keg. The housing 14 is retained on the keg by a snap ring 16 that resiliently engages circumferential ridges 18 projecting laterally from the exterior of the neck 12. The housing 14 surrounds and supports concentric valve elements that are axially displaceable inwardly against spring bias toward the interior of the keg to open them. As the valve elements open, they open respective concentric flow paths extending through the closure 10 and into the keg.

As Figure 1 b shows, an outer valve comprises a first valve element including an annular seal ring 20. The seal ring 20 comprises a rigid core 22 sandwiched between resilient upper and lower seal components 24 and 26 respectively.

The seal ring 20 is supported by, and moves axially with, a tubular spear connector 28. The seal ring 20 and the spear connector 28 are shown in more detail in Figures 2 and 3 respectively and will be described more fully later with reference to those drawings.

An outer coil spring 30 of stainless steel surrounds the lower portion of the spear connector 28 and acts in compression between the housing 14 and the spear connector 28. The outer coil spring 30 biases the spear connector 28 outwardly away from the interior of the keg. This urges the seal ring 20 into sealing contact with an outer valve seat 32 that extends radially inwardly from the housing 14 with respect to the central longitudinal axis of the neck 12. To aid sealing, the resilient upper seal component 24 of the seal ring 20 has an integrally-moulded outer sealing rim 34 that seals against the outer valve seat 32. To aid location, the outer valve seat 32 has a frusto-conical inner surface 36 that cooperates with the seal ring 20 when the outer valve is closed.

The spear connector 28, in turn, surrounds and supports a second valve element being a plug 38 that is movable axially with respect to the spear connector 28 relative to the seal ring 20. The plug 38 comprises a head 40 and a stem 42 in a generally T-shape arrangement. The head 40 of the plug 38 cooperates with the resilient lower seal component 26 of the seal ring 20 to define an inner valve. The lower seal component 26 is generally flat but comprises concentric integrally-moulded sealing rims 44, 46. An outer sealing rim 44 seals against the top of the spear connector 28, and an inner sealing rim 46 seals against a shoulder 48 projecting radially from the head 40 of the plug 38.

An inner coil spring 50 of stainless steel surrounds the stem 42 of the plug 38 and acts in compression between the head 40 of the plug 38 and the spear connector 28.

The inner coil spring 50 thus urges the head 40 of the plug 38 outwardly away from the interior of the keg, into sealing contact with the lower seal component 26 of the seal ring 20.

Referring now to Figure 2, the seal ring 20 comprises a cylindrical inner wall 52. The inner wall 52 terminates at its upper end in an inner ring 54 of the upper seal component 24. The inner ring 54 lies in a plane orthogonal to the inner wall 52. An outer wall 56 depending from the inner ring 54 has a frusto-conical lower section 58 that complements the frusto-conical surface 36 of the outer valve seat 32 of the housing 14. The outer sealing rim 34 is disposed outwardly of the lower section 58 of the outer wall 56.

The rigid core 22 of the seal ring 20 extends radially outwardly below the upper seal component 24. The core 22 has various formations depending from its edge in diametrically-opposed pairs, including snap-fit prongs 60 and lugs 62 that, respectively, engage the seal ring 20 with the spear connector 28 and prevent the seal ring 20 turning with respect to the spear connector 28. L-shaped pawls 64 also depend downwardly and outwardly from the edge of the core 22; the pawls 64 are capable of locking axial movement of the spear connector 28 after dispensing, as will be explained later. Only one set of prongs 60 and one of the pawls 64 are visible in Figure 2; the opposed set of prongs 60 and the opposed pawls 64 are hidden on the far side of the seal ring 20 in that view.

Figure 3 shows the spear connector 28 in isolation. At its upper or outer end, the spear connector 28 has a radially-extending flange 66 with diametrically-opposed pairs of formations 68, 70, 72 spaced around its circumference. Those formations 68, 70, 72 are in alignment with, and complementary to, the formations that depend from the outer edge of the seal ring 20, namely the prongs 60, lugs 62 and pawls 64 respectively. More specifically, the flange 66 has: snap-fit formations 68 that receive and engage the prongs 60; fingers 70 that embrace and engage with the lugs 62; and notches 72, each of which accommodates the downward leg of a respective pawl 64.

Thus, when the seal ring 20 is aligned with the spear connector 28 to bring the prongs 60, lugs 62 and pawls 64 into mutual alignment with their complementary snap-fit formations 68, fingers 70 and notches 72, the prongs 60 engage with the snap-fit formations 68 and the lugs 62 fit between the fingers 70. As noted above, this engages the seal ring 20 with the spear connector 28 and prevents the seal ring 20 turning with respect to the spear connector 28.

At its lower or inner end, the spear connector 28 has a push-fit male fitting 74 for a flexible tube (not shown) that communicates with the hollow interior of the spear connector 28. The tube is typically of extruded plastics material such as polyethylene and extends into the base of the keg from the fitting 74.

At an intermediate level between its ends, the spear connector 28 has four integrally-moulded tabs 76 that project radially outwardly from the tubular wall 78 of the spear connector 28. The tabs 76 lie in planes that are equi-angularly spaced about, and intersect along, the central longitudinal axis of the spear connector 28. Each tab 76 is supported by integrally-moulded webs 80, and has an outer edge 82 that is parallel to the central longitudinal axis of the spear connector 28. The outer edges 82 of the tabs 76 define bearing surfaces that support and centre the spear connector 28 for axial sliding movement within the cylindrical inner wall 84 of the tubular housing 14, as can be seen in Figure 1 b. At their axially inner ends, the tabs 76 are joined by an integrally-moulded frusto-conical flange 86 that surrounds the tubular wall 78 of the spear connector 28. The outer coil spring 30 acts against the underside of the flange 86.

A diametrically-opposed pair of pins 88 are disposed between the flange 66 at the outer end of the spear connector 28 and the tabs 76. Only one of the pins 88 is visible in Figure 3 as the other pin 88 is hidden on the far side of spear connector 28.

The pins 88 are approximately angularly aligned with the notches 72 that accommodate the pawls 64. The pins 88 project radially outwardly from the tubular wall 78 of the spear connector 28 and are supported by webs 90. The pins 88 interact with a rotary locking collar 92 to drive angular movement of the collar 92 around the central longitudinal axis of the spear connector 28. That collar 92 is shown in isolation in Figure 4 of the drawings and will now be described in detail.

The collar 92 shown in Figure 4 of the drawings comprises a tubular wall 94 that lies generally parallel to the central longitudinal axis of the spear connector 28 and is a sliding fit within the cylindrical inner wall 84 of the tubular housing 14. The wall 94 is penetrated by pairs of parallel slots 96 in four equ i-angularly spaced locations to define integially-moulded legs 98 that are cantilevered to the wall 90 at their upper ends and that each have an outwardly-extending foot 100 at their lower free end. The legs 98 can deflect resiliently inwardly to allow the feet 100 to clear the cylindrical inner wall 84 when the collar 92 is inserted into the tubular housing 14.

As Figure 1 a shows, the housing 14 has four equ i-angularly spaced slots 102, each of which extends circumferentially to an extent greater than the width of each foot 100. When the feet 100 reach respective slots 102 in the housing 14-as shown in Figure Ia -upon insertion of the collar 92 into the bottom of the housing 14, the legs 98 urge the feet 100 resiliently outwardly to engage the slots 102 as a snap-fit. As the slots 102 are wider circumferentially than the feet 100, the feet 100 afford the collar 92 limited angular movement about the central longitudinal axis of the spear connector 28 but they restrain movement of the collar 92 axially, parallel to that axis.

Axial location of the collar 92 is completed by an inwardly-facing shoulder 104 of the housing 14.

The tubular wall 94 of the collar 92 further comprises diametrically-opposed cam gates 106 that receive the pins 88. The cam gates 106 serve as cam followers that index the collar 92 in angular increments in response to reciprocal axial movement of the pins 88 due to corresponding movement of the spear connector 28. Each cam gate 106 comprises a convoluted labyrinth slot that is shaped to define five detent positions 108, 110, 112, 114 and 116 through which the pins 88 move in four successive reciprocal movements, as will be explained.

The collar 92 further comprises an inwardly-facing flange 118 along the top edge of the tubular wall 94. That flange 118 is discontinuous, being entirely cut away in alignment with a start position 106 of each cam gate 106 to allow the pins 88 to bypass the flange 118 upon assembly of the closure 10. Elsewhere around the circumference of the collar 92, the width of the flange 118 varies between narrower portions 120 and wider portions 122. The narrower portions 120 of the flange 118 allow clearance for the pawls 64 of the seal ring 20. Conversely, the wider portions 122 of the flange 118 are arranged to engage the pawls 64 of the seal ring 20 when sufficient stepwise angular movement of the collar 92 takes place in response to reciprocal axial movement of the pins 88. That engagement between the pawls 64 and the flange 118 prevents the seal ring 20 returning to its closed position against the outer valve seat 32 after dispensing. This will be explained in more detail later, with specific reference to Figures 8a and 8b of the drawings.

More generally, reference will now be made to Figures Ia, Ib, 5, 6, 7, 8a and 8b of the drawings to describe the sequence of operation of the closure 10 in detail. A filling head and a dispense head for use with the closure 10 of the invention are conventional and so are omitted from those drawings.

Figures la, lb and 6 of the drawings show the closure 10 with both valve elements closed before and after filling: thus the outer sealing rim 34 of the upper seal component 24 is in sealing contact with the outer valve seat 32 and the head 40 of the plug 38 is in sealing contact with the inner sealing rim 46 of the lower seal component 26.

Figures Sand 7 of the drawings show the closure 10 with both valve elements open, as during filling and dispensing respectively. When a filling head is coupled to the closure 10, concentric formations on the filling head press inwardly on the seal ring and on the plug 38, depressing them toward the interior of the keg. Similarly when a dispense head is coupled to the closure 10, concentric plungers on the dispense head also press inwardly on the seal ring 20 and on the plug 38, depressing them toward the interior of the keg.

When the seal ring 20 is pushed inwardly toward the interior of the keg, the outer sealing rim 34 moves away from the outer valve seat 32 to permit fluid flow along an outer flow path around the spear connector 28. Similarly when the plug 38 is also pushed inwardly toward the interior of the keg with respect to the seal ring 20, the plug 38 moves away from the inner sealing rim 46 to permit fluid flow along an inner flow path around the stem 42 of the plug 38.

In practice, beverage will flow into the keg along the outer flow path during filling in Figure 5 and from the keg along the inner flow path during dispensing in Figure 7.

Conversely, gas will flow from the keg along the inner flow path during filling in Figure and into the keg along the outer flow path during dispensing in Figure 7. The beverage and gas flows specified during filling assume that the keg is inverted during filling, which is conventional for effervescent drinks such as beer. However it is also possible to fill the keg with suitable beverages when upright, in which case beverage will flow into the keg along the inner flow path and gas will flow from the keg along the outer flow path.

In general terms, the above features of the closure 10 are largely conventional. The invention resides in the lock mechanism that, in this example, comprises the collar 92 and the seal ring 20 attached to the spear connector 28.

Initially, before filling, the spear connector 28 is urged by spring bias to press the attached seal ring 20 against the outer valve seat 32. Similarly the plug 38 is urged by spring bias against the seal ring 20. This situation is shown in Figures Ia and I b, in which the outer and inner valves are therefore closed. Each pin 88 is in the start detent position 108 in its respective cam gate 106 of the collar 92.

When the seal ring 20 and the plug 38 are depressed by plungers of a filling head to open the outer and inner valves during filling as shown in Figure 5, the seal ring 20 moves the spear connector 28 axially inwardly toward the interior of the keg against spring bias. The seal ring 20 moves with the spear connector 28 and the pawls 64 of the seal ring 20 pass the flange 118 of the collar 92 by virtue of clearance at narrower portions 120 of the flange 118. Each pin 88 moves axially inwardly from the start detent position 108 in its respective cam gate 106 to a second detent position 110. The second detent position 110 is axially inward of, and angularly displaced about the collar 92 with respect to, the start detent position 108. Thus, as the pins 88 move axially inwards, the collar 92 indexes angularly about the central longitudinal axis of the closure 10.

When filling is complete and the outer and inner valves are allowed to close again as shown in Figure 6, the force of the outer coil spring 30 acting on the spear connector 28 moves the pins 88 axially outwardly. Each pin 88 moves axially from the second detent position 110 in its respective cam gate 106 to a third detent position 112. The third detent position 110 is axially outward of, and further angularly displaced about the collar 92 with respect to, the second detent position 110. Thus, as the pins 88 move axially outwards, the collar 92 undergoes further angular stepwise movement about the central longitudinal axis of the closure 10.

Once the keg is filled, the closure 10 is preferably covered with means for dust protection and tamper evidence, such as a foil cap (not shown). The filled keg may then be stored and delivered to customers for dispensing as required. To facilitate transportation, a handle (not shown) may be attached to the neck 12 of the keg.

Figure 7 shows that when the seal ring 20 and the plug 38 are depressed again to open the outer and inner valves for dispensing, the seal ring 20 moves the spear connector 28 axially inwardly against spring bias toward the interior of the keg.

Consequently, the pins 88 move again axially inwardly from the third detent position 112 to a fourth detent position 114 in their respective cam gates 106. The fourth detent position 114 is axially inward of, and further angularly displaced about the collar 92 with respect to, the third detent position 112. Thus, as the pins 88 move axially inwards, the collar 92 undergoes still further angular movement about the central longitudinal axis of the closure 10.

When the seal ring 20 and the plug 38 are released again as shown in Figures 8a and 8b, the pins 88 move for a final time axially outwardly from the fourth detent position 114 to a fifth detent position 116 in their respective cam gates 106. The fifth detent position 116 is axially outward of, but angularly aligned with, the fourth detent position 114. Now, the inner valve is able to close because the head 40 of the plug 38 is free to seal against the seal ring 20 attached to the spear connector 28.

However the spear connector 28 is no longer able to move axially outwardly away from the interior of the keg to an extent necessary for the seal ring 20 to contact the outer valve seat 32 of the housing 14, 50 the outer valve can no longer close. This is because the pawls 64 of the seal ring 20 have moved angularly to an extent necessary to engage under the wider portions 122 of the flange 118 of the collar 92, thus restraining outward axial movement of the spear connector 28. It will also be noted that the fifth detent position 116 is axially inward of the first and third detent positions 108 and 112, which also restricts outward axial movement of the spear connector 28.

It will be noted from Figures Ia, 5, 6, 7 and 8a that the pins 88 each have a faceted cross-section, with faces angled to promote the above-described navigation of the pins 88 along the convoluted slots of the cam gates 106 as the collar 92 turns, driven by reciprocal axial movement of the pins 88.

The mechanism of the invention ensures that the keg cannot be left pressurised after use and also that it cannot be refilled with the closure being re-closed afterwards. As noted above, the mechanism of the invention does not suffer from the long tolerance chains of US 4909289 or the inability of US 4909289 to handle the variety of filling heads and dispense heads that are on the market. Also, unlike DE 10 2007 036 469, the mechanism of the invention can be used even if the filling stroke is equal to or longer than the dispense stroke.

Beneficially, the mechanism of the invention allows particularly accurate control of the gap that remains between the seal ring 20 and the outer valve seat 32 after dispensing. This allows the rate of outward pressure-equalising gas flow to be controlled effectively.

Claims

Claims 1. A closure for a pressure vessel such as a keg, the closure comprising: a housing; at least one valve element that is movable along an axis with respect to the housing into closed and open states; and a lock mechanism that is capable of holding the valve element in the open state; wherein the lock mechanism comprises a locking element that is coupled to the valve element to move in a direction transverse to said axis in response to said movement of the valve element, the locking element being movable between an unlocked position in which the valve element can attain the closed state and a locked position in which the valve element is held in the open state.
2. The closure of Claim 1, wherein a cam mechanism acts between the valve element and the locking element to convert axial movement of the valve member into transverse movement of the locking element.
3. The closure of Claim 2, wherein the cam mechanism comprises a cam path associated with one of the valve element and the locking element and a drive element associated with the other of the valve element and the locking element, relative movement between the drive element and the cam path converting axial movement of the valve member into transverse movement of the locking element.
4. The closure of Claim 3, wherein the drive element is associated with the valve element and the cam path is associated with the locking element, and the drive element moves generally parallel to said axis to drive transverse movement of the locking element by virtue of relative movement between the drive element and the path.
5. The closure of Claim 4, wherein the cam path comprises a succession of detent positions for the drive element, successive detent positions being spaced parallel to said axis.
6. The closure of Claim 5, wherein successive detent positions of the cam path are spaced in a direction transverse to said axis.
7. The closure of Claim 5 or Claim 6 and being arranged for reciprocal movement of the valve element along the axis, wherein successive detent positions of the cam path alternate between axially inward and axially outward positions with respect to the pressure vessel.
8. The closure of Claim 7, wherein the locked position corresponds to an axially outward detent position that extends outwardly to a lesser extent than a previous axially outward detent position of said succession.
9. The closure of any of Claims 5 to 8, wherein the cam path comprises, in succession: a first detent position in which the valve element may adopt the closed state; a second detent position in which the valve element may adopt the open state; a third detent position in which the valve element may adopt the closed state; a fourth detent position in which the valve element may adopt the open state; and a fifth detent position in which the locking element is in the locked position and the valve element is held in the open state.
10. The closure of any preceding claim, wherein the locking element turns about said axis between the unlocked position and the locked position.
11. The closure of Claim 10, wherein the locking element is a collar that encircles the valve element.
12. The closure of any preceding claim, wherein a pawl movable with the valve element is aligned with a lock formation of the locking element by virtue of said transverse movement of the locking element into the locked position.
13. The closure of Claim 12, wherein the lock formation is disposed axially outwardly of the pawl when the locking element is in the locked position.
14. The closure of Claim 12 or Claim 13, wherein the lock formation of the locking element is transversely displaced with respect to the pawl when the locking element is in the unlocked position, whereby the pawl may bypass the lock formation.
15. A pressure vessel such as a keg, fitted with the closure of any preceding claim.