A gas restrictor and a method for restricting gas

Abstract

A gas restrictor (1) for a beverage dispensing system, said gas restrictor device (1) comprising a chamber (2) having gas port (3) and an liquid outlet port (4) wherein said gas port (3) and said liquid outlet port (5) being associated with an electrical or pneumatic controllable shut-off valve (v3, v4) to control a flow of fluid through said gas port (3) and said liquid outlet port (4) individually from each other.

Description

The invention relates to a gas restrictor, preferably, for a beverage dispensing system, said gas restrictor device comprising a chamber having gas port and an liquid outlet port wherein said gas port and said liquid outlet port being associated with an electrical or pneumatic controllable shut-off valve to control a flow of fluid through said gas port and said liquid outlet port individually from each other. BACKGROUND OF THE INVENTION In many beer dispensing system beer is pressurized contained in a keg. The pressure forces the beer to an outlet of a beer tap, when the beer tap is opened for dispensing of beer. When the keg is nearly empty, opening of the beer tap result in that the residue of beer foams-up and foam fills the whole beer line from a keg coupler to the beer tap. After fitting a new keg to the beer line, one is faced with the problem of getting rid of the foam which quite often is a cumbersome process which involves purging the beer line with larger quantities of beer from the new keg. This clearly being disadvantages. In other dispensing systems, such as systems for dispensing e.g. cider contained in a pressurized keg, foam may not necessarily be formed when the keg is nearly empty. However, gas will flow out of the keg toward a tap for dispensing the cider, which generally is undesirable as the gas then needs to purged out similarly to purging of beer foam. Accordingly, foam and gas shares the same disadvantages as foam may be considered as a gas containing substance. Hence, an improved gas handling would be advantageous, and in particular a more efficient and / or reliable foam handling would be advantageous. OBJECT OF THE INVENTION In particular, it may be seen as an object of the present invention to provide a device and method that solves the above mentioned problems of the prior art with purging. It is a further object of the present invention to provide an alternative to the prior art. SUMMARY OF THE INVENTION Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a gas restrictor for a beverage dispensing system, said gas restrictor device comprising: • a chamber 2 having: o gas port and an liquid outlet port wherein said gas port and said liquid outlet port being associated with an electrical or pneumatic controllable shut-off valve to control a flow of fluid through said gas port and said liquid outlet port individually from each other; o a liquid inlet port; wherein o said gas port is situated at position being vertically higher than a vertical position of said liquid outlet port, • a level sensor configured to detect that a surface of a liquid contained within said chamber is positioned at a predefined level, preferably being at said gas port, and provide provide an electrical position signal representing that said liquid surface is at predefined level; • an electronic controller being o electrical connected with an actuator of each of said associated valves, said actuators being configured to open and close each of said valves individually by said controller providing an electrical control signal to said actuators, o electrical connected with said level sensor to receive said electrical position signal; • said electronic controller being configured to set said associated valves in one or more of the three configurations: o a gas detected configuration in which said associated valves both are closed, said gas detected configuration is set by the controller when said liquid surface is below said gas port; o a gas purge configuration in which said valve associated with said gas port is open and said valve associated with said liquid outlet port is closed, said gas purge configuration being set by the controller receiving a purge instruction, and o a liquid dispensing configuration in which said valve associated with said liquid outlet port is open and said valve associated with said gas port is closed, said liquid dispensing configuration is set by the controller when said liquid surface is at said predefined level. "Beverage" as used herein preferably refers to a drinkable liquid being pressurized in a container, such as a keg, and to be dispensed via a beverage dispensing system. Examples on beverage includes, but not limited to, are beer, cider, wine, juice, must, soft drink, fizzy drink and water. "Gas" as used herein preferably refers to a fluid being in a gas phase, or to foam in which the gas is contained in bubbles. It is noted that a combination of gas and foam is, preferably, also considered to be a gas. "At a position being higher" is used to reference a position where higher is evaluated relatively to gravity during use. In the figures, the direction of gravity is indicated by an arrow labelled "g". "Surface of a liquid" and "liquid surface" are used interchangeably herein. "Gas restriction" as used in connection with a "gas restrictor" is used to reference that gas is restricted, such as prevented, from flowing into a fluid line connecting the gas restrictor with a beverage tap. "Gas collector" as used herein may refer a container, a bucket or another suitable device for collecting the purged gas. In embodiments, where the purges gas can be released to a surrounding atmosphere, such as when the gas is smaller amounts of CO2 the gas collector may be a space, such as a room, in which the gas restrictor is arranged during use. In a second aspect the invention relates to A system comprising a gas restrictor according to the first aspect, and a rail in which an flow channel is formed having an opening facing towards the gas restrictor and wherein the gas restrictor is attached to a rail in a position where a channel being in fluidic connection with said gas port via said valve associated with said gas port, when said valve is open, so as to allow gas being purged from said chamber to flow into said channel. In a third aspect the invention relates to a method of restricting gas from flowing to a beverage tap in a beverage dispensing system comprising a gas restrictor according to first aspect, wherein • said liquid inlet port is fluidicly via said valve associated with the liquid inlet port to a keg to receive beverage from said keg; • said liquid outlet port is fluidicly connected via said valve associated with said liquid outlet port to a beverage tap to receive beverage flowing into said chamber through said inlet port and out from said chamber though said liquid outlet port, said method comprises • said controller closes said valve associated with said liquid outlet port, when said level sensor do not detect said liquid surface at said gas port; • said controller sets said associated valves in said gas purge configuration upon receipt of a purge instruction; • said controller sets said associated valves in said liquid dispensing configuration when said level sensor detects said liquid surface at said gas port. BRIEF DESCRIPTION OF THE FIGURES The present invention and in particular preferred embodiments thereof will now be described in more detail with regard to the accompanying figures. The figures show ways of implementing the present invention with reference to a beer dispensing system, and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. Fig. 1 schematically illustrates in a cross sectional view a first embodiment of a gas restrictor. Fig. 2 schematically illustrates in a cross sectional view a second embodiment of a gas restrictor. Figs. 3A-G illustrate in a semi-transparent views of a third embodiment of gas restrictor. Figs. 3B-F are close-ups of the restrictor in Fig. 3A although shown in various configurations. In Figs. 3A and 3B, a gas purge configuration is illustrated; Figs. 3C, 3D and 3E illustrate different positions of the associated valves. In Figs. 3F, shown in gas purge configuration, although valve V4 being closed is not visible due to presented view, the channel for gas purge is shown in combination with valve V3 being open and in Fig. 3G a beer dispensing configuration is disclosed in a cross sectional view with valve V4 open. Fig. 4 schematically illustrates in a cross sectional view a fourth embodiment of a gas restrictor. Fig. 5 schematically illustrates in a cross sectional view a sixth embodiment of a gas restrictor. Fig. 6 illustrates in a 3-dimensional view, the gas restrictor of Figs. 3A-G being attached to a rail. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In the following, preferred embodiments of the invention will be described with reference to a beer dispensing system, where the beverage to be dispensed is beer and the gas to be restricted is foam. Reference is made to in particular Figs. 1 and 2 illustrating respectively a preferred embodiment of gas restrictor for a beer dispensing system. As illustrated, the gas restrictor device has a chamber 2 being a void formed inside a cylindrical wall 17 being closed at an upper and at a lower end. The wall may have other forms than cylindrical. The chamber has gas port 3 and an liquid outlet port 4. Here port refers to an opening through which a fluid, such as foam or beer may flow into or out from the chamber. The gas port 3 and the liquid outlet port 4 are each associated with an electrical or pneumatic controllable shut-off valve V3, V4 to control a flow of fluid through the gas port 3 and said liquid outlet port 4 individually from each other. In the illustrated embodiments the valves V3, V4 are arranged downstream of the ports, where downstream refers to direction of fluid during use. The chamber also has a liquid inlet port 5 which is used to introduce a fluid, such as beer or a cleaning agent into the chamber 2. The gas port 3 is situated at position being vertically higher than a vertical position of said liquid outlet port 4. The liquid outlet port is preferably arranged at a lower end of the chamber 2, such as at the bottom of the chamber 2 as illustrated in e.g. Fig. 1. In order to detect the level of a liquid inside the chamber 2, a level sensor 6 configured to detect that a surface of a liquid (beer) contained within the chamber 2. Preferably, the level sensor is configured detect the position of the liquid surface 14 inside the chamber e.g. relatively to the gas port, such as being positioned at said gas port 3, and provide provide an electrical position signal representing the position of the liquid surface, such an electrical position signal representing that liquid surface is at the gas port 3 as illustrated in Figs. 1 and 2. The device comprises and an electronic controller 7 being capable of controlling actuators of the valves V3, V4 to open or close the valves. Accordingly, the electronic controller 7 is electrical connected with an actuator 16 of each of the associated valves V3, V4, where the actuators being configured to open and close each of said valves V3, V4 individually by the controller 7 providing an electrical control signal to the actuators. The electronic controller 7 is electrical connected with the level sensor 6 to receive the electrical position signal from the level sensor 6. The electronic controller 7 is configured to set the associated valves V3, V4 in three configurations: • a gas detected configuration in which said associated valves V3 and V4 both are closed, said gas detected configuration is set by the controller (7) when said liquid surface is, such as falls, below the preselected level, such as below the gas port (3); • a gas purge configuration in which the valve V3 associated with the gas port 3 is open and the valve V4 associated with the liquid outlet port 4 is closed. The gas purge configuration is used to purge out foam collected inside the chamber 2 by an inflow of liquid (beer). As the foam has lower density than the inflow of liquid, and the liquid outlet port is closed, the foam "rest" on top of the liquid surfaces and is forced out of the chamber 2 through the gas port 3. The gas purge configuration is set by the controller receiving a purge instruction. Such a purge instruction is typically provided by a manual input, e.g. by an operator pushing a button which input is converted into a purge instruction for the controller 7. The purge of foam is, preferably ended, when the liquid level has raised to the predefined level (detected by the level sensor), such as at the level of the foam port 3, which result in that the controller closes valve V3 as disclosed here below. • a liquid dispensing configuration in which said valve V4 associated with the liquid outlet port 4 is open and the valve associated with the gas port 3 is closed. In this configuration, liquid (beer) flowing into the chamber 2 through port 5 will flow towards liquid outlet port 4 and out of the chamber 2 through this port 4. The liquid dispensing configuration is typically a configuration following the gas purge configuration and is set automatically by the controller when the level detector 5 signals during purging that the liquid surface is a certain position, such as at preselected level, such as at the gas port 3. The preselected level is typically set by an operator (human being) typically so that the liquid level can rise to at least a level of the gas port 3. This typically means that the operator decides the level and installs and / or configures the level sensor accordingly. Different types of level sensor can be used. In some embodiments, the level sensor is configured to detect that the level is at or above / below the pre-selected level only, and in other embodiments the level sensor is configured to detect the level substantial continuously. In the first case, the signal from the level sensor may be a Boolean-like signal. In the latter case, the signal from the sensor may be an ohmic resistance proportional to the position of the float. In both cases, the sensor is typically based on that the float is magnetic which is arranged on a sensing rod, forming the pick-up device, configured to provide a readout based on the position of the float. That the liquid surface is at the gas port 3 typically refers to the position of liquid surface, when liquid will flow into the gas port 3. As illustrated in particular in Figs. 1 and 2, a gas restrictor is in preferred embodiment fluidicly connected to a keg containing beer 13. The beer in the keg 13 is pressurized and flow through the gas restrictor to a beer tap when the gas restrictor is in liquid dispensing configuration. When the keg begins to become empty, foam will be formed inside the chamber 2. Formation of foam will be detected by the level sensor 6 as the foam will "rest" (as will a gas in general) on top of the liquid surface and the liquid surface will drop to a position below the gas port 3. Often, the formation of foam occurs so rapidly that essentially chamber will be filled by foam. It is noted, that formation of foam occurs while the beer tap is open for dispensing beer, that is a flow connection is present between the keg, through the gas restrictor and to the beer tap. When the level detector detects that the liquid surface has dropped e.g. below the gas port 3, this signal is received by the controller which automatically sets the associated valves V3, V4 in shut-off configuration, in which the associated valves V3, V4 both a closed. Now, an operator can change the keg with a keg containing beer. After change of the keg, the operator provides the purge instruction whereby the controller opens the valve v3 associated with the gas port 3 while assuring the valve V4 associated with the liquid outlet 4 port is closed. This will accomplish a flow of beer in liquid form into the chamber and as the foam rest on top of the liquid (as will a gas in general), the foam will be pushed out of the chamber 2 through the gas port 3, until the level detector detects a liquid surface at the level of the gas port 3. When this occurs, the controller receives from the level detector the position signal and sets the associated valves V3, V4 in the liquid dispensing configuration. Beer can now be dispensed from the beer tap and essentially no gas has entered into the fluid line between the gas restrictor and the beer tap. As indicated in the Figs. 1 and 2, the foam is preferably led to a gas collector, which may be a container, a bucket or another suitable device for collecting the purged foam, or even a surrounding atmosphere. As illustrated in Fig. 1, the gas restrictor may have a gas pipe 8 extending upwardly inside said chamber 2, and this gas pipe 8 forms the gas port 3 at an upper end of the gas pipe 8. The gas pipe extends to the bottom of the chamber and is has a connection leading to the exterior of the chamber 2, thereby forming a flow passage from the gas port 3 towards the valve V3 associated with said gas port 3. As an alternative to use of a gas pipe, the gas port 3 may be provided in the wall 17, typically at an upper end of the chamber. This is illustrated in Fig. 2, where an opening in the wall 17 is provided forming the gas port 3. Fig. 1 illustrates that a gas restrictor may have an inlet pipe 12 extending upwardly inside the chamber 2, where the inlet pipe 12 forms the inlet port 5 at an upper end of the inlet pipe 12 and forms a flow passage into the chamber 2. The lower end of the inlet pipe 12 is fluidicly connected with the associated valve V3. In the embodiment of Fig. 1 the liquid outlet port 4 is arranged in a vertically lower position than a position of the inlet port 5. As illustrated, the liquid inlet port 5 may be situated at elevated position relatively to the vertical position of the liquid outlet port 4, which at least some extends inhibits the incoming liquid to flow directly into the liquid outlet port 5, whereby the possibility of creating dead region(s) inside the chamber is at least to some degree is prevented. A dead region(s) refers to a regions where the same fluid remains unaffected of incoming fluid. In preferred embodiments, the level sensor 6 being arranged an inside and at an upper end of said chamber 2 and a float 9 being moveable between at least an upper and a lower position. Such a level sensor 6 is e.g. disclosed in Figs. 1, 2 and 5. In Figs. 1 and 2 the float is disclosed in the upper position and in Fig. 5 the float is disclosed in the lower position. The lower position may alternatively be at the lower end of the chamber. The level detector has a pick-up device being configured to provide an electrical position signal representing that the float 9 is in said upper position. As detailed above, the float is preferably magnetic and the pick-up device may be device configured to sense the magnetism of the float. The level sensor may an ordinary level sensor based on ohmic resistance measurement and / or magnetic responses. While the level sensor in the figures is illustrated as comprising a float moving vertically up and down, the float may also be arranged on a pivoting arm. The level sensor may also be an ultrasound based level sensor. While the level detector may be configured to determine the position of the float in essentially any positions between the upper and lower position, is the preferred that the level sensor is configured provide a signal when the float is in the upper position. Preferably, the upper position is a position of the float 9 provided by the liquid surface being at the predefined level, typically at the gas port (3), and the lower position is preferably a position of the float 9 provided by the liquid surface being below predefined level, typically at the gas port 3. In applications involving beer, the float typically has a density smaller than a density of water, and larger than 5%, such as larger than 10%, preferably larger than 15% of the density of water. This is based on that the density of beer is substantially equal to the density of water, whereas the density of foam formed by beer is typically less the 15%, such as less than 10%, such as less than 5% of the density of beer (water). By this, is may be assured that the float will float in liquid beer and not float in beer foam. To allow for an effective purging of foam out of the chamber 2 through the gas port, the volume of the chamber above the gas port 3 should preferably be small. The volume above the gas port 3 is typically evaluated as the volume defined as the volume above a virtual division of the chamber 2 by a virtual flat surface passing through the gas port 3. In preferred embodiments, the volume of the chamber 2 above the gas port 3 is smaller than 10%, such as smaller than 5%, preferably smaller than 2% of a total volume of the chamber (2). The volumes here considered is preferably evaluated as the void without e.g. the float 9 and / or other elements. It is generally preferred to avoid formation of larger quantities of gas and at the same allow for sufficient time for the associated valves to be set into the gas detected configuration. As it takes some time for the level sensor to detect gas, the volume of the chamber could preferable be larger than the amount of beer that flows out from the chamber before gas is detected and the valve V4. In preferred embodiments, a total interior volume of said chamber (2) is, preferably, between 80 cm3 and 200 cm3, such as between 100 cm3 and 150 cm3. Reference is now made in particular to Figs. 3A-G illustrating a preferred embodiment of a gas restrictor in semi-transparent and 3-dimension view. Fig. 3A illustrates the gas restrictor in a purge configuration. The inflow of beer is illustrated by arrows where one of these arrows are labelled "Beer". As illustrated, the inflow of beer passes through the associated valve V4, which is open, and enters into the chamber through inlet port 5. In Figs. 3A-G, the inlet port 5 is provided as schematically illustrated in Fig. 2. Outflow of foam is also illustrated by arrow where one of these arrow are labelled "Foam". The foam flow out through the gas port 3, pass the associated valve V3, which is open, towards a gas collector. In Fig. 3A a tube 18 connecting the gas restrictor with the keg and a tube 19 connecting the gas restrictor to the beer tap are partly disclosed. The tube 18 is by interior channels formed in the gas restrictor fluidicly connected via to the liquid inlet port 5 and the tube 19 is by interior channels formed in the gas restrictor fluidicly connected through the associated valve V4 to the liquid outlet port 4; the liquid outlet port is most clearly visible in Fig. 3G. Fig. 3B shows a lower section of the gas restrictor in which the interior channels are visible due to the semi-transparent view. Fig. 3B also details the actuators 16 used to operate the associated valves V3 and V4. With reference in particular to Fig. 3B elements of the associated valves are detailed. As seen in Fig. 3B each associated valve a valve stem 20 having a valve disc 21 at one end of the valve stem 20. A seal may be arranged on a surface of the disc 21 facing a port. Such a seal is typically made from rubber and may be attached to the surface of the disc 21 by glue. Alternatively, or in combination, a gasket may be provided for the discs 21 to abut. A flow passage 23 is provided from a valve cavity located above the disc 21 of valve V3 through which passage 23 foam flows toward the gas collector. To seal this passage off, the disc 21 is provided with an O-ring which seals against a valve seat when the valve V3 is closed. In Fig. 3B the valve V3 is shown in a open position whereas the valve V4 is shown in a closed position, that is in purge configuration. Each of valve stems 20 is reciprocatable arranged in the housing 29 between a first position in which the valve disc closes the associated port and a second position in which the valve disc does not close the associated port. In Fig. 3B, valve V3 is open and valve V4 is closed, corresponding to a gas purge configuration. In Fig. 3C valve V3 is closed and valve V4 is closed, corresponding to a gas detected configuration, which is set, when foam is detected in the chamber. It is generally preferred to close valve V4 fast to avoid accumulation of larger quantities of foam in the chamber and / or to limit the risk of foam leaving the chamber 2 through valve V4.. In Fig. 3D valve V3 is closed and valve V4 is open, corresponding to a liquid(beer) dispensing configuration. In Fig. 3E, valve V3 is open and valve V4 is closed (as in Fig. 3A and 3B) corresponding to a gas purge configuration. In the illustrated embodiment of Figs. 3A-G, the reciprocatable movement of the stems 20 is provided by the electrical actuator 16 comprising and electrical motor, which rotates a threaded spindle 24 engaging with a thread provided in a valve body 25 from which the valve stem 20 protrudes. Thus, by powering the electrical motor of the actuator, the spindle 24 rotates which is translated into a translatory motion of the valve body and thereby also the valve stem. A gear box may be included between the electrical motor and the threaded spindle 24 to change the ratio of rotation of the spindle in relation to rotation of the electrical motor. To prevent rotation of the valve body 25 relatively to the housing 29, the valve body 25 has a non-rotational symmetric section which mates a similar shape provided in the housing 29 to prevent rotation of the valve body 25. In the illustrated embodiments, the non-rotational symmetric section has two opposite flat surfaces. Further, the valve body 25 may comprise an O-ring 26, as illustrated, to seal the valve body 25 against the housing 29. Fig. 3E which is a cross sectional view illustrates by arrows the flow of foam through the interior channels during a purge configuration. The valve V3 is shown as open. Fig. 3F which is a cross sectional view illustrates by arrows the flow of liquid (beer) through the interior channels during a liquid dispensing configuration. The valve V4 is shown as open. In some situation, it may be desired to drain the chamber 2 from liquid. To this, the gas restrictor may be configured to drain the chamber 2 from liquid contained in the chamber 2, preferably where the draining is initiated by said controller 7. Such a draining is particular useful prior to a cleaning of the restrictor preferably in combination with cleaning the fluid connection between the gas restrictor and the beer tap and cleaning of the beer tap itself. Such a cleaning can be carried out by instead of connecting the gas restrictor to a keg containing beer, then connecting the gas restrictor to a source of cleaning agent, such as water with ozone, so as to feed the cleaning agent into the chamber 2 through the inlet port 4. By setting the associated valves of the gas restrictor in a liquid dispensing configuration and opening the beer tap, a flow of cleaning agent can be established between the source of cleaning agent, through the gas restrictor and out through the beer tap, to clean these elements of a beer dispensing system. However, as the chamber may contain besides a deposited biofilm beer and / or foam use of for instance water with ozone may result in that the cleaning effect of the water with ozone has been reduced dramatically or even lost during its passage through chamber due to its interaction with the beer and / or foam. However, if the chamber is drained prior to such a cleaning process, the cleaning agent will largely act on the elements, such as deposits, to be cleaned-off. The drainage can be accomplished in a number of ways, and one configuration is schematically illustrated in Fig. 4. In such embodiments, the gas restrictor is configured to provide the drain by the gas pipe 8 being reciprocatable arranged within the chamber 2 between a lower position and an upper position. The lower position corresponds to the position of the gas pipe illustrated in Fig. 1. In the lower position, the lower end of the gas pipe form seals against an outflow passage 15 provided at a bottom of chamber 2. In this position, the gas pipe 8 forms a sealed flow passage from the gas port 3 through the outflow passage 15 and towards the valve V3 associated with the gas port 3. The upper position is disclosed in Fig. 4, and in this position, the lower end of the gas pipe 8 is raised above the outflow passage 15 which provides the illustrated drain passage 10 for flow of liquid and / foam out of the chamber 2 through said outflow passage 15. During draining, the valve V4 is preferably closed and a supply of fluid into the chamber 2 is preferably closed. The gas restrictor may alternatively or in combination with the above be configured to provide the drain by the chamber 2 comprises a drain port 11 being associated with a further electrical or pneumatic controllable shut-off valve vn to control flow of fluid through drain port 11. Such a drain port 11 and further valve vn are illustrated in the embodiment of Fig. 5. The drain port 11 is preferably fluidicly connected to an position being exterior to the chamber 2 and the drain port 11 is preferably provided at a lower end of the chamber 2. In the embodiment shown in Fig. 5, the fluid connection from the valve vn merges with the fluid connection from the valve V3, however this merging is optional and may be left out. Reference is made to Fig. 6 illustrating in 3-dimensional view a system comprising a gas restrictor as illustrated in Figs. 3A-G and a rail 27. In the rail 27 a flow channel 28 is formed and an opening (not illustrated) facing towards the gas restrictor is provided in the rail 27. The opening is through going an provides a opening into the flow channel 28 from a front surface of the rail 27. The gas restrictor is attached to a rail 27 in a position where a channel 23 (see e.g. Fig. 3B) being in fluidic connection with the gas port 3 via the valve V3 associated with the gas port 3, when the valve V3 is open, so as to allow foam being purged from the chamber 2 to flow into said channel 3. The flow channel 28 may preferably be connected to a gas collector. In embodiments of the system comprising a rail, a number of gas restrictors may be attached to the rail, typically side by side. By this, foam may be collected from the attached gas restrictors in parallel and, preferably, fed into a gas collector common for the attached gas restrictors. This is advantageous, since in some applications, a number of different beers are served from a number of different kegs, and gas restriction may be applied to the keg in a easy manner. Preferred embodiments of the invention relates to a method of restricting foam from flowing to a beer tap in a beer dispensing system. Such a beer dispensing system preferably comprises an embodiment of a gas restrictor introduced fluidicly in-between the keg position and the beer tap. The gas restrictor is preferable arranged fluidicly closer to the keg than to the beer tap. The liquid inlet port 5 of the gas restrictor is fluidicly connected via said valve vs associated with the liquid inlet port 5 to a keg 13 to receive beer from the keg 15. The liquid outlet port 4 is fluidicly connected via the valve V4 associated with the liquid outlet port 4 to a beer tap to receive beer flowing into said chamber 2 through said inlet port 5 and out from the chamber though said liquid outlet port 4. In such and other set-ups, the method comprises that • the controller 7 closes the valve V4 associated with said liquid outlet port 4 when the level sensor 6 do not detect the liquid surface at the preselected level such as at the gas port 3. This situation typically occurs when foam has formed inside the chamber as a result of the keg being close to empty. • the controller 7 sets the associated valves in the gas purge configuration upon receipt of a purge instruction. As disclosed above, it is typically an operation (being a human being) which initiates the purge instruction by pushing a button. • the controller 7 sets the associated valves in the liquid dispensing configuration when the level sensor detects the liquid surface at the preselected level, such as at the gas port 3. Preferred embodiments of the method may include a cleaning operation and in such embodiments, the gas restrictor is configured to drain the chamber 2 e.g. as disclosed above in connection with Figs. 4 and 5. During a cleaning operation, the liquid inlet port 5 instead of being fluidicly connected to a keg 13 is fluidicly via the valve vs associated with the liquid inlet port 5 to a source of cleaning agent, such as water with ozone, to receive the cleaning agent from said source. During a cleaning operation the method preferably comprises • the controller 7 receives instructions to successively o close the valve V4 associated with the liquid outlet 4; o drain the chamber 2 from liquid contained in the chamber 2; and o open the valve V4 associated with the liquid outlet 4 and / or open or close valve V3 associated with said gas port 3. Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous. LIST OF REFERENCE SYMBOLS USED 1      Gas restrictor 2    Chamber 3     Gas port 4      Liquid outlet port 5      Inlet port 6     Level sensor 7      Electronic controller 8     Gas pipe 9      Float 10    Drain passage 11    Drain port 12    Inlet pipe 13   Keg 14    Liquid level at gas port 15    Outflow passage 16   Actuator 17    Cylindrical wall 18   Tube (from keg) 19    Tube (to beer tap) 20   Valve stem 21    Valve disc 22   Gasket 23   Channel 24    Spindle 25   Valve body 26    O-ring 27    Rail 28    flow channel 29   Housing V3 Valve associated with gas port V4 Valve associated with liquid outlet port vn Further valve associated with drain port

Claims

1. A gas restrictor for a beverage dispensing system, said gas restrictor device comprising:• a chamber (2) having:o gas port (3) and an liquid outlet port (4) wherein said gas port (3) and said liquid outlet port (4) being associated with an electrical or pneumatic controllable shut-off valve (V3, V4) to control a flow of fluid through said gas port (3) and said liquid outlet port (4) individually from each other;o a liquid inlet port (5)whereino said gas port (3) is situated at position being vertically higher than a vertical position of said liquid outlet port (4),• a level sensor (6) configured to detect that a surface of a liquid contained within said chamber (2) is positioned at a predefined level, preferably being at said gas port (3), and provide an electrical position signal representing that said liquid surface is at said predefined level;• an electronic controller (7) beingo electrical connected with an actuator (16) of each of said associated valves (vs, V4), said actuators being configured to open and close each of said valves (V3, V4) individually by said controller (7) providing an electrical control signal to said actuators,o electrical connected with said level sensor (6) to receive said electrical position signal;• said electronic controller (7) being configured, to set said associated valves (V3, V4) in three configurations:o a gas detected configuration in which said associated valves (V3, V4) both are closed, said gas detected configuration is set by the controller (7) when said liquid surface is below said gas port (3);o a gas purge configuration in which said valve (V3) associated with said gas port (3) is open and said valve (V4) associated with said liquid outlet port (4) is closed, said gas purge configuration being set by the controller receiving a purge instruction, ando a liquid dispensing configuration in which said valve (V4) associated with said liquid outlet port (4) is open and said valve associated with said gas port (3) is closed, said liquid dispensing configuration is set by the controller when said liquid surface is at said predefined level.

2. A gas restrictor according to claim 1, comprising a gas pipe (8) extending upwardly inside said chamber (2), said gas pipe (8) forms said gas port (3) at an upper end of said gas pipe (8) and forms a flow passage from said gas port (3) towards said valve (vs) associated with said gas port (3).

3. A gas restrictor according to claim 1 or 2, comprising a inlet pipe (12) extending upwardly inside said chamber (2), said inlet pipe (12) forms said inlet port (5) at an upper end of said inlet pipe (12) and forms a flow passage into said chamber (2).

4. A gas restrictor according to any one of the preceding claims, wherein said liquid outlet port (4) is arranged in a vertically lower position than a position of said inlet port (5).

5. A gas restrictor according to any one of the preceding claims, wherein said level sensor (6) being arranged inside and at an upper end of said chamber (2) and comprises• a float (9) being moveable between at least an upper and a lower position, and • a pick-up device being configured to provide an electrical position signal representing that the float (9) is in said upper position;wherein• said upper position is a position of the float (9) provided by said liquid surface being at said gas port (3), and• said lower position is a position of the float (9) provided by said liquid surface being below said gas port (3).

6. A gas restrictor according to claim 5, wherein said float has a density smaller than a density of water, and larger than 5%, such as larger than 10%, preferably larger than 15% of the density of water.

7. A gas restrictor according to any one of the preceding claims, wherein a volume of said chamber (2) above said gas port (3) is smaller than 10%, such as smaller than 5%, preferably smaller than 2% of a total volume of said chamber (2).

8. A gas restrictor according to any one of the preceding claims, wherein a total interior volume of said chamber (2) is between 80 cm3 and 200 cm3 , such as between 100 cm3 and 150 cm3.

9. A gas restrictor according to any one of the preceding claims, configured to drain said chamber (2) from liquid contained in the chamber (2) wherein said draining is initiated by said controller (7).

10. A gas restrictor according to claim 9, when dependant on claim 2, wherein said gas restrictor is configured to provide said drain by said gas pipe (8) being reciprocatable arranged within said chamber (2) between• a lower position in which a lower end of said form seals against an outflow passage (15) at a bottom of said chamber (2) and said gas pipe (8) forms a flow passage from said gas port (3) through said outflow passage (15) and towards said valve (vs) associated with said gas port (3) and,• an upper position in which said lower end is raised above said outflow passage (15) to provide a drain passage (10) for said liquid out of said chamber (2) through said outflow passage.

11. A gas restrictor according to claim 9, wherein said gas restrictor is configured to provide said drain by said chamber (2) comprising a drain port (11) being associated with a further electrical or pneumatic controllable shut-off valve (vn) to control flow of fluid through said drain port (11) wherein said drain port (11) is fluidicly connected to an position being exterior to the chamber (2), said drain port (11) is preferably provided at a lower end of said chamber (2).

12. A system comprising a gas restrictor according to any one of the preceding, and a rail (27) in which an flow channel (28) is formed having an opening facing towards the gas restrictor and wherein the gas restrictor is attached to said rail (27) in a position where a channel (23) being in fluidic connection with said gas port (3) via said valve (V3) associated with said gas port (3), when said valve (V3)is open, so as to allow gas being purged from said chamber (2) to flow into said channel (3).

13. A method of restricting gas from flowing to a beverage tap in a beverage dispensing system comprising a gas restrictor according to any one of the preceding claims 1-11, wherein• said liquid inlet port (5) is fluidicly via said valve (vs) associated with the liquid inlet port (5) to a keg (13) to receive beverage from said keg (15);• said liquid outlet port (4) is fluidicly connected via said valve (V4) associated with said liquid outlet port (4) to a beverage tap to receive beverage flowing into said chamber (2) through said inlet port (5) and out from said chamber though said liquid outlet port (4), said method comprises• said controller (7) closes said valve (V4) associated with said liquid outlet port (4) when said level sensor (6) do not detect said liquid surface at said gas port (3);• said controller (7) sets said associated valves in said gas purge configuration upon receipt of a purge instruction;• said controller (7) sets said associated valves in said liquid dispensing configuration when said level sensor detects said liquid surface at said gas port (3).

14. A method according to claim 13, wherein said gas restrictor is according any one of the preceding claims, when dependant on claims 9-11, and wherein said liquid inlet port (5) instead of being fluidicly connected to a keg (13) is fluidicly via said valve (vs) associated with the liquid inlet port (5) to a source of cleaning agent, such as water with ozone, to receive said cleaning agent from said source; said method comprising• said controller (7) receives instructions to successivelyo close said valve (V4) associated with said liquid outlet (4);o drain of said chamber (2) from liquid contained in the chamber (2); and o open said valve (4) associated with said liquid outlet (4) and / or open or close said valve (vs) associated with said gas port (3).

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