GB2158906A

GB2158906A - Valve closure for kegs

Info

Publication number: GB2158906A
Application number: GB08412810A
Authority: GB
Inventors: Bernt Ipsen
Original assignee: Micro Matic AS
Current assignee: Micro Matic AS
Priority date: 1984-05-18
Filing date: 1984-05-18
Publication date: 1985-11-20
Also published as: GB2158906B; GB8412810D0

Abstract

A failsafe system for incorporating a beer keg valve 6 within a beer keg neck 48 comprises arranged a valve body 10 having an outwardly facing helical groove 100 defining a female screw thread which cooperates with an inwardly directed pin 110 in the neck. Once inserted the valve body is rotated, the pin riding on the groove causing the body to be drawn downward into the neck. A semicircular notch 104 in the groove acts as a safety slot to receive 110 if the valve body is removed with the keg still under pressure, the internal pressure being safely vented via 100 and slot 102. <IMAGE>

Description

SPECIFICATION Beer keg valve systems This invention relates to beer keg valve systems. For the dispensing of beer under pressure from beer kegs, it is now usual to employ a dispenser head or coupler which is secured to a keg neck in which a valve assembly is located. Operation of the coupler is arranged to open two valves in the valve assembly to communicate carbon dioxide under pressure to the top of the beer in the keg, and to communicate another part of the valve assembly, which is normally immersed in the beer, to another passage in the coupler which in turn is connected by a suitable hose to the region in which the beer is to be dispensed.

It has been found that there is an inherent danger with some of these systems in that, if unauthorised or inadvertent attempts are made to remove the valve assembly from the keg neck, while the keg is still under pressure, in some circumstances the valve assembly can be bodily ejected causing physical injury.

A proposal to alleviate this problem is outlined in U.S. Patent Specification 4181143 (Fallon) which suggests the use of a generally Z shaped slot in a keg neck which cooperates with an outwardly extending pin on the valve assembly.

It is believed however that improvement can be effected over that proposal particularly in order to achieve extremely quick venting of the keg if attempts are made to remove the valve assembly. For example in the Fallon arrangement there is no specific venting path provided, and the seal between the valve assembly and keg neck in this arrangement tends to be forced outwards and blocks venting of gas between the parts.

The invention has various aspects of which the following are some, but not necessarily all: According to one aspect a beer keg valve system comprises a keg neck having an inwardly facing wall, a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position with respect to the keg neck, one of said inwardly and outwardly facing walls having a female screw thread formed therein which extends to a substantial extent around the circumference of the wall from an upper region of the wall to a lower region of the wall, and the other of said inwardly and outwardly facing walls having an abutment of short circumferential extent protruding thereform and which is receivable in said female screw thread and cooperates therewith such that full insertion of the valve assembly into its operative position with respect to the keg neck necessitates at least partial rotation of the valve assembly with respect to the keg neck and travelofthe abutment from said upper region to said lower region.

Conveniently the upper end ofthe female screw thread is open-topped thereby to communicate with atmosphere externally of the system and to allow venting of gas from the keg via the screw thread on commencement of release of the valve assembly from its operative position with respect to the keg neck if the keg is under pressure. The lower end of the female screw thread may be arranged to be placed in communication with the interior of the keg after only limited displacement of the valve assembly outwardly of the keg neck from said operative position to permit full venting of the keg via the screw thread. In this case the abutment and the screw thread may be of such relative dimensions that the abutment does not fully obstruct the screw thread at any time.

To facilitate assembly of the parts the upper end of the screw thread may have a generally vertical portion in which the abutment is received in the operative position of the valve assembly with respect to the keg neck thereby, at that time, to prevent rotation of the valve assembly within the keg neck. Preferably the generally vertical portion of the screw thread is open-topped to permit venting therefrom.

A retainer may be included which is insertable after the valve assembly is in its operative position with respect to the keg neck, the said retainer preventing movement of the valve assembly out of the keg neck. The keg neck and valve assembly, in said operative position, may have vertically aligned and horizontally spaced sealing surfaces between which an annular radial seal is a force fit, the annuial seal, in the operative position, not being under axial compression.With this construction, it may be arranged that removal of said retainer initially permits slight axial movement of the valve assembly out of the keg neck and separates said sealing surfaces in an axial direction to a sufficient extent that the annular seal is no longer in contact with both of said sealing surfaces, thereby to permit gaseous communication between the interior of the keg, around the seal, to the lower end of the screw thread.

In order further to ensure inadvertent release a safety recess may be formed in a portion of one wall of said screw thread, the safety recess being dimensioned and positioned with respect to the abutment such that any attempt to release the valve assembly by unscrewing thereof whilst the keg is under pressure causes the valve assembly to be moved outwardly and to force said one wall of the screw thread against the abutment, whereby, on rotary alignment of the abutment and the safety recess, the abutment is automatically moved into the recess by the keg pressure, and thereafter prevents further rotation of the valve assembly with respect to the keg neck until relative axial movement of the valve assembly and keg neck in the opposite direction releases the abutment from the recess.

According to a further aspect of the invention, a beer keg valve system comprising a keg neck having an inwardly facing wall and a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position within the keg neck, said outwardly facing wall of the valve assembly having a female screw thread formed therein which extends from an upper region of said outwardly facing wall to a lower region thereof, the inwardly facing wall of the keg neck having an abutment protruding inwardly therefrom, the abutment being receivable in said female screw thread on initial insertion of the valve assembly into the keg neck and cooperating with the screw thread during subsequent rotation of the valve assembly with respect to the keg neck thereby to draw the valve assembly into the keg neck into its operative position with respect thereto.Conveniently the valve assembly and abutment undergo approximately 270 of relative rotation between initial insertion of the valve assembly and adoption of said operative position. The female screw thread may have an open lower edge to allow the abutment to enter the lower end of the screw thread.

According to another aspect of the invention a beer keg valve system comprises a keg neck and a valve assembly which is insertable into the keg neck into an operative position with respect thereto at which time the keg neck and valve assembly have vertically aligned but horizontally spaced annular substantially vertical sealing surfaces, and an annular resilient seal positioned between and in engagement with each of the vertical sealing surfaces, the entire underside of the annular seal in the operative position of the valve assembly being in open communication with the interior of the keg thereby to be subjected to the gaseous pressure therein. The valve assembly may have a further substantially horizontal, downwardly facing annular surface thereon and against which the annular seal is upwardly forced by gaseous pressure within the keg.

The interior of the keg neck, immediately above its generally vertical sealing surface, may have an annulus of greater diameter than the generally vertical sealing surface thereof and the arrangement being such that initial axial relative movement of the valve assembly out of the keg neck away from said operative position causes the annular seal to be vertically aligned with the annulus thereby to place the interior of the keg in communication with the annulus and in communication with a gas venting passage extending from the annulus through one or both of or between the keg and valve assembly.

Preferably the gas venting passage comprises a female screw thread on one of an internal wall of the keg neck and an external wall of the valve assembly, the screw thread cooperating with an abutment projecting from the other of the internal and external walls, the dimensions of the abutment and the screw thread being such that the abutment at no time blocks the screw thread against venting of gas upwardly therethrough.

The annulus may be at least partially defined byan upper generally vertical annular wall portion in the keg neck and a lower inwardly and downwardly tapered annular wall portion in the keg neck the lower end of the lower wall portion merging with the sealing surface of the keg neck.

According to yet another aspect of the present invention a beer keg valve system comprises a keg neck, a valve assembly which is insertable into the keg neck into an operative position in which an annular radial seal is sealing located between generally vertical annular sealing surfaces on the keg neck and the valve assembly, retaining means being provided which prevents direct vertical outward movement of thevalve assembly from the operative position, and the annular seal, in the said operative position, not being under axial compression.

The retaining means may be at least partially provided by a female screw thread formed on one of the keg neck and the valve assembly and a radially extending abutment cooperating with the screw thread and formed on the other of the keg neck and the valve assembly, and further positive retaining means may be included which is insertable into and removable from a retaining position in which it prevents axial or rotational movement of the valve assembly with respect to the keg neck. The further retaining means may comprise a C clip retainer receivable in an annular recess formed in an internally facing wall of the keg neck, the valve assembly having an upper end which abuts the underside of the C clip when the valve assembly is in the operative position.

According to another aspect of the present invention a beer keg valve system may have an inwardly facing wall, a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position with respect to the keg neck, one of said inwardly and outwardly facing walls having a tortuous groove formed therein which extends to a substantial extent around the circumference of the wall from an upper region of the wall to a lower region of the wall, and the other of said inwardly and outwardly facing walls having an abutment of short circumferential extent protruding therefrom which is receivable in said tortuous groove without at any time blocking gaseous venting therethrough, the abutment cooperating with the tortuous groove such that full insertion of the valve assembly into its operative position with respect to the keg neck necessitates at least partial rotation of the valve assembly with respect to the keg neck and travel of the abutment from said upper region to said lower region of the walls, the upper and lower ends of the tortuous groove each being open thereby to allow venting of gas from the keg via the tortuous groove on commencement of release of the valve assembly from the keg neck, and whilst the keg is under pressure.

The invention may be carried into practice in various ways but one specific embodiment will now be described, by way of example, with reference to the accompanying drdawings in which: Figure 1 shows, in perspective a valve assembly for a beer keg; Figure 2 shows in perspective, a cyclindrical neck which is welded into a keg opening and which receives the valve assembly of Figure 1; Figure 3 is a sectional side elevation of the valve assembly of Figure 1; Figure 4 shows a quarter cross section of the keg neck located on a keg; Figure 5 shows a side elevation of a valve body forming part of the valve assembly of Figures 1 -and 3; Figure 6 shows a development of the helical groove of the valve body; Figure 7 shows a plan view of a retaining C clip of the valve assembly;; Figure 8 shows a detailed scrap section of the valve assembly located within the keg neck, in a sealed position with the C clip in place; Figure 9 shows the same view as Figure 8 but with the C clip removed and the valve assembly located within the keg neck in a preliminary de-pressurisation position; Figure 10 shows the same view as Figures 8 and 9 but with the valve assembly partially rotated to a secondary de-pressurisation position; and Figure 11 shows the same view as Figures 8, 9 and 10 but with the valve assembled in the position in which it is inserted and removed from the keg neck.

The embodiment to be described comprises a beer keg valve system the purpose of which is to seal a beer keg under pressure and to allow connection to the assembly of a coupler by which the beer is dispensed from the keg.

Thus Figures 2 and 4 illustrate a keg neck 48, usually manufactured of stainless steel, and which, as shown in Figure 4 is welded into an opening 52 in the upper end of a beer keg 80.

As will be described, the keg neck 48 is arranged to cooperate with a valve assembly 6 of the type shown in Figures 1 and 3 and which will also be described in detail. Briefly, the valve assembly of Figures 1 and 3 can be inserted into the keg neck 48 from above and, by rotating the valve assembly about its axis for approximately one full turn, it is arranged that the keg neck receives the valve assembly in a sealed operative position in which the valve assembly is retained by a retainer or C ring 58 of the form shown in Figure 7.

When the valve assembly 6 is fully located and retained in the keg neck 48, which will usually take place in the brewery, the keg can be charged with beer and the valve arrangement of the valve assembly will normally be spring biassed to a closed position to retain the beer under pressure within the keg.

The upper end of the valve assembly 6 is arranged to receive the lower end of a coupler (not shown) of conventional form, and which, when correctly secured to the valve assembly and actuated, will open a pair of valves shown in Figure 3, one valve permitting introduction of carbon dioxide into the keg under pressure, via the coupler, to pressurize the keg, and the other valve permitting the passage of the beer from the keg via the coupler to the point at which the beer is to be dispensed, for example in a bar.

The various parts will now be described in more detail.

Referring to Figure 3, the valve assembly includes a valve body 10 of annular form which is arranged to be coupled to the keg neck 48, and to the lower end of which is welded a cup 12, again of generally annular form, and having four symetrically disposed trapezium-shaped apertures 14.

In its interior the valve body 10 has an annular downwardly facing tapered valve surface forminga seat 1 6 for an outer gas valve formed by a rubber valve member 1 8 which, when engaged with the valve seat 1 6 closes this valve. The valve member 1 8 is biassed upwards to close this gas valve by an outer gas-valve spring 20 which acts between an out-turned flange 22 on the upper end of a syphon tube 24 in which the valve member 1 8 is located. The lower end of the outer gasvalve spring 20 acts against an abutment ring 26 located in the lower end of the cup 1 2 and held in place by three lugs 28 which project inwardly and horizontally from the lower end of the cup 12.

The rubber valve member 1 8 has an internal reinforcing metal ring 30, and the rubber valve member 1 8 is located as a force-fit in the upper end of the syphon tube 24 and moves with it as a unit.

The second valve provided by the valve assembly comprises an inner or beer valve formed by a metal valve member 34 having a tapered upper face 36 which seats against an annular surface 35 at the lower end of the rubber valve member 1 8. The valve member has three equally spaced vertical legs 37, the lower ends of which bear on the upper end of an inner beer-valve spring 40, the lower end of which acts on an inward step or shoulder 42 in the syphon tube 24. 8elow the shoulder 42, the syphon tube 24 is arranged to extend vertically downards to adjacent the bottom of the beer keg, when the valve assembly is fully located and retained in the keg neck 48.

The valve body 10 has a complex external contour, commencing at its lower end immediately adjacent the upper end of the cup 12, with a downwardly facing horizontal step 1 3 below which is positioned a relatively hard 0ring seal 44. As will be described, the horizontal step 13, whilst it may be engaged by the O-ring 44 when biassed upwardly by internal pressure within the keg, does not form an essential sealing surface against release of pressure within the keg. Sealing essentially takes place betwen vertical surfaces with which the 0 ring 44 engages, one of which 1 9 is the external upper end of the cup 12 against which the 0 ring 44 is in tight engagement as shown in Figure 3.

Immediately above the horizontal step 1 3 the external contour of the valve body has a vertical surface 21, seen most clearly in Figure 1, and also on the right hand side of Figure 3 and the left hand side of Figure 1 0.

It is to be noted that the diameter of the vertical surface 21 is little more than the external diameter of the 0 ring seal 44 and as will be apparent, in certain relative positions of the valve assembly and the keg neck this ensures a good clearance between the internal surface of the keg neck and the valve body to permit quick degassing or venting of the keg in certain circumstances.

Immediately above the vertical surface 21 of the valve body, over a major part of its circumference, there is an upwardly and outwardly tapered face 15, again best shown in Figures 1,3 and 10.

Above the tapered face 15, the external contour of the valve body is generally vertical and cylindrical but this cylindrical surface contains an outwardly facing helical groove 100 which defines a female screw thread best seen in Figures 1, 5 and 6, but which also appears in each of the sections of Figures 3, 8, 9, 10 and 11. The lower end 1 00A of the helical groove 100, as shown in Figure 1 and Figure 5, commences just above the lower vertical face 21 of the valve body and this region of the groove cuts across the tapered face 15, so that in this region the tapered face 1 5 is not present, and in fact the lower end IOOA of the groove has no lower edge.When the valve assembly is lowered into the keg neck 48, an inwardly directed pin 110, shown for example in Figure 2, will thus be able to pass into the lower end 1 00A of the groove 100, assuming, of course, that the valve assembly is in the correct rotational position for this purpose.

Once the pin 110 is received in the lower end of the groove 100, the valve assembly can be rotated within the keg neck at which time the pin, being stationary, will cause the valve assembly to be drawn downwardly into the keg neck. It is to be stressed that the lower end 1 0OA of the groove 100, which has an open lower edge in order to receive the pin 110, is of limited circumferential extent, for example approximately 100" of the circumference of the valve body. The developed view of the helical groove 100, shown in figure 6, illustrates this feature.

Thus above the point 1 00B which represents the upper limit of the open-bottomed lower end 1 00A of the groove 100, the groove is effectively a full female screw thread having generally horizontal upper and lower faces against which the pin 110 can ride. The upper end of the groove 100 terminates, via a curved corner 100C, shown clearly in Figures 1, 5 and 6, with a short vertical open-ended slot 102 in which the pin 110 is received (as shown in Figures 8 and 9) when full rotation of the valve assembly with respect to the keg neck has taken place. The width of the groove 100 between its upper and lower horizontal surfaces is approximately 6.0 mm whereas the diameter of the pin 110 is slightly less i.e.

4.5 mm. Thus at any time when the pin 110 is riding in the groove 100, for example during removal of the valve assembly from the keg neck, there will be quite a substantial clearance between the pin 110 and the groove 100. In the event that attempts are made to remove the valve assembly whilst the keg is still under pressure this will permit venting of the keg up the groove 100, past the pin 110, and out the top of the vertical slot 102.

At a position a short way down the groove 100 from the vertical slot 102, the lower edge of the groove 100 is provided with a semi-circular notch 104 which serves as a safety slot to receive the pin 110 in a manner to be described later.

Referring now to the keg neck 48 in more detail, this has a vertical cross section which, apart from the presence of the inwardly extending pin 110, is constant throughout the circumference of the neck. Thus, referring for example to Figure 4, the main body of the keg neck forms a cylindrical vertical wall 50, the lower external extremity of which has a downwardly facing recess 52 for engagement with an aperture in the keg 80 to which the keg neck is welded. The upper end of the vertical wall 50 has an outwardly extending bead 54 and, within this bead, the inner wall of the neck is provided with an annular groove 56 into which the C clip or retainer 58 of Figure 7 can be inserted to mainrain the valve assembly complete, in the manner shown in Figure 8.

As shown in Figure 4, the lower end of the vertical wall 50 of the keg neck, has an inwardly and downwardly tapered section 59 merging with a vertical wall 60 which in turn terminates in an upwardly facing horizontal step 62. As shown in Figure 8, on assembly of the valve assembly and neck the step 62 is positioned below the 0 ring seal 44 but does not in practice form a sealing surface engaging this 0 ring. It is to be noted that the vertical wall 60 of the keg neck, when the valve assembly is fully inserted, is vertically aligned with the vertical surface 1 2A formed on the upper end of the cup 1 2 and which receives the 0 ring seal 44.The dimensions of the parts are carefully designed in this region in relation to the dimensions and resilient characteristics of the 0 ring seal 44 to ensure that the 0 ring is a force-fit with the vertical surface on the neck 60 and 1 2A on the cup in order to provide an adequate seal to retain the beer under pressure within the keg. It is to be noted from Figure 8 that the vertical wall 60, at its point where it merges with the tapered section 59, is slightly spaced from the lower external corner of the valve body in the region of the inward step 13, so that there is no mechanical or metal-to-metal engagement between the parts when fully assembled as shown in Figure 8.

As shown in Figure 8, the seal 44, in the fully inserted position of the valve assembly, lies in a space provided between the downwardly facing inward step 13, of the valve body 10 and the upwardly extending step 62 of the keg neck 48, but the dimensions are such that the insertion of the C clip retainer 58 does not necessitate or cause compression in an axial sense of the 0 ring seal 44.

Rather, as has been described, the 0 ring seal 44 is only a radial fit between the vertical annular walls 1 2A and 60 of the valve body 10 and the keg neck 48 respectively. Thus a clearance 1 38 is usually maintained below the O ring seal 44, in the manner shown in Figure 8, and there will be a certain amount of lost motion in that the valve assembly 6 can move up and down slightly because of this clearance when there is no pressure within the keg. When the keg 80 is under pressure, the pressure below the 0 ring seal 44 tends to force the valve assembly 6 upwardly against the C clip 58, so forcing the 0 ring seal against the downwardly facing inward step 1 3 of the valve body and slightly distorting the seal 44 to cause it to press firmly against the vertical walls with which it engages.On its inner periphery the seal 44 provides a primary seal against the vertical face 1 2A of the cup and a secondary seal against the downwardly facing surface 1 3. On the outer periphery of the 0 ring seal 44 there is a single seal provided between the 0 ring seal and the wall 60 of the keg neck 48. By virtue of this arrangement, and the fact that there is no compression of the 0 ring seal in an axial sense, there is no particular criticality in the dimensions of the keg neck and valve body as regards the faces 62 and 1 3 and thus the vertical positioning of the valve body in the keg neck is not critical so long as adequate alignment occurs between the vertical surfaces 60 and 1 2A which are engaged by the 0 ring seal 44.

When the valve assembly is to be inserted into tne keg neck, it is simply dropped in and rotated to the position of Figure 11 when the pin 110 in the keg neck is aligned with the open lower side of the lower portion of the screw thread 1 00. The pin is then aligned with and receivable in the remainder of the thread 100. The valve assembly is then rotated through a further approximately 270 until the pin reaches the top of the screw thread and enters the lower end of the vertical slot 102 as shown in Figure 9. Following this, the valve assembly can be moved axially downards to its operative position of Figure 8, in which the 0 ring seal 44 is firmly received between its vertical sealing surfaces 1 2A and 60.The C clip retainer 58 of Figure 7 can then be inserted into the annular groove 56, to achieve the completed system of Figure 8.

Assuming the keg is not under pressure, removal of the valve assembly from the keg neck is achieved, firstly, by removal of the C clip retainer, lifting the valve assembly slightly to bring the pin 110 into the lower end of the slot 102, and unscrewing the valve assembly.

This is an extremely simple operation and does not involve any relative rotation of the seal 44 with respect to the keg neck, so avoiding any wear of the seal.

In the event that an attempt is made to remove the valve assembly while the keg is under pressure, as soon as the C clip 58 is removed, the gaseous pressure within the keg will eject the valve assembly slightly until it reaches the position of Figure 7 at which the pin 110 hits the lower end of the slot 102 and prevents further ejection. In the Figure 7 position the 0 ring seal 44 has lifted clear of its sealing surface 60 on the keg neck, and the interior of the keg is now free to vent into the annulus formed by the tapered wall 59, and thence into the screw thread 100. The gas now has a free passage up the screw thread and out of the system via the slot 102.

In the normal way therefore, the keg can vent within a few seconds and remove any further danger of the valve assembly being ejected from the keg.

In the unlikely event that the operator attempts to rotate the valve assembly to unscrew it from the keg neck (which in itself is an unnatural operation, since the screw thread is left-handed), any continued gaseous pressure in the keg will ensure that the lower edge of the slot 100 is forced against the pin 110.

Thus the pin will engage in the safety recess 104, as shown in Figure 10 and prevent further rotation of the valve assembly until full venting has taken place.

Claims

A1.A beer keg valve system comprising a keg neck having an inwardly facing wall, a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position with respect to the keg neck, one ofsaid inwardly and outwardly facing walls having a female screw thread formed therein which extends to a substantial extent around the circumference of the wall from an upper region of the wall to a lower region of the wall, and the other of said inwardly and outwardly facing walls having an abutment of short circumferential extent protruding therefrom and which is receivable in said female screw thread and cooperates therewith such that full insertion of the valve assembly into its operative position with respect to the keg neck necessitates at least partial rotation of the valve assembly with respect to the keg neck and travel of the abutment from said upper region to said lower region.

A2. A valve system as claimed in claim Al in which the upper end of the female screw thread is open-topped thereby to communicate with atmosphere externally of the system and to allow venting of gas from the keg via the screw thread on commencement of release of the valve assembly from its operative position with respect to the keg neck if the keg is under pressure.

A3. A valve system as claimed in claim A2 in which the lower end of the female screw thread is arranged to be placed in communication with the interior of the keg after only limited displacement of the valve assembly outwardly of the keg neck from said operative position to permit full venting of the keg via the screw thread.

A4. A system as claimed in claim A3 in which the abutment and the screw thread are of such relative dimensions that the abutment does not fully obstruct the screw thread at any time.

A5. A system as claimed in any one of claims Al to A4 in which the upper end of the screw thread has a generally vertical portion in which the abutment is received in the operative position of the valve assembly with respect to the keg neck thereby, at that time, to prevent rotation of the valve assembly within the keg neck.

A6. A system as claimed in claim A5 in which the said generally vertical portion of the screw thread is open-topped to permit venting therefrom.

A7. A system as claimed in claim A5 including a retainer which is insertable after the valve assembly is in its operative position with respect to the keg neck, the said retainer preventing movement of the valve assembly out of the keg neck.

A8. A system as claimed in claim A7 in which the keg neck and valve assembly, in said operative position, have vertically aligned and horizontally spaced sealing surfaces between which an annular radial seal is a force fit, the annular seal in the operative position, not being under axial compression.

A9. A system as claimed in claim A8 wherein removal of said retainer initially permits slight axial movement of the valve assembly out of the keg neck and separates said sealing surfaces in an axial direction to a sufficient extent that the annular seal is no longer in contact with both of said sealing surfaces, thereby to permit gaseous communication between the interior of the keg, around the seal, to the lower end of the screw thread.

A10. A system as claimed in any one of the preceding claims Al to A9 including a safety recess formed in a portion of one wall of said screw thread, the safety recess being dimensioned and positioned with respect to the abutment such that any attempt to release the valve assembly by unscrewing thereof whilst the keg is under pressure causes the valve assembly to be moved outwardly and to force said one wall of the screw thread against the abutment, whereby, on rotary alignment of the abutment and the safety recess, the abutment is automatically moved into the recess by the keg pressure, and thereafter prevents further rotation of the valve assembly with respect to the keg neck until relative axial movement of the valve assembly and keg neck in the opposite direction releases the abutment from the recess.

B1. A beer keg valve system comprising a keg neck having an inwardly facing wall and a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position within the keg neck, said outwardly facing wall of the valve assembly having a female screw thread formed therein which extends from an upper region of said outwardly facing wall to a lower region thereof the inwardly facing wall of the keg neck having an abutment protruding inwardly therefrom, the abutment being receivable in said female screw thread on initial insertion of the valve assembly into the keg neck and cooperating with the screw thread during subsequent rotation of the valve assembly with respect to the keg neck thereby to draw the valve assembly into the keg neck into its operative position with respect thereto.

B2. A system as claimed in claim B1 in which the valve assembly and abutment undergo approximately 270 of relative rotation between initial insertion of the valve assembly and adoption of said operative position.

B3. A system as claimed in claim B1 or claim 82 in which the lower end of the female screw thread has an open lower edge to allow the abutment to enter the lower end of the screw thread.

C1. A beer keg valve system comprising a keg neck and a valve assembly which is insertable into the keg neck into an operative position with respect thereto at which time the keg neck and valve assembly have vertically aligned but horizontally spaced annular substantially vertical sealing surfaces, and an annular resilient seal positioned between and in engagement with each of the vertical sealing surfaces, the entire underside of the annular seal in the operative position of the valve assembly being in open communication with the interior of the keg thereby to be subjected to the gaseous pressure therein.

C2. A system as claimed in claim C1 in which the valve assembly has a further, substantially horizontal, downwardly facing annular surface thereon and against which the annular seal is upwardly forced by gaseous pressure within the keg.

C3. A system as claimed in claim C1 or claim C2 in which the interior of the keg neck, immediately above its generally vertical sealing surface, has an annulus of greater diameter than the generally vertical sealing surface thereof and the arrangement being such that initial axial relative movement of the valve assembly out of the keg neck away from said operative position causes the annular seal to be vertically aligned with the annulus thereby to place the interior of the keg in communication with the annulus and in communication with a gas venting passage extending from the annulus through one or both of or between the keg and valve assembly.

C4. A system as claimed in claim C3 in which the gas venting passage comprises a female screw thread on one of an internal wall of the keg neck and an external wall of the valve assembly, the screw thread cooperating with an abutment projecting from the other of the internal and external walls, the dimensions of the abutment and the screw thread being such that the abutment at no time blocks the screw thread against venting of gas upwardly therethrough.

C5. A system as claimed in claim C3 in which the annulus is at least partially defined by an upper generally vertical annular wall portion in the keg neck and a lower inwardly and downwardly tapered annular wall portion in the keg neck the lower end of the lower wall portion merging with the sealing surface of the keg neck.

D1. A beer keg valve system comprising a keg neck, a valve assembly which is insertable into the keg neck into an operative position in which an annular radial seal is sealing located between generally vertical annular sealing surfaces on the keg neck and the valve assembly, retaining means being provided which prevents direct vertical outward movement of the valve assembly from the operative position, and the annular seal, in the said operative position, not being under axial compression.

D2. A system as claimed in claim D1 in which the retaining means is at least partially provided by a female screw thread formed on one of the keg neck and the valve assembly and a radially extending abutment cooperating with the screw thread and formed on the other of the keg neck and the valve assembly.

D3. A system as claimed in claim D2 including further positive retaining means insertable into and removable from a retaining position in which it prevents axial or rotational movement of the valve assembly with respect to the keg neck.

D4. A system as claimed in claim D3 in which the further retaining means comprises a C clip retainer receivable in an annular recess formed in an internally facing wall of the keg neck, the valve assembly having an upper end which abuts the underside of the C clip when the valve assembly is in the operative position.

El. A beer keg valve system comprising a keg neck having an inwardly facing wall, a valve assembly having an outwardly facing wall, the valve assembly being insertable into an operative position with respect to the keg neck, one of said inwardly and outwardly facing walls having a tortuous groove formed therein which extends to a substantial extent around the circumference of the wall from an upper region of the wall to a lower region of the wall, and the other of said inwardly and outwardly facing walls having an abutment of short circumferential extent protruding therefrom which is receivable in said tortuous groove without at any time blocking gaseous venting therethrough, the abutment cooperating with the tortuous groove such that full insertion of the valve assembly into its operative position with respect to the keg neck necessitates at least partial rotation of the valve assembly with respect to the keg neck and travel of the abutment from said upper region to said lower region of the walls, the upper and lower ends of the tortuous groove each being open thereby to allow venting of gas from the keg via the tortuous groove on commencement of release of the valve assembly from the keg neck, and whilst the keg is under pressure.