Abstract:
The compressed CO 2  gas source is an insert that can be fixed in a sealed manner in an opening of the vessel. The insert has a high-pressure CO 2  cartridge, a pressure-regulating valve for discharging CO 2  therefrom and a control element that is accessible from the outside and that can be actuated to pierce the high-pressure CO 2  cartridge. The control element can be automatically interlocked and blocked against further actuation after it has first been actuated.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a vessel that can be filled with liquid and closed in pressure-tight condition, and from which liquid can be withdrawn. Examples of such vessels are drums, small drums (party kegs) or cans, in which CO 2 -containing liquids, especially beverages, are filled under pressure. In particular, it relates to party beer kegs. 
     2. Description of Related Art 
     There exist tap fittings that operate with high-pressure CO 2  cartridges and that can be used to tap such vessels in order to withdraw liquid therefrom by means of CO 2  pressure. This corresponds to the standard tapping technique in gastronomy, wherein CO 2  from high-pressure CO 2  bottles is used and very good wholesomeness and shelf life of the beer are achieved. 
     In some consumer groups, however, tap fittings with CO 2  high-pressure cartridges have not become popular. For persons who buy party beer kegs only occasionally, it is not worthwhile to procure an expensive tap fitting. Some people are even uncomfortable handling high-pressure CO 2  cartridges. Others worry about the replacement supply of cartridges. 
     There have therefore been developed party beer kegs equipped with an integrated outlet tap in the bottom region of the keg, whereby the beer can be drawn by the internal pressure and gravity alone. Usually air is admitted to the party keg above the liquid surface therein, in order to permit pressure equalization. This can be achieved by puncturing with a can opener. However, other party beer kegs have an integrated outlet tap and a hand-operated air-admission valve in the top end plate of the keg, forming part of a bunghole closure (see WO 99/23008 A1). 
     A disadvantage of such party kegs is that the wholesomeness and shelf life of the beer are impaired by the ingress of air into the top space of the keg. When a party keg of this type is tapped, the contents must be consumed quickly, so that the beer does not become flat and stale. 
     Several suggestions have been made as regards improving the shelf life of beer in a tapped party keg. For example, WO 99/47451 A1 teaches integrating an aerosol can that contains CO 2  bound to active carbon under low pressure into the party keg and building up a CO 2  pressure in the top space of the keg sufficient to equal or exceed the partial pressure of the CO 2  dissolved in the beer. A disadvantage is the large volume of the can. Furthermore, active carbon is a very expensive storage medium. 
     From DE 19952379 A1 there is known a CO 2  dispenser for party kegs in the form of a separate manual device, with which the party keg is pierced above the liquid surface therein in order to pump CO 2  into the top space of the keg. The dispenser contains a high-pressure CO 2  cartridge and a pressure-regulating valve. It is intended for multiple uses and can be transferred from party keg to party keg. Even if the CO 2  consumption may be smaller than in the case of a tap fitting operating with CO 2 , such a CO 2  dispenser ultimately raises similar concerns in consumer groups. 
     From practice it is also known that there can be introduced into the top space of a party beer keg a pressure bag, which expands when the pressure in the top space drops, thereby on the one hand filling the empty space being formed and on the other hand exerting a contact pressure on the liquid surface in the keg greater than the partial pressure of the CO 2  dissolved in the beer. The pressure bag comprises multiple plies of plastic film that is impermeable to oxygen diffusion. It has a plurality of chambers that contain gas-forming chemicals, such as baking powder and citric acid. The chambers are successively activated as the pressure drops in the top space of the party keg and are inflated by the gas evolved during the reaction of the chemicals. 
     A disadvantage of the known pressure bag is the unsteady application of pressure on the beer. The pressure rises suddenly when the respective next chamber of the pressure bag is activated, and it then drops successively. This results in irregular tap behavior. The tap behavior fluctuates between discharge of the beer in a strong stream and a mere trickle. 
     The starting point of European Patent Application No. 05011896.7 is to provide a vessel of the type mentioned hereinabove having an integrated compressed CO 2  gas source of small overall volume, from which discharged CO 2  exerts a steady pressure on the liquid in the vessel and improves its shelf life and wholesomeness. The vessel has an insert that can be fixed in sealed manner in an opening of the vessel and a high-pressure CO 2  cartridge, a pressure-regulating valve for discharging CO 2  therefrom and a control element that is accessible from the outside and that can be actuated to pierce the high-pressure CO 2  cartridge with a piercing needle. 
     By virtue of its small overall volume, the insert is suitable for replacing the bunghole closure with pressure-equalizing valve according to WO 99/23008 A1, without necessitating any substantial modifications to the shape and size of the respective vessel to be equipped therewith, such as a party beer keg. The processes at a filling plant are altered slightly at most. The insert can be made of plastic materials, which for years have proved most suitable for a bunghole closure with pressure-equalizing valve and an outlet tap. The operation of the compressed CO 2  gas source can be designed such that a user familiar with actuation of a conventional pressure-equalizing valve hardly notices any difference. The user does not directly handle a high-pressure CO 2  cartridge, which would probably make him uncomfortable. The cartridge is designed for one-time use in a single vessel and will be disposed of together therewith. In particular, the shelf life of beer in a tapped party keg will be extended by several days without concern by filling the top space with CO 2  instead of air. 
     Commercial pierceable CO 2  cartridges in a size suitable for the compressed CO 2  gas source contain approximately 16 g of CO 2  at a pressure of approximately 80 bar. The reduction and precise regulation of the pressure of the CO 2  discharged into the top space of the vessel imposes considerable requirements on the construction of a compressed CO 2  gas source in the form of a compact insert. The pressure is typically between 0.5 and 0.9 bar. It is equal to or slightly higher than the partial pressure of the CO 2  dissolved in the liquid. 
     Especially for beer, the CO 2  content is one of the factors that determines the taste. The CO 2  content varies from beer variety to beer variety. If the CO 2  pressure in the top space of the party keg is too low, CO 2  escapes from the beer. If the CO 2  pressure in the top space is too high, the beer becomes overcarbonated and its taste and wholesomeness are impaired. The compressed CO 2  gas source described in European Patent Application No. 05011896.7 ensures that neither one nor the other occurs. 
     In the vessel according to European Patent Application No. 05011896.7, the control element actuated to pierce the high-pressure CO 2  cartridge is a rotary knob, which cooperates with an axially guided slide used to actuate a piercing needle. The piercing needle is structurally combined with a valve element of the pressure-regulating valve. Its regulating function may be adversely affected if the user actuates the rotary knob once again. Certainly this is completely undesirable, but in the vessel according to European Patent Application No. 05011896.7 it is not precluded. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the invention is to secure the vessel known from European Patent Application No. 05011896.7 against manipulations of the control element of the insert, so that the regulating function of the pressure-regulating valve cannot be affected. 
     This object is achieved in that the control element of the insert can be automatically interlocked and blocked against further actuation after it has first been actuated. 
     In a preferred embodiment, the control element is a rotary knob that cooperates with an axially guided slide, which can be used to actuate a piercing needle for piercing the high-pressure CO 2  cartridge. The rotary knob is blocked by the slide. 
     In a preferred embodiment, the rotary knob is screwed forward against the slide, so that the slide is axially adjusted by turning the rotary knob. The piercing needle is driven axially by the slide. After a predetermined angle of rotation has been exceeded for piercing the high-pressure CO 2  cartridge, the slide springs back axially against the rotary knob. The slide snaps into the rotary knob and blocks it against further actuation. 
     In a preferred embodiment, the piercing needle is structurally combined with a valve member of the pressure-regulating valve, which is axially adjustable between a sealing position and a passing position at a valve seat of the pressure-regulating valve. The slide springs back when actuated by the piercing needle. 
     In a preferred embodiment, the slide comes into flush contact with the piercing needle during piercing of the high-pressure CO 2  cartridge, such that end face is against end face. 
     In a preferred embodiment, the piercing needle occupies a sealing position directly downstream from the valve seat of the pressure-regulating valve just before piercing takes place. Thereby the volume of the valve space to which the maximum pressure of the high-pressure CO 2  cartridge is admitted after it has been pierced is very small. 
     In a preferred embodiment, the vessel has a tightly sealed chamber, in which the head of the high-pressure CO 2  cartridge has a snug fit at the opening of the vessel. The tight seal of the chamber is preferred for hygiene reasons. 
     In a preferred embodiment, the high-pressure CO 2  cartridge is sealed against the wall of the chamber, around the circumference of its small diameter neck. Thereby the axial forces to which the cartridge is subjected during piercing are limited. 
     In a preferred embodiment, the insert occupies a top opening of the vessel. The CO 2  from the high-pressure CO 2  cartridge can be discharged not only into a top space of the vessel above the liquid surface therein, but also via a non-return valve directly into the liquid. 
     In a preferred embodiment, the opening that receives the insert is a bunghole, through which the vessel is filled with liquid. The insert functions as the bunghole closure. 
     The CO 2  from the high-pressure CO 2  cartridge can be discharged into the top space of the vessel above the liquid surface therein. However, it is also possible to connect a pressure bag to the insert. The pressure bag is pulled on by applying vacuum to the housing of the insert and is tightly heat-sealed to the housing. The pressure bag is ultimately disposed in direct contact with the housing of the insert in the interior of the vessel. It is inflated by the discharged CO 2 . Compared with the prior art pressure bag mentioned hereinabove, the advantage is then achieved that the filling pressure of the pressure bag is constant, or in other words no pressure fluctuations and irregularities in tapping behavior occur. The filling pressure can be set at a somewhat higher value than the partial pressure of the CO 2  dissolved in the liquid, which pressure therefore remains completely unaffected and neutral as regards taste. 
     In the variant with the pressure bag, a compressed gas other than CO 2  may also be injected from a high-pressure cartridge. 
     In a preferred embodiment, the vessel has an outlet tap at the bottom. Withdrawal of the liquid then takes place by internal pressure and the effect of gravity. The CO 2  from the high-pressure CO 2  cartridge prevents a reduced pressure from developing in the top space of the vessel. This is possible in the variants with and without pressure bag. 
     In the variant with the pressure bag, the vessel can have, instead of the outlet tap, a top spigot to which there leads a riser line extending to the bottom of the vessel. The liquid is conveyed by the pressure of the CO 2  discharged from the high-pressure CO 2  cartridge to the spigot. Tapping at the top of the vessel is more convenient than at the bottom. 
     In a preferred embodiment, an outlet spout together with a hose connection is provided on the outside of the spigot. The outlet spout is added to the vessel as a separate part. It is clipped onto the said vessel after the spigot has been removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail hereinafter on the basis of an exemplary embodiment illustrated in the drawings. 
         FIG. 1  shows a compressed CO 2  gas source in longitudinal section; and 
         FIG. 2  is an enlarged view of the upper portion of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The compressed CO 2  gas source is constructed as an insert, which fits in the bunghole of a vessel, extends into the vessel and tightly closes the bunghole. The compressed CO 2  gas source can take the place of the bunghole closure with pressure-equalizing valve according to WO 99/23008 A1. 
     The vessel is filled under pressure with CO 2 -containing liquid through the bunghole usually disposed at the middle of its top end plate. Thereafter the bunghole is tightly closed with the insert. To withdraw the liquid, there can be used an integrated outlet tap, which is disposed on the side wall of the vessel at the height of the bottom end plate thereof. The liquid flows out under the action of internal pressure and gravity, until a reduced pressure is reached in the top space of the vessel above the liquid surface therein. To adjust this correctly and maintain it in controlled manner, the compressed CO 2  gas source is activated. The compressed CO 2  gas source injects CO 2  into the top space of the vessel under a pressure that corresponds to the partial pressure of the CO 2  dissolved in the liquid or that slightly exceeds this partial pressure. Thereby steady emptying of the vessel is ensured. No air is admitted into the top space of the vessel. The CO 2  content of the liquid remains constant. 
     The insert has slender elongated shape, and for the most part is radially symmetric relative to a central axis. It is made largely of plastic. The plastic materials used for its manufacture have proved effective for years for bunghole closures and outlet taps of relevant vessels. The two-component plastic injection-molding technique can be used for manufacture. 
     When the insert is in installed condition, closing the bunghole of the vessel, it projects with a housing  10  into the vessel. At its inside end housing  10  has a chamber  12  for receiving a high-pressure CO 2  cartridge  14  in a snug fit. The head of cartridge  14 , at the end face of which it can be pierced, is proximal to the bunghole. Cartridge  14  has its smallest diameter at a straight cylindrical neck. Here it is sealed with a circumferential seal against the wall of housing  10 . 
     The inside end of chamber  12  is closed with a cover  18 , which is welded or bolted to the wall of housing  10 . 
     Housing  10  is supported externally with a circumferential collar  20  on the beaded rim of the bunghole. On collar  20  there is formed a seal  22 , with which the insert seals the bunghole. 
     A rotary knob  24  countersunk in housing  10  protrudes outwardly beyond collar  20 , and can be actuated to pierce CO 2  cartridge  14 . Rotary knob  24  has a steep male thread  26 , with which it is screwed into a complementary female thread of housing  10 . 
     To pierce CO 2  cartridge  14  there is used a piercing needle  34 , which is structurally combined with the valve member of a pressure-regulating valve  68 . The valve member is mounted together with an elastic diaphragm  36  at the center of the axis of housing  10 . The tip of piercing needle  34  is disposed only a short distance from the end face of CO 2  cartridge  14 . 
     During axial positioning movement of piercing needle  34  on CO 2  cartridge  14 , the valve member lifts from a valve seat  38  of the pressure-regulating valve  68 . The valve seat is made from elastic sealing material and molded onto housing  10 . 
     Piercing needle  34  is urged by a slide  40 , which is disposed between rotary knob  24  and piercing needle  34 . Slide  40  is guided in longitudinal sliding relationship in housing  10 . It is in flush contact with piercing needle  34 , such that end face is against end face. Piercing needle  34  is guided with a central centering extension  42  in a close-fitting opening of slide  40 . 
     Rotary knob  24  and slide  40  are in contact with ridges  46  extending in circumferential direction. There are provided two ridges  46 , which are disposed opposite one another and which each have a circumferential length of approximately 90°. Between ridges  46  there are disposed gaps, into which ridges  46  of the respective other part fit in the manner of a rectangular toothing. Upon actuation, rotary knob  24  is screwed forward against slide  40 , which is axially adjusted in the process. 
     A helical compression spring  48  is clamped between rotary knob  24  and slide  40 . Helical compression spring  48  is disposed around a central, plug-like extension  50  on the outside of slide  40  distal from piercing needle  34  and around a central, axial tappet  52  on the inside of rotary knob  24 . Helical compression spring  48  braces slide  40  against piercing needle  34 . 
     As seen in  FIG. 2 , diaphragm  36  bounds a working space  60  downstream from valve seat  38  of the pressure-regulating valve. The working space  60  has a lateral outlet opening  62 , in front of which there is disposed an elastic O-ring  58 . O-Ring  58  has the function of a non-return valve. It prevents liquid from entering the insert. 
     To pierce CO 2  cartridge  14 , rotary knob  24  is turned by approximately 90°. Slide  40  is moved axially inward by the screwing thrust of rotary knob  24 . Piercing needle  34  is driven axially inward under elastic deformation of diaphragm  36 . The valve member lifts from the valve seat  38 . After piercing, a very small valve space upstream from the head of CO 2  cartridge  14  fills with CO 2  under high pressure. 
     After rotary knob  24  has turned a complete 90° or more, slide  40  springs axially back outward under the force of helical compression spring  48 . For this purpose it is actuated by piercing needle  34 , which is retracted axially by the elastic return deformation of diaphragm  36 . Helical compression spring  48  is compressed. The pressure-regulating valve is closed and a small amount of CO 2  under high pressure is admitted into the working space  60 . The compressive forces of the CO 2  on diaphragm, (36) contribute to the spring-back of slide  40  actuated by the piercing needle. Slide  40  snaps with its ridges  46  into the complementary gaps of rotary knob  24 , and it blocks rotary knob  24  against further actuation. 
     Further opening and closing of the pressure-regulating valve is determined by an equilibrium of forces across diaphragm  36 , established by the elastic properties of diaphragm  36 , the spring constant of helical compression spring  48  and the CO 2  pressure in the working space. The determining factor for the pressure of the discharged CO 2  is the spring constant of helical compression spring  48 . 
     Usually the user will activate the compressed CO 2  gas source when the internal pressure in the vessel has dropped so much that the stream of liquid emerging through the outlet tap is too weak. However, the compressed CO 2  gas source can already be activated beforehand without difficulty even if the internal pressure in the vessel is still high. Introduction of CO 2  into the top space of the vessel does not take place as long as the high internal pressure is acting on O-ring  58  in front of the outlet opening. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  Housing 
           12  Chamber 
           14  High-pressure CO 2  cartridge 
           18  Cover 
           20  Collar 
           22  Seal 
           24  Rotary knob 
           26  Male thread 
           34  Piercing needle 
           36  Diaphragm 
           38  Valve seat 
           40  Slide 
           42  Centering extension 
           46  Ridge 
           48  Helical compression spring 
           50  Extension 
           52  Tappet 
           58  O-ring 
           60  Working Space 
           62  Lateral outlet opening 
           68  Pressure regulating valve