Abstract:
A method of dispensing carbonated beverage comprises the step of providing a beverage dispensing system ( 12 ) comprises a pressure chamber ( 24 ), which chamber accommodates a collapsible beverage container ( 48 ) made of a flexible material. The collapsible beverage container includes a beverage space, a head space, a dispensing device ( 76 ), a tapping line ( 18 ), and an interruption valve ( 40 ). The method further comprises the step of maintaining a first elevated pressure within the pressure chamber ( 24 ), which acts on the collapsible beverage container ( 48 ) for crumpling the collapsible beverage container ( 48 ) at a container crumpling pressure and establishing a second elevated pressure, the first elevated pressure being equal to the sum of the second elevated pressure and the container crumpling pressure. The method still further comprises the step of operating the dispensing device ( 76 ) from the non-beverage dispensing position to the beverage dispensing position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a national phase filing, under 35 U.S.C. §371(c), of International Application No. PCT/EP2013/051576, filed on Jan. 28, 2013, the disclosure of which is hereby incorporated by reference in its entirety. 
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     The present invention relates to a method of dispensing carbonated beverage, a collapsible beverage container and a beverage dispensing system. 
     BACKGROUND 
     Beverage dispensing systems are typically used in beverage dispensing establishments for efficiently dispensing large quantities of beverage. Typically, beverage dispensing systems are used to dispense carbonated alcoholic beverages such as draught beer and cider. However, also non-alcoholic carbonated beverages such as soft drinks may be dispensed using a beverage dispensing system. Beverage dispensing systems are mostly for professional users such as in establishments like bars, restaurants and hotels, however, increasingly also for private users such as in private homes. 
     Professional beverage dispensing systems typically dispense beverage provided in large beverage containers. Such beverage containers may hold 20-50 liters of beverage for a professional beverage dispensing system for allowing typically 50-100 beverage dispensing operations before needing to exchange the beverage container. Conventional beverage containers are made of solid materials such as steel and re-filled a number of times. Recently, beverage containers have been made collapsible and for single use only due to hygiene concerns when refilling solid beverage containers. An example of a beverage dispensing system using collapsible beverage containers is the DraughtMaster™ system provided by the applicant company. Such beverage dispensing systems using collapsible beverage containers typically have the beverage container installed in a pressure chamber. Some examples of prior art beverage dispensing systems follow below: 
     In WO 2007/019848, a beverage dispensing system is described. The beverage dispensing system comprises a pressure chamber, which is adapted to accommodate a beverage container of collapsible material. 
     In WO 2009/024147, a module for a modular beverage distribution system is disclosed. Each system comprises a frame, a pressure chamber and connectors for receiving pressure fluid and for supplying the pressure fluid to the pressure chamber and to the neighbouring module. The system has a separate rinsing line. By using a specially designed discharge valve, alternatively rinsing fluid or beverage may enter the tapping line. Rinsing fluid is provided from a separate pressurized reservoir. The discharge valve includes safety features for avoiding mixing rinsing fluid and beverage. 
     In WO 2010/029122, a method of cleaning the tapping line of a beverage dispensing system is disclosed in which a cleaning and flushing cartridge for internal use is described. The cleaning and flushing cartridge is installed in the pressure chamber similar to a beverage container and dispensed similar to a beverage. 
     WO 2010/060946 and WO 2011/117192 both relate to a method of cleaning the tapping line of a beverage dispensing system in which a cleaning and flushing cartridge for external use is described. The cleaning and flushing cartridge is installed outside the pressure chamber and has a pressure fluid source connected. The rinsing and flushing fluid is dispensed similar to a beverage. 
     WO 2010/060949 relates to a beverage dispensing system having a first and a second detector for generating a control pressure. The method comprises evaluating the control pressures from the control pressure outputs of detectors for determining the operational mode of the beverage dispensing system. 
     In WO 2010/020644, a method of installing a collapsible beverage container in a beverage distribution unit is disclosed. The method comprises the steps of positioning the collapsible beverage container in a sloped position, pivoting the collapsible beverage container in a rotational motion around a support surface and sliding the collapsible beverage container on the support surface. 
     When using long dispensing lines, a significant amount of beverage will remain in the tapping line when the beverage container is empty. In order to avoid that this beverage flows backwards through the tapping line, it is contemplated that a non-return valve may be used in the tapping line. Further, in order to prevent dripping, a spring loaded valve may be used. An example of a beverage dispenser including a plurality of valves is DE 296 04 703 U1, in which an electrical liquor dispensing system is disclosed. The tapping line has a non-return valve and a spring loaded lid. The liquor is propelled from a container through the tapping line by an electrical pump and explicitly not by pressurized gas. 
     When dispensing beverage from the beverage dispensing system using a collapsible beverage container, a pressure fluid, typically a gas, is allowed to enter the pressure chamber. During the dispensing of beverage from the pressure chamber, the pressure fluid acts on the collapsible beverage container and forces the beverage out of the pressure chamber while simultaneously crumpling the collapsible beverage container. The volume of the crumpled collapsible beverage container is thereby reduced corresponding to the amount of the dispensed beverage. The collapsible beverage container is made of flexible and preferably disposable materials such as thermoplastic materials. 
     The interior of the collapsible beverage container is divided into a beverage space constituting carbonated beverage and initially occupying the majority of the interior of the beverage container and a head space filled with gas, primarily constituting CO 2  gas. 
     While performing a dispensing operation, the force applied to the beverage container by the pressure in the pressure chamber causes the beverage to flow out of the beverage container and into a tapping line. The tapping line leads to a dispensing device which may be located at a distant location such as one floor above the pressure chamber. The dispensing device typically has a tapping valve and a tapping handle for allowing an operator to control the tapping valve and thereby the beverage dispensing operation. The operator, such as a bartender or barmaid, uses the tapping device to control the rate of beverage dispensing. 
     A problem often observed when the beverage space of the beverage container is empty or almost empty is that the gas of the head space starts entering the tapping line. Such gas will result in gas bubble formation in the tapping line. The presence of gas bubbles in the tapping line will cause excessive frothing and aeration of the carbonated beverage at the tapping valve of the dispensing device. The carbonated beverage dispensed will thus be very foamy and will have a less than optimal taste and appearance. Typically, this beverage therefore has to be disposed of. This is also an indication for the bar employee to exchange the empty and crumpled collapsible beverage container with a new collapsible beverage container filled with beverage. 
     However, gas will still remain in the tapping line even after the beverage container has been exchanged. This will result in excessive foaming also for the first one or two servings of carbonated beverage. This beverage must be disposed of as well. Thus, the total loss of beverage may amount to 2-4 servings for each beverage container, i.e 1-2 at the beginning of each container and 1-2 at the end of each container, resulting in a loss of about 10% of the beverage included in a typical 20 liter collapsible beverage container. 
     In case a modular beverage dispensing system is used, i.e. a system wherein a single tapping line is fed from a multitude of collapsible beverage containers, the problem is even larger since the beverage spaces of the different collapsible beverage containers may be empty at different times, resulting in even more beverage lost. 
     The object of the present invention is thus to dispense beverage while preventing that any gas from the head space is entering the tapping line. 
     SUMMARY OF THE INVENTION 
     The above object together with numerous other objects, which will be evident from the below detailed description, are according to a first aspect of the present invention obtained by a method of dispensing carbonated beverage, the method comprising the steps of:
         providing a beverage dispensing system, the beverage dispensing system comprising a pressure chamber, the pressure chamber accommodating a collapsible beverage container made of a flexible material, the collapsible beverage container including a beverage space consisting of carbonated beverage and a head space consisting of gas, a dispensing device including a tapping valve and defining a beverage dispensing position and a non-beverage dispensing position, a tapping line interconnecting the collapsible beverage container within the pressure chamber and the dispensing device, and an interruption valve defining an open position and a closed position, the open position allowing carbonated beverage to flow from the beverage space to the dispensing device when the pressure chamber is pressurized, the closed position preventing carbonated beverage to flow from the beverage space to the dispensing device,   maintaining a first elevated pressure within the pressure chamber, the first elevated pressure acting on the collapsible beverage container for crumpling the collapsible beverage container at a container crumpling pressure and establishing a second elevated pressure within the collapsible beverage container, the first elevated pressure being equal to the sum of the second elevated pressure and the container crumpling pressure, the interruption valve assuming the open position when the second elevated pressure exceeds a specific non-zero pressure reference, the interruption valve assuming the closed position when the second elevated pressure falls below the specific non-zero pressure reference, and   operating the dispensing device from the non-beverage dispensing position to the beverage dispensing position for causing the carbonated beverage to be dispensed at the dispensing device and the collapsible beverage container to crumple, provided the interruption valve assuming the open position.       

     The beverage dispensing system may be a non-modular system in which one pressure chamber is connected to one dispensing device via a single tapping line, or a modular system in which a plurality of pressure chambers are selectively connected to one or more dispensing devices via one or more tapping lines. The pressure chamber is typically a pressure proof container connected to a fluid pressure source, typically a high pressure air source. The pressure chamber typically has a pressure lid in order to be able to insert and remove the collapsible beverage container. The collapsible beverage container is typically made of a semi rigid metallic or polymeric material having a thickness such that it is capable of retaining its shape during transport and handling but which may collapse and crumple when subjected to an outer pressure. In most cases a blow molded plastic container will be used. The beverage container may be initially sealed during transport and handling. In a new collapsible beverage container, i.e. a non crumpled container, the beverage space typically occupies about 90% to 95% of the total volume of the beverage container and the head space is occupying the remaining 5%-10%. 
     The tapping line leads from the collapsible beverage container within the pressure chamber to the dispensing device outside the pressure chamber. The dispensing device typically comprise a tapping valve and an tapping handle for the user to be able to selectively dispense or not dispense beverage by switching between the beverage dispensing position in which the tapping valve is open and the non-beverage dispensing position in which the tapping valve is closed. 
     The first elevated pressure to be maintained in the pressure chamber is established after the collapsible beverage container has been installed in the pressure chamber. The first elevated pressure is typically held substantially constant until the collapsible beverage container is to be exchanged at which time the pressure is let out. The first elevated pressure acts uniformly on the wall of the collapsible beverage container in order to establish the second elevated pressure inside the collapsible beverage container. The second elevated pressure is thus the pressure within the beverage. The first elevated pressure is thus transmitted via the wall of the collapsible beverage container to establish the second elevated pressure. In the present context the applicant has surprisingly found out that the second elevated pressure will be smaller than the first elevated pressure and that the difference between the first elevated pressure and the second elevated pressure is constituted by the pressure required to crumple the collapsible beverage container, i.e. the crumpling pressure, for overcoming the internal resistance against a change of the shape of the wall. Further, it has surprisingly found out that the crumpling pressure is dependent on the level of crumpling of the collapsible beverage container, i.e. a new (full) non-crumpled collapsible beverage container will have a much lower resistance against crumpling than an already crumpled beverage container. Thus, the crumpling pressure increases during beverage dispensing as the volume of the beverage space and thereby the total volume of the collapsible beverage container is reduced. The increase in crumpling pressure is non-linear for most materials and most collapsible beverage containers will exhibit an exponential increase in the required crumpling pressure when the beverage space of the beverage container is almost empty. This effect may be explained by the fact that the first few beverage dispensing operations of a new collapsible beverage container will result in an elastic deformation of the wall of the collapsible beverage container. Such elastic deformation is linear in nature. When the beverage space of the collapsible beverage container is almost empty and the collapsible beverage container is significantly crumpled, the deformation of the wall of the collapsible beverage container will exhibit a plastic deformation, which is non-linear and requires a significantly higher crumpling pressure. Thus, the second elevated pressure will be reduced. In the present context it is understood that the crumpling characteristic of a typical collapsible beverage container will be at least somewhat stochastic, i.e. two seemingly identical collapsible beverage containers may crumple slightly differently depending on the internal wall structure of each collapsible beverage container. 
     The above fact may be utilized by employing an interruption valve. The interruption valve is preferably situated in the tapping line adjacent the beverage container. As long as the second elevated pressure is higher than the specific non-zero pressure reference, the interruption valve will be open and allow beverage to pass when the dispensing device assumes the beverage dispensing position. Later, when the collapsible beverage container is almost empty and thus seriously crumpled, the crumpling pressure will have increased, and, provided that the first elevated pressure is held substantially constant, the second elevated pressure will be much smaller. When the second elevated pressure falls below the specific non-zero pressure reference, the interruption valve will be closed and beverage will not be allowed to pass even when the dispensing device assumes the beverage dispensing position. This will allow a very well defined end of the beverage dispensing operations when the collapsible beverage container is empty or nearly empty. 
     The non-zero pressure reference is chosen such that the beverage dispensing is interrupted well before the beverage space is empty such that there is no risk that gas from the head space will enter the tapping line. The specific non-zero pressure reference may thus not be zero, since this would mean that the container crumpling pressure is equal to the first pressure, which first pressure is typically sufficient to completely flatten the collapsible beverage container. In case the first elevated pressure is not significantly higher than the crumpling pressure such that the second elevated pressure is allowed to approach zero, the beverage dispensing will be very slow due to the lack of driving pressure and such situations should also be avoided. Yet further, in case the specific non-zero pressure reference is higher than the first pressure, the interruption valve will always be closed and beverage dispensing never allowed. 
     By choosing a suitable specific non-zero pressure reference, the interruption valve may be closed when the second elevated pressure is still high enough for dispensing and the beverage space still includes a small amount of beverage. In this way, no gas will be introduced into the tapping line. When a new collapsible beverage container is installed, the tapping line will be free from gas and the first servings of carbonated beverage will not suffer from any excessive foaming. The only lost beverage will be the small amount remaining in the crumpled beverage container, however, this amount will be much smaller than the amount of carbonated beverage lost due to excessive foaming. Calculations made by the applicant using a typical 20 liter beverage container have shown that the average loss amounts to a few per mille only, compared to several percent using the prior art beverage dispensing systems. Taking into account the total amount of carbonated beverage dispensed worldwide, a vast amount of carbonated beverage can be saved. 
     According to a further embodiment of the first aspect, the interruption valve is located in the collapsible beverage container, the tapping line or the dispensing device. In one preferred embodiment, the interruption valve is located in the collapsible beverage container. In this way there is no need for any modifications of the permanent parts of the beverage dispensing system. In the case that the interruption valve is located in the beverage container, it is contemplated that it may be used for sealing the beverage container during transport and handling, thereby omitting the need for a separate seal. It is further contemplated that the interruption valve may be provided as a re-usable accessory which is mounted on the collapsible beverage container. In another preferred embodiment, the interruption valve is preferably fixedly mounted in the tapping line adjacent the collapsible beverage container. In this way, ordinary collapsible beverage containers may be used. The pressure in the tapping line may be considered to be equal to the pressure within the collapsible beverage container, at least at a location adjacent the collapsible beverage container. However, in case the tapping line leads to another floor of a building, it is contemplated that the pressure will fall. In yet another preferred embodiment, the interruption valve is located in the dispensing device. In this way, a visual indication may be given that the beverage container is empty. In this embodiment, a non-return valve may be used adjacent the beverage container to avoid a return flow of beverage. Further, the pressure may be slightly lower at the interruption valve than inside the collapsible beverage container depending on the height difference between the collapsible beverage container and the dispensing device. 
     According to a further embodiment of the first aspect, the interruption valve employs a loaded spring or a sealed pressurized gas volume in order to establish the specific non-zero pressure reference. When the second elevated pressure falls below the specific non-zero pressure reference, the interruption valve changes from the open position to the closed position. The specific non-zero pressure reference may be established by a loaded spring having a suitable spring constant and pre-load such that the valve remains open when the second elevated pressure is higher than the specific non-zero pressure reference but closes rapidly when the second elevated pressure falls below the specific non-zero pressure reference. Alternatively, a sealed pressurized gas volume may substitute the spring. 
     According to a further embodiment of the first aspect, the interruption valve is fluidly connected to the first elevated pressure of the pressure chamber via a pressure regulator for establishing the specific non-zero pressure reference. A particular beneficial solution is to make the specific non-zero pressure reference dependent on the first elevated pressure via a pressure regulator acting as a pressure reduction valve. In this way, the non-zero pressure reference may be made dependent on the first elevated pressure, i.e. the pressure in the pressure chamber. In this way, the first elevated pressure may be increased while still allowing the interruption valve to be closed when the collapsible beverage container has been crumpled to such extent that only a very small amount of beverage remains. 
     According to a further embodiment of the first aspect, the interruption valve includes a pressure probe for determining the second elevated pressure and an electromagnetic valve for assuming the open and closed positions, respectively, dependent on the second elevated pressure. The pressure probe may be mounted in the tapping line in order to constantly monitor the second elevated pressure. As soon as the second elevated pressure falls below the specific non-zero pressure reference, an electrical signal may be sent to the electromagnetic valve in order for the interruption valve to close. It is contemplated that a control unit may be used to compensate the specific non-zero pressure reference in order to take account of any changes in the first elevated pressure. 
     According to a further embodiment of the first aspect, the first elevated pressure is in the range of 2-5 bar above atmospheric pressure, preferably 3-4 bar above atmospheric pressure. Such pressures are suitable for achieving a good driving pressure for the beverage which will overcome the crumpling pressure of the collapsible beverage and still allow beverage to be dispensed at a reasonable velocity at a higher location than the location of the beverage container. 
     According to a further embodiment of the first aspect, the second elevated pressure is in the range of 1-4 bar above atmospheric pressure, preferably 2-3 bar above atmospheric pressure. By considering the crumpling pressure, the second elevated pressure must still allow beverage to be dispensed at a reasonable velocity at a higher location than the location of the beverage container. 
     According to a further embodiment of the first aspect, the beverage container is positioned in an upside down orientation within the pressure space such that the beverage space is located adjacent the tapping line and the head space is located spaced apart from the tapping line. With upside down position is meant a position in which the outlet of the beverage container is directed downwardly. In this way, the beverage space will be located adjacent the outlet and the head space will be located as far as possible from the outlet and consequently the head space will not reach the outlet until the beverage space is depleted. This will also completely avoid the use of a ascension pipe. 
     According to a further embodiment of the first aspect, specific non-zero pressure reference is in the range of 0.1-3 bar, preferably 0.5-1 bar, absolute pressure. For most cases such pressure values will be suitable in order to achieve a well defined end of beverage dispensing when the collapsible beverage container is empty or almost empty. 
     According to a further embodiment of the first aspect, the crumpling pressure being dependent on the level of crumpling of the collapsible beverage container, the crumpling pressure being in the range of 0-1 bar absolute pressure when the beverage container is in an initial non-crumpled state whereas the crumpling pressure is in the range of 2-5 bar when the beverage container is in a crumpled state in which the volume of the beverage container is reduced to 5% of the volume of the beverage container in the initial non-crumpled state. As already stated above, the crumpling pressure is dependent on the level of crumpling, i.e. the more crumpled the beverage container is, the higher pressure is required in order to further crumple the beverage container. Initially, the crumple pressure will be very low, or even zero, since the deformation will be elastic and thereby have a linear relationship with the applied force. However, when only 5% of the original volume remains, the applied force is very high and additional deformation will require even higher force since the deformation may be permanent, i.e. a plastic deformation. The crumpling pressure thus typically is exponentially dependent on the dispensed volume of beverage. Thus, the collapsible beverage container is typically made using such material, volume and wall thickness such that when only 5% of the volume remains, i.e. the crumpling pressure is in the range of 2-5 bar. 
     According to a further embodiment of the first aspect, when the interruption valve assumes the closed position, the beverage space has a volume of between 1 and 100 ml, preferably between 10 and 50 ml, such as 40 ml. In order to avoid gas entering the tapping line, at least a tiny amount of beverage should remain in the beverage container when the interruption valve assumes the closed position. However, too much beverage remaining in the beverage container would constitute a waste since such beverage will not be dispensed. Thus, in order to have a safety margin in order to take into account the stochastic differences in the crumpling behavior of different collapsible beverage containers, it is preferred to allow about 40 ml of beverage to remain in the beverage container when the interruption valve assumes the closed position 
     According to a further embodiment of the first aspect, the collapsible beverage container is made of the flexible material constituting a thermoplastic material such as PET. PET is a suitable material since it is sufficiently flexible to be crumpled, it is suitable for food and beverage and it may be disposed of in an environmentally friendly way, e.g. by combustion or recycling. 
     The above object together with numerous other objects, which will be evident from the below detailed description, are according to a second aspect of the present invention obtained by a collapsible beverage container for use together with a beverage dispensing system, the beverage dispensing system comprising a pressure chamber for accommodating the collapsible beverage container, the pressure chamber being capable of maintaining a first elevated pressure within the pressure chamber, the collapsible beverage container being made of a flexible material and including a beverage space consisting of carbonated beverage and a head space consisting of gas, the first elevated pressure acting on the collapsible beverage container for crumpling the collapsible beverage container at a container crumpling pressure and establishing a second elevated pressure within the collapsible beverage container, the first elevated pressure being equal to the sum of the second elevated pressure and the container crumpling pressure, the collapsible beverage container including an interruption valve defining an open position and a closed position, the open position allowing carbonated beverage to flow out from beverage space when the pressure chamber is pressurized, the closed position preventing carbonated beverage to flow out from the beverage space, the interruption valve assuming the open position when the second elevated pressure exceeds a specific non-zero pressure reference, the interruption valve assuming the closed position when the second elevated pressure falls below the specific non-zero pressure reference. 
     The collapsible beverage container according to the second aspect includes the interruption valve. It is contemplated that the collapsible beverage container according to the second aspect, which includes the interruption valve, may be used together with any of the methods described above in connection with the first aspect. 
     The above object together with numerous other objects, which will be evident from the below detailed description, are according to a third aspect of the present invention obtained by a beverage dispensing system comprising:
         a pressure chamber for accommodating a collapsible beverage container made of a flexible material, the collapsible beverage container including a beverage space consisting of carbonated beverage and a head space consisting of gas, the pressure chamber being capable of maintaining a first elevated pressure within the pressure chamber, the first elevated pressure acting on the collapsible beverage container for crumpling the collapsible beverage container at a container crumpling pressure and establishing a second elevated pressure within the collapsible beverage container, the first elevated pressure being equal to the sum of the second elevated pressure and the container crumpling pressure,   a dispensing device including a tapping valve and defining a beverage dispensing position and a non-beverage dispensing position, and   a tapping line interconnecting the collapsible beverage container within the pressure chamber and the dispensing device, the tapping line including an interruption valve defining an open position and a closed position, the open position allowing carbonated beverage to flow from the beverage space to the dispensing device when the pressure chamber is pressurized, the closed position preventing carbonated beverage to flow from the beverage space to the dispensing device, the interruption valve assuming the open position when the second elevated pressure exceeds a specific non-zero pressure reference, the interruption valve assuming the closed position when the second elevated pressure falls below the specific non-zero pressure reference.       

     The beverage dispensing system according to the third aspect includes the interruption valve in the tapping line. It is contemplated that the beverage dispensing system according to the third aspect may be used together with any of the methods described above in connection with the first aspect. The beverage dispensing system according to the third aspect constitutes an alternative solution to the collapsible beverage container according to the second aspect. 
     The above object together with numerous other objects, which will be evident from the below detailed description, are according to a fourth aspect of the present invention obtained by a beverage dispensing system comprising:
         a pressure chamber for accommodating a collapsible beverage container made of a flexible material, the collapsible beverage container including a beverage space consisting of carbonated beverage and a head space consisting of gas, the pressure chamber being capable of maintaining a first elevated pressure within the pressure chamber, the first elevated pressure acting on the collapsible beverage container for crumpling the collapsible beverage container at a container crumpling pressure and establishing a second elevated pressure within the collapsible beverage container, the first elevated pressure being equal to the sum of the second elevated pressure and the container crumpling pressure,   a dispensing device including a tapping valve and defining a beverage dispensing position and a non-beverage dispensing position, the dispensing device including an interruption valve defining an open position and a closed position, the open position allowing carbonated beverage to flow from the beverage space to the dispensing device when the pressure chamber is pressurized, the closed position preventing carbonated beverage to flow from the beverage space to the dispensing device, the interruption valve assuming the open position when the second elevated pressure exceeds a specific non-zero pressure reference, the interruption valve assuming the closed position when the second elevated pressure falls below the specific non-zero pressure reference, and   a tapping line interconnecting the collapsible beverage container within the pressure chamber and the dispensing device.       

     The beverage dispensing system according to the fourth aspect includes the interruption valve in the dispensing device. It is contemplated that the beverage dispensing system according to the fourth aspect may be used together with any of the methods described above in connection with the first aspect. The beverage dispensing system according to the fourth aspect constitutes an alternative solution to the collapsible beverage container according to the second aspect and to the beverage dispensing system according to the third aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a modular beverage dispensing system. 
         FIG. 2A  is an elevation view of a beverage dispensing system having an interruption valve in the tapping line. 
         FIG. 2B  is a detailed cross-sectional view of a portion of  FIG. 2A . 
         FIG. 2C  is a detailed cross-sectional view of a portion of  FIG. 2B . 
         FIG. 2D  is an elevation view of another embodiment of a beverage dispensing system having an interruption valve in the tapping line. 
         FIG. 2E  is a detailed cross-sectional view of a portion of  FIG. 2D . 
         FIGS. 3A and 3B  are cross-sectional views of an interruption valve employing a sealed gas volume, in the closed and open positions, respectively. 
         FIGS. 4A and 4B  are cross-sectional views of an interruption valve employing a loaded spring, showing the valve in the closed and open positions, respectively. 
         FIGS. 5A and 5B  are cross-sectional views of an interruption valve employing a pressure probe and an electromagnetic valve, showing the valve in the closed and open positions, respectively. 
         FIGS. 6A and 6B  are cross-sectional views of an interruption valve employing a pressure reduction valve and a fluid connection to the pressure chamber, showing the valve in the closed and open positions, respectively. 
         FIG. 7  is a partial cross-sectional view of a collapsible beverage container having an interruption valve. 
         FIG. 8  is a cross-sectional view of an alternative beverage dispensing system having an interruption valve in the tapping line. 
         FIGS. 9A and 9B  are perspective views of modular beverage dispensing systems having an interruption valve. 
         FIG. 10  is a plot showing the container crumpling pressure as a function of the volume of the dispensed beverage from the collapsible beverage container. 
         FIG. 11  is a plot showing the results of a proof of concept experiment conducted by the applicant. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective view of an embodiment of a modular beverage distribution system  10  for use with a discharge valve as shown in FIGS. 6-7 of the international application WO 2009/024147. The modular beverage distribution system  8 ′ comprises three modules  12   a ,  12   b ,  12   c , each mounted to a bottom wall  14  and a rear wall  16  constituting a frame. The bottom wall  14  rests on a mounting rack  19 . The three modules  28 ′,  30 ′,  32 ′ are mounted in series on the mounting rack  19 . 
     Each of the modules  12   a ,  12   b ,  12   c , is connected to a tapping line  18  and a gas supply line  20 . An optional rinsing line may be available as described in more detail in the above mentioned WO 2009/024147. The tapping line  18  and the gas supply line  20  are mounted near the bottom wall  61 ″ of each module. Each module  12   a ,  12   b ,  12   c  comprises for each of the above mentioned lines  18   20  an inlet constituting a first type connector, an outlet constituting a second type connector and a branch pipe constituting a third type connector. The branch pipe leads to the discharge valve of each module. The outlets of the first module  12   a  are directly connected to the inlets of the second module  12   h  and the outlets of the second module  12   b  are directly connected to the inlets of the third module  12   c.    
     The gas supply line  20  is connected directly to a pressure generator  22 . The gas supply line  20  is further connected to a pressure chamber  24  of the beverage dispensing module  12   a  via a security valve (not shown). The gas supply line  20  is connected to a pressure inlet  26  of the beverage dispensing module  12   b  via a pressure outlet  28 . The fluid path  4 T may also provide driving pressure to the discharge valve which is shown in  FIGS. 2A-C . The pressure outlet  48 ′ of the last beverage dispensing module  12   c  is left without connection but has a check valve to avoid pressure fluid escaping. 
     The tapping line inlet  30  of the beverage dispensing module  12   a  is left without connection, however a check valve is provided to prevent beverage from flowing out. The tapping line inlet  30  of the first module  12   a  is connected to the tapping line  18 , which is connected to a tapping line inlet  30 ′ of the beverage dispensing module  12   b  via the tapping line outlet  32  of the beverage dispensing module  12   a . The tapping line outlet  32 ′ of the beverage dispensing module  12   b  is similarly connected to a tapping line inlet  30 ″ of the beverage dispensing module  12   c . The tapping line outlet  32 ′ of the tapping line  18  of the beverage dispensing module  12   c  is connected via a cooling system  34  to a dispensing device (not shown). The tapping line  18  is connected to a discharge valve of each beverage dispensing module  12   a ,  12   b ,  12   c , as shown in  FIG. 2 . 
       FIG. 2A  shows a beverage dispensing system  12  which may be part of a modular beverage dispensing system as shown in connection with  FIG. 1 , however, it may as well be part of a stand-alone beverage dispensing system. The beverage dispensing system  12  comprises a pressure chamber  24  for accommodating a collapsible beverage container and a pressure lid  36  for allowing access to the pressure chamber  24 . The pressure chamber is connected to a tapping line  18 . The tapping line  18  comprise a discharge valve  38  and an interruption valve  40 . 
       FIG. 2B  shows a close up view of the lower part of the beverage dispensing system  12  including the optional discharge valve  38 . The discharge valve  38  comprises a rod or piston  42 , which is located inside a coupling housing  44  and which is adapted to act on a closure element  46  of the collapsible beverage container  48  included in the pressure chamber. The closure element  46 , which is optional, is in the present embodiment not a part of the coupling housing  44 , but part of the collapsible beverage container  48 . The discharge valve  38  is operable between three possible positions, which constitute a first position, an opposite second position and an intermediate position. As will be described in greater detail below, the intermediate position constitutes the beverage dispensing position, whereas the first and second positions constitute an optional rinsing position and the closed position, respectively. 
     The closure element  46  is located in a specific space in the collapsible beverage container  48  between an inlet constriction and an outlet constriction. The inlet constriction and the outlet constriction both provide openings or apertures for allowing beverage to flow from the collapsible beverage container  48 . Both the inlet constriction and the outlet constriction constitute valve seats, which the closure element  46  may seal against. The closure element  46  will either establish a seal against the inlet constriction or the outlet constriction, or remain in the intermediate position, shown in which constitutes the beverage dispensing position. 
     When the rod or piston  42  is in the beverage dispensing position, i.e. in the active or intermediate position, the closure element  46  is located in the intermediate position between the inlet constriction and the outlet constriction as the bottom end of the closure element  46  is resting on a top surface of the coupling housing sealing gasket  50  which, as is evident from  FIG. 2B , seals against the bottom surface of the collapsible beverage container  48 . In the intermediate position shown in  FIG. 2B , the rod or piston  42  is in a lower position, in which the rod or piston is disengaged from contact with the coupling housing sealing gasket  50  allowing free passage through the coupling housing sealing gasket  50 . Consequently, the beverage may flow from the beverage container  48  past the closure element  46  and through the coupling housing sealing gasket  50 , and the interior of the coupling housing  44 , to the tapping line  18 . 
     When the coupling housing  44 , and thereby also the rod or piston  42 , is separated from the beverage container  48 , the beverage, indicated by the signature of “circles” in the figure, will exert a force on the closure element  46  pushing the closure element  46  against the outlet constriction defining the closed position, i.e. the second passive position, thereby sealing off the beverage container  48 . 
     As shown in  FIG. 7 , the beverage container  48  may be fitted with a base part  47  and a connector component  49 , wherein the top part of the discharge valve  38  is received. The closure element  46 , the inlet constriction and the outlet constriction are components of the beverage container  48 . From the beverage dispensing position shown in  FIG. 2B , the rod or piston  42  may be shifted towards the beverage container  48 , or alternatively towards the tapping line  18 . 
     The pressure chamber may be pressurized only when beverage dispensing is allowed, i.e. when a beverage container  48  has been installed and the pressure chamber has been swung into vertical orientation. Consequently, the pressure inside the pressure chamber may be used for holding the rod or piston  42  in the beverage dispensing position shown in  FIG. 2B . In the following, it is assumed that the closure element  46  is located in the intermediate position, i.e. allowing beverage to pass. 
       FIG. 2C  shows a close-up view of the interruption valve  40 . The interruption valve  40 , which forms part of the tapping line, comprises an inlet section  52  and an outlet section  54 . In-between the inlet section  52  and the outlet section  54 , a valve plate  56  is located. When the interruption valve  40  is in the closed position as shown in  FIG. 2C , the valve plate bears against a valve seat  58 , which forms part of the inlet section  52  in order to completely seal off the inlet section  52 . 
       FIG. 2D  shows two beverage dispensing systems  12  which are interconnected by a common tapping line  18 . Each of the beverage dispensing systems  12  includes an interruption valve  40  and a non-return valve  79  connected downstream in relation to the interruption valve  40 . The purpose of the non-return valve  79  is to avoid beverage flowing back towards the interruption valve  40  when the beverage dispensing is interrupted. 
       FIG. 2E  shows a close up view of the interruption valve  40  and the non-return valve  79 . The non-return valve may constitute a ball valve that is suspended in a weak wire which allows beverage to pass in a direction from the beverage container to the tap and which immediately closes the passage when the beverage starts to flow in the other direction. 
       FIG. 3A  shows an interruption valve  40  employing a sealed gas volume  60 . The interruption valve  40  is in the closed position. The sealed gas volume  60  has a predetermined pressure and communicates with the valve plate  56  via a sealed bellows  62  such that the valve plate  56  applies a specific non-zero pressure force against the valve seat  58 . 
       FIG. 3B  shows an interruption valve  40  employing a sealed gas volume  60 . The interruption valve  40  is in the open position. When the pressure in the inlet section  52 , which is considered to correspond to the pressure in the collapsible beverage container, exceeds the pressure in the sealed gas volume  60 , the valve plate  56  will move away from the valve seat  58  and allow beverage to pass from the inlet section  52  to the outlet section  54 . When the pressure in the inlet section  52  again falls below the pressure in the sealed gas volume  60 , the valve plate  56  will move towards the valve seat  58  and effectively prevent beverage from passing from the inlet section  52  to the outlet section  54 . 
       FIG. 4A  shows an interruption valve  40 ′ employing a spring  63 . The interruption valve  40 ′ is in the closed position. The spring  63  has a predetermined spring constant and pre-load force and is mechanically connected to the valve plate  56  such that the valve plate  56  applies a specific non-zero pressure force against the valve seat  58 . 
       FIG. 4B  shows an interruption valve  40 ′ employing a spring  63 . The interruption valve  40 ′ is in the open position. When the pressure in the inlet section  52 , which is considered to correspond to the pressure in the collapsible beverage container, exhibits a pressure force onto the valve plate  56  which exceeds the pre-load force of the spring  63 , the valve plate  56  will move away from the valve seat  58  and allow beverage to pass from the inlet section  52  to the outlet section  54 . When the pressure in the inlet section  52  again exhibits a pressure force onto the valve plate  56 , which falls below the pre-load force of the spring  63 , the valve plate  56  will move towards the valve seat  58  and effectively prevent beverage from passing from the inlet section  52  to the outlet section  54 . 
       FIG. 5A  shows an interruption valve  40 ″ employing an electromagnetic actuator  64 . The interruption valve  40 ″ is in the closed position. The electromagnetic actuator  64  is mechanically connected to the valve plate  56  and applies a sufficiently high pressure force against the valve seat  58  such that no beverage may pass. A pressure probe  66  is located in the inlet section  52  and measures the pressure of the beverage in the inlet section  56 , which is considered to correspond to the pressure in the collapsible beverage container. The pressure is constantly evaluated by a control unit  68  and compared to the specific non-zero pressure reference. 
       FIG. 5B  shows an interruption valve  40 ″ employing an electromagnetic actuator  64 . The interruption valve  40 ″ is in the open position. When the pressure measured by the pressure probe in the inlet section  52  exceeds the specific non-zero reference value, the control unit  68  will send a signal to the electromagnetic actuator for the valve plate  56  to move away from the valve seat  58  and allow beverage to pass from the inlet section  52  to the outlet section  54 . When the pressure in the inlet section  52 , measured by the pressure probe  66 , again falls below the specific non-zero reference value, the electromagnetic actuator  64  will again make the valve plate  56  move towards the valve seat  58  and effectively prevent beverage from passing from the inlet section  52  to the outlet section  54 . It is contemplated that the control unit may modify the specific non-zero reference value depending on the collapsible beverage container used and on the pressure in the pressure chamber. 
       FIG. 6A  shows an interruption valve  40 ′″ employing a gas volume  70  similar to the embodiment shown in connection with  FIG. 3A . The interruption valve  40 ′″ is in the closed position. The gas volume  70  communicates with the valve plate  56  via a sealed bellows  62 , but distinguishes from the embodiment shown in connection with  FIG. 3A  in that the gas volume  70  is not sealed but connected via a pressure line  72  and a pressure reduction valve  74  to the pressure chamber, such that the valve plate  56  applies a specific non-zero pressure force, which is dependent on the pressure in the pressure chamber, against the valve seat  58 . 
       FIG. 6B  shows an interruption valve  40 ′″ employing a gas volume  70 . The interruption valve  40 ′″ is in the open position. When the pressure in the inlet section  52 , which is considered to correspond to the pressure in the collapsible beverage container, exceeds the pressure in the gas volume  70 , the valve plate  56  will move away from the valve seat  58  and allow beverage to pass from the inlet section  52  to the outlet section  54 . When the pressure in the inlet section  52  again falls below the pressure in the gas volume  70 , the valve plate  56  will move towards the valve seat  58  and effectively prevent beverage from passing from the inlet section  52  to the outlet section  54 . In this way the specific non-zero pressure reference may be modified depending on the pressure in the pressure chamber in order to establish an optimal closing occasion independent of the pressure in the pressure chamber. 
       FIG. 7  shows a collapsible beverage container  48 ′ having an interruption valve  40 ″″ and being mounted on a discharge valve  38  as described in  FIGS. 2A-C . The collapsible beverage container  48 ′ is located within a pressure chamber. The interruption valve  40 ″″ is similar to the valve described in connection with  FIGS. 2C and 3A . The interruption valve  40 ″″, which forms part of the collapsible beverage container  48 ′, comprise a valve plate  56 ′. When the interruption valve  40 ″″ is in the closed position, the valve plate bears against a valve seat  58 ′ in order to completely seal off the collapsible beverage container  48 ′. The sealed gas volume  60 ′ has a predetermined pressure and communicates with the valve plate  56 ′ via a sealed bellows  62 ′ such that the valve plate  56 ′ applies a specific non-zero pressure force against the valve seat  58 . When the pressure in the collapsible beverage container  48 ′ exceeds the pressure in the sealed gas volume  60 ′, the valve plate  56 ′ will move away from the valve seat  58 ′ and allow beverage to pass. When the pressure in the collapsible beverage container  48 ′ again falls below the pressure in the sealed gas volume  60 ′, the valve plate  56 ′ will move towards the valve seat  58 ′ and effectively prevent beverage from passing. 
       FIG. 8  shows an alternative beverage dispensing system  12 ′ having an interruption valve  40  in the tapping line  18  similar to the embodiment shown in connection with  FIGS. 2A and 2B . However, the discharge valve has been omitted such that a straight passage is achieved from the beverage container  48  through the tapping line  18 , except for the provision of the interruption valve  40 . It is understood that the interruption valve  40  may be located in the tapping line  18  as indicated in the figure or alternatively the interruption valve  40  may be located in the beverage container  48  as indicated in  FIG. 7 . 
       FIG. 9A  shows a modular beverage dispensing system  10 ′ including beverage dispensing modules  12  and a dispensing device  76 . The dispensing device includes a bar counter  78  and a number of beverage taps  80 , each including a tapping valve (not shown) and a tapping handle. The beverage dispensing operations are controlled by the tapping handle. The tapping lines  18  lead via a cooling system  34  to the taps  80 . Each tapping line  18  is provided with an interruption valve (not shown), which may be included in the respective tap  80  or located adjacent the tap  80 . The interruption valve may resemble any of the interruption valves shown in  FIGS. 3A-6B . A non-return valve  79  may be installed in the tapping line  18  in order to avoid a return flow of beverage to the pressure chamber when exchanging beverage container. 
       FIG. 9B  shows a modular beverage dispensing system  10 ″ which is similar to the beverage dispensing system of  FIG. 9A  except that the three tapping lines  18  originating from a respective beverage dispensing system  12  converge to a single tapping line which continues to a single tap  80 . Each of the tapping lines  18  has an interruption valve  40 ″″ and a non-return valve  79  located adjacent the beverage dispensing system. 
       FIG. 10  shows a plot of pressure versus volume of the dispensed beverage from the collapsible beverage container. The curve  82  illustrates a constant first elevated pressure corresponding to the pressure in the pressure chamber. The curve  84  (dashed) illustrates the container crumpling pressure of the collapsible beverage container, i.e. the pressure required to crumple the beverage container, as a function of the volume of the dispensed beverage. When no or only very little beverage has been dispensed, the crumpling pressure is substantially constant. When a significant amount of beverage has been dispensed, the crumpling pressure increases exponentially. The curve  86  illustrates the second elevated pressure within the collapsible beverage container as a function of the volume of the dispensed beverage. As the crumpling pressure increases, the second elevated pressure decreases, as the sum of the crumpling pressure  84  and the second elevated pressure  86  is equal to the first elevated pressure  82 . The curve  88  illustrates the specific non-zero pressure reference. When the second elevated pressure  86  falls below the specific non-zero pressure reference  88 , the interruption valve closes and the beverage dispensing is interrupted. 
       FIG. 11  shows a plot of a proof-of concept experiment performed by the applicant. The curve  90  illustrates the pressure in the collapsible beverage container, i.e. the second elevated pressure, as a function of time during a number of dispensing operations using a constant pressure in the pressure chamber, i.e. the first elevated pressure, of 3.5 bar. The beverage dispensing operations are begun at time α 1  when the dispensing device is switched from the non-beverage dispensing position to the beverage dispensing position. The beverage dispensing yields a relative pressure drop of about 1 bar. At time β 1  the dispensing device is switched back from the beverage dispensing position to the non-beverage dispensing position, thereby closing the tapping valve. This results in a shock wave and pressures up to 4.5 bar, however, the pressures quickly sink towards the initial pressure of about 3.5 bar. Further, similar beverage dispensing operations are performed at times α 2 , β 2 , α 3  and β 3 . At time β 3 , the crumpling pressure has increased such that the second elevated pressure no longer reaches the initial pressure of 3.5 bar, but just 2.5 bar. At time α 4 , the dispensing device is again switched from the beverage dispensing position to the non-beverage dispensing position resulting in a constant pressure drop from 2.5 bar to 0.5 bar, at which time the interruption valve closes and beverage dispensing is finally interrupted. 
     LIST OF PARTS WITH REFERENCE TO THE FIGURES 
     
       
         
               
             
           
               
                   
               
             
             
               
                 10. Modular beverage dispensing system 
               
               
                 12. Beverage dispensing system (module) 
               
               
                 14. Bottom wall 
               
               
                 16. Rear wall 
               
               
                 18. Tapping line 
               
               
                 19. Mounting rack 
               
               
                 20. Gas supply line 
               
               
                 22. Pressure generator 
               
               
                 24. Pressure chamber 
               
               
                 26. Pressure inlet 
               
               
                 28. Pressure outlet 
               
               
                 30. Tapping line inlet 
               
               
                 32. Tapping line outlet 
               
               
                 34. Cooling system 
               
               
                 36. Pressure lid 
               
               
                 38. Discharge valve 
               
               
                 40. Interruption valve 
               
               
                 42. Rod 
               
               
                 44. Coupling mechanism 
               
               
                 46. Closure element 
               
               
                 48. Collapsible beverage container 
               
               
                 50. Sealing gasket 
               
               
                 47. Base part 
               
               
                 52. Inlet section 
               
               
                 54. Outlet section 
               
               
                 56. Valve plate 
               
               
                 58. Valve seat 
               
               
                 60. Sealed gas volume 
               
               
                 62. Bellows 
               
               
                 63. Spring 
               
               
                 64. Electromagnetic actuator 
               
               
                 66. Pressure probe 
               
               
                 68. Control unit 
               
               
                 70. Gas volume 
               
               
                 72. Pressure line 
               
               
                 74. Pressure reduction valve 
               
               
                 76. Dispensing device 
               
               
                 78. Bar counter 
               
               
                 79. Non-return valve 
               
               
                 80. Beverage taps 
               
               
                 82. First elevated pressure 
               
               
                 84. Container crumple pressure 
               
               
                 86. Second pressure 
               
               
                 88. Specific non-zero pressure reference  
               
               
                 90. Curve 
               
               
                 49. Connector component