Abstract:
In a device for infusing a gas from a gas source into a liquid beverage, a beverage container defines an interior for holding the liquid beverage therein. A venturi mixing device has a liquid inlet port in fluid communication with the beverage container, a gas inlet port in fluid communication with the gas source and a discharge port. The venturi mixing device is configured to infuse the gas received from the gas source into liquid beverage received from the beverage container. A faucet is in fluid communication with the discharge port of the venturi mixing device and is configured to dispense the liquid beverage infused with the gas.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/309,006, filed Mar. 16, 2016, the entirety of which is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to systems and methods for liquid beverage dispensing and, more specifically, to systems and methods for infusing compressed gases such as nitrogen into chilled beverages such as coffee, and dispensing the gas-infused chilled beverages in a manner that causes a pleasing head of foam to be created and maintained on the surface of the beverage during and after dispensing into a receiving container. 
         [0004]    2. Description of the Related Art 
         [0005]    The storing and dispensing of chilled beverages using compressed nitrogen and other gases is used to generate a pleasing head of foam to form on the surface of beverages when they are dispensed into a cup or a mug. Existing nitrogen infusion typically employ porous membranes or other elaborate and bulky mixing components cause such infusion. Many such systems require gas permeable membranes that are subject to clogging. Other systems employ elaborate liquid and gas mixing schemes, which include multiple regulated liquid and gas pressures to achieve the desired gas infusion in combination with an acceptable dispensing rate and a desired appearance. 
         [0006]    Thus, there is a need for chilled beverage gas-infusion and dispensing systems and methods that are simpler, have fewer components and are therefore easier to maintain, more reliable and have a lower cost than existing systems. 
         [0007]    There is also a need for gas-infusion and dispensing systems and methods that consistently provide a high density, long-lasting head on dispensed chilled coffee. 
         [0008]    There is also a need for gas-infusion and dispensing systems and method that provide a user-selectable proportion of head-to-settled liquid. 
         [0009]    There is also a need for gas-infusion and dispensing systems and methods that infuse increased proportions of gas compared to existing systems, thereby providing a proportion of head-to-settled liquid, and a head density that is considered most appealing to those consuming the beverage. 
       SUMMARY OF THE INVENTION 
       [0010]    The disadvantages of the prior art are overcome by the present invention which, in one aspect, is a device for infusing a gas from a gas source into a liquid beverage. A beverage container defines an interior for holding the liquid beverage therein. A venturi mixing device has a liquid inlet port in fluid communication with the beverage container, a gas inlet port in fluid communication with the gas source and a discharge port. The venturi mixing device is configured to infuse the gas received from the gas source into liquid beverage received from the beverage container. A faucet is in fluid communication with the discharge port of the venturi mixing device and is configured to dispense the liquid beverage infused with the gas. 
         [0011]    In another aspect, the invention is a coffee serving device that includes a nitrogen tank, a pressure regulator, a coffee tank, a flow restricting device and a venturi mixing device. The pressure regulator is in fluid communication with the nitrogen tank. The coffee tank defines an interior for holding liquid coffee therein. An input fitting that is in fluid communication with the interior of the coffee tank couples the coffee tank to the pressure regulator. An output fitting is in fluid communication with the interior of the coffee tank. The coffee tank is configured so that gas pressure received through the input fitting forces coffee out of the beverage container through the output fitting. A flow restricting device is in fluid communication with the first pressure regulator. A venturi mixing device has a liquid inlet port in fluid communication with the output fitting, a gas inlet port in fluid communication with the flow restricting device and a discharge port. The venturi mixing device is configured to infuse nitrogen received through the flow restricting device into the coffee received from the output fitting of the beverage container. A faucet is in fluid communication with the discharge port of the venturi mixing device and is configured to dispense the coffee infused with nitrogen. 
         [0012]    In yet another aspect, the invention a method of serving nitrogen-infused liquid beverage, in which liquid beverage is driven from a beverage container into a liquid inlet port of a venturi mixing device. Nitrogen is infused into the liquid beverage by driving nitrogen through a gas inlet port of the venturi mixing device, thereby delivering nitrogen-infused liquid beverage to a discharge port of the venturi mixing device. The nitrogen-infused liquid beverage is poured from the discharge port through a faucet. 
         [0013]    These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be obvious to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic diagram of a first embodiment of a beverage gas-infusion and dispensing system. 
           [0015]      FIG. 2  is a schematic diagram of a second embodiment of a beverage gas-infusion and dispensing system. 
           [0016]      FIG. 3  is a schematic diagram of a third embodiment of a beverage gas-infusion and dispensing system. 
           [0017]      FIG. 4  is a flow chart showing one method of nitrogen-infusing and dispensing a beverage. 
           [0018]      FIG. 5  is a flow chart showing a method of gas-infusing and dispensing a beverage. 
           [0019]      FIG. 6  is a schematic diagram of a beverage dispensing faucet assembly. 
           [0020]      FIG. 7  is a schematic diagram of a first example of a venturi mixing device. 
           [0021]      FIG. 8  is a schematic diagram of a second example of a venturi mixing device. 
           [0022]      FIG. 9  is a schematic diagram of a third example of a venturi mixing device. 
           [0023]      FIG. 10  is a chart that illustrates the percent volume of settled head versus the amount of infused nitrogen for a particular chilled coffee beverage that is dispensed. 
           [0024]      FIG. 11  is a tabulation of data and results from dispensing experiments conducted with one representative embodiment of the invention. 
           [0025]      FIG. 12  is a chart that illustrates equivalent orifice sizes associated with the acceptable and desired ranges of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. Unless otherwise specifically indicated in the disclosure that follows, the drawings are not necessarily drawn to scale. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.” 
         [0027]    As shown in  FIG. 1 , a gas infusion system  100  includes a pressured gas cylinder  104  that contains a gas or a gas mixture, which in one embodiment includes pure or substantially pure nitrogen. A pressure regulator  109  provides a regulated flow of gas into line  108  at a predetermined pressure. Typically, the regulator  109  would maintain gas pressure within the range of about 15 psi to 80 psi. In one embodiment, the regulator  109  maintains the gas pressure in a range of about 25 psi to 35 psi and in one specific embodiment it maintains the gas pressure within a range of about 28 psi to 32 psi. Depending on the specific application, the gas cylinder  104  may be located near to the beverage faucet assembly  101 . In some applications, the gas cylinder  104  may be located away from beverage faucet assembly  101  for safety reasons. An optional secondary pressure regulator  107  may be provided near beverage faucet assembly  101  as a convenience, whereby the regulated pressure may be easily adjusted. 
         [0028]    Line  108  or optional regulator  107  (if used), connects to lines  114 A and  114 B. Line  114 B connects to an inlet port of pressurized beverage tank  102 , where the connection may utilize a quick disconnect fitting  105  of a type that is well known in the beverage industry. Line  114 A connects to the inlet port of a flow restricting device, such as valve  132 V. A flow restricting orifice  1320  may be used in place of valve  132 V, and other types of gas flow restricting devices may also be used. In one embodiment, a precision needle valve may be used. 
         [0029]    The exit port of valve  132 V is connected to line  116  which connects to the suction inlet  140 S of venturi mixing device  140 . Line  115  connects the exit port of beverage tank  102  to pressure inlet port  140 P of venturi mixing device  140 . Line  111  connects exit port  140 E of venturi mixing device  140  to beverage faucet assembly  101 . When faucet  103  is closed, pressures within system  100  are in equilibrium. Check valves or ball valves (not shown) may be used in line  115  to prevent reverse flow (or shut off flow) of beverage from mixing device  140  into line  115  toward tank  102 , and/or in line  116  to prevent reverse flow (or shut off flow) of gas, liquid beverage, or both through suction port  140 S into line  116 . 
         [0030]    To dispense a gas-infused beverage, an operator moves faucet handle  118  to a partially-open or fully-open position. This allows pressurized gas within line  108  and then line  114 B to displace liquid beverage from tank  102  causing liquid beverage to flow from the exit port of tank  102  into line  115 . Tank  102  may be located within a refrigerator or refrigeration unit as commonly known in the beverage industry. Liquid beverage in line  115  then flows into pressure inlet port  140 P of venturi mixing device  140 . Simultaneously, pressurized gas in line  114 A flows into and through valve  132 V, exiting at a reduced pressure into line  116  and then flowing into suction inlet  1405 . Within venturi mixing device  140 , liquid beverage flows through a reduced cross-sectional area flow restriction adjacent suction inlet  140 S as is well known for venturi mixing devices. The flow restriction causes a higher velocity and reduced static pressure within the beverage flow. The reduced static pressure entrains gas within line  116  and infuses the gas into the beverage flow. The gas-infused beverage exits port  140 E into line  111 . Finally, the gas-infused beverage flows through line  111  and is dispensed from faucet  103  into a receiving container. 
         [0031]    As shown in  FIG. 2 , an alternate embodiment of a gas infusion system  200  employs a beverage bag  216  to hold the beverage. Beverage bags are commercially available in various sizes and with different materials of construction. Generally, a container of 1 to 5 gallons is utilized for the present invention, but any suitable container of size convenient to the intended application may also be utilized. A pressured gas cylinder  204  contains a gas or a gas mixture, preferably pure or substantially pure nitrogen. Pressure regulator  209  provides a regulated flow of gas into line  208  at a predetermined pressure. In one embodiment, an acceptable pressure within a range of about 15 psi to 80 psi, in certain applications the pressure is within a range of about 25 psi to 35 psi, and in certain specific applications the pressure is within a range of about 28 psi to 32 psi. Gas cylinder  204  may be located near to, or remotely from beverage faucet assembly  201 . Gas cylinder  204  may be located in a remote location, away from beverage faucet assembly  201  for safety reasons. Optional secondary pressure regulator  207  may be provided near beverage faucet assembly  201  as a convenience, whereby the regulated pressure may be easily adjusted. Line  208  or optional regulator  207  (if used), connects to line  214 A. Line  214 A connects to the inlet port of a flow restricting device, illustrated as valve  232 V. A flow restricting orifice  2320  may be used in place of valve  232 V, and other types of gas flow restricting devices may also be used. The exit port of valve  232 V is connected to line  216  which connects to the suction inlet  240 S of venturi mixing device  240 . Line  215  connects the exit port of flexible beverage bag  216  to the inlet port of pump  210 . Beverage bag  216  may be contained in a box (not shown). The box may be corrugated cardboard while the bag  216  may be constructed of any material accepted for use in the food and beverage industry. Pump  210  may be an air driven diaphragm pump as commonly known in the beverage industry, optionally driven using compressed gas from gas cylinder  204 . Pump  210  may also be another type of pump such as an electrically-driven pump configured to operate when faucet handle  218  is partially or fully opened. The exit port of pump  210  connects to pressure inlet port  240 P of venturi mixing device  240 . Line  211  connects exit port  240 E of venturi mixing device  240  to beverage faucet assembly  201 . When faucet  203  is closed, pressures within system  200  are in equilibrium. Check valves (not shown) may be used to in line  215  to prevent reverse flow of beverage from mixing device  240  into line  115  toward pump  210 , and/or in line  216  to prevent reverse flow of gas, liquid beverage, or both through suction port  240 S into line  216 . To dispense a gas-infused beverage, an operator moves faucet handle  218  to a partially-open or fully-open position. This causes pump  210  to operate and displace liquid beverage from bag  216  into line  215 , through pump  210 , flowing though the pump exit port and then into pressure inlet port  240 P of venturi mixing device  240 . Simultaneously, pressurized gas in line  208  and then line  214 A flows into and through valve  232 V, exiting at a reduced pressure into line  216  and then flowing into suction inlet  240 S. Within venturi mixing device  240 , liquid beverage flows through a reduced cross-sectional area flow restriction adjacent suction inlet  240 S as is well known for venturi mixing devices. The flow restriction causes a higher velocity and reduced static pressure within the beverage flow. The reduced static pressure entrains gas within line  216  and infuses the gas into the beverage flow. The gas-infused beverage exits port  240 E into line  211 . Finally, the gas-infused beverage flows through line  211  and is dispensed from faucet  203  into a receiving container. Bag  216  may be located within a refrigerator or refrigeration unit as commonly known in the beverage industry. 
         [0032]    Another embodiment of a beverage dispensing system  300  is shown in  FIG. 3 . A pressured gas cylinder  304  contains a gas or a gas mixture, which can be pure or substantially pure nitrogen. Pressure regulator  309  provides a regulated flow of gas into line  308  at a predetermined pressure. An acceptable pressure includes a pressure within the range of about 15 psi to 80 psi, in certain applications the pressure is within a range of about 25 psi to 35 psi, and in certain specific applications the pressure is within a range of about 28 psi to 32 psi. Gas cylinder  304  may be located near to, or remotely from beverage faucet assembly  301 . Gas cylinder  304  may be located in a remote location, away from beverage faucet assembly  301  for safety reasons. Optional secondary pressure regulator  307  may be provided near beverage faucet assembly  301  as a convenience, whereby the regulated pressure may be easily adjusted. Line  308  or optional regulator  307  (if used), connects to lines  314 A and  314 B. A flexible beverage bag  350  is contained by a semi-rigid container  352  such as a cardboard box, comprising a structurally-constrained bag-in-box arrangement. One example of such a bag-in-box arrangement is disclosed in U.S. Pat. No. 4,796,788 to Bond, which is incorporated herein by reference. Container  352  is sized to fit within a structurally rigid container  352  with a lid  356  suitably attached using a hinge or other fastening arrangement. Beverage bag  350  can include two layers, with an inner layer to contain a liquid beverage, a separate outer layer surrounding the inner layer, a beverage outlet port  355  that connects to the volume formed by the bag inner layer, and a pressure inlet port  354  that connects to the volume formed between the bag layers. The outer layer of the bag is confined by container  352 , and introduction of the pressurized gas through port  353  from line  314 B causes the bag inner layer to be compressed thereby causing an outlet flow of beverage from beverage outlet port  355 . Line  314 A connects to the inlet port of a flow restricting device, illustrated as valve  332 V. A flow restricting orifice  3320  may be used in place of valve  332 V in certain applications, and other types of gas flow restricting devices well known to the art may also be used. The exit port of valve  332 V is connected to line  316  which connects to the suction inlet  340 S of venturi mixing device  340 . Line  315  connects the exit port  355  of beverage bag  350  to pressure inlet port  340 P of venturi mixing device  140 . Line  311  connects exit port  340 E of venturi mixing device  340  to beverage faucet assembly  301 . When faucet  303  is closed, pressures within system  300  are in equilibrium. Check valves (not shown) may be used in line  315  to prevent reverse flow of beverage from mixing device  340  into line  315  toward bag  350 , and/or in line  316  to prevent reverse flow of gas, liquid beverage, or both through suction port  340 S into line  316 . To dispense a gas-infused beverage, an operator moves faucet handle  318  to a partially-open or fully-open position. This allows pressurized gas within line  308  and then line  314 B to displace liquid beverage from bag  350  causing liquid beverage to flow from bag exit port  355  into line  315 . Liquid beverage in line  315  then flows into pressure inlet port  340 P of venturi mixing device  340 . Simultaneously, pressurized gas in line  314 A flows into and through valve  332 V, exiting at a reduced pressure into line  316  and then flowing into suction inlet  340 S. Within venturi mixing device  340 , liquid beverage flows through a reduced cross-sectional area flow restriction adjacent suction inlet  340 S as is well known for venturi mixing devices. The flow restriction causes a higher velocity and reduced static pressure within the beverage flow. The reduced static pressure entrains gas within line  316  and infuses the gas into the beverage flow. The gas-infused beverage exits port  340 E into line  311 . Finally, the gas-infused beverage flows through line  311  and is dispensed from faucet  303  into a receiving container. Container  352  may be located within a refrigerator or refrigeration unit as commonly known in the beverage industry. 
         [0033]      FIG. 4  illustrates a method  400  to nitrogen-infuse and dispense a beverage which could be employed using the embodiments shown in  FIGS. 1 and 3 . Step  402  includes providing a regulated pressurized source of pure or substantially pure nitrogen; a beverage storage vessel; a venturi mixing device with a pressure inlet port, a suction inlet port and exit port; a throttling device; and a beverage faucet. Step  404  includes utilizing the regulated source of nitrogen to induce a pressurized flow of liquid beverage from a storage vessel into the pressure inlet of the venturi mixing device. Step  406  includes utilizing the same regulated source of nitrogen to cause a flow of nitrogen through the throttling device to cause a reduced-pressure nitrogen flow. Step  408  includes supplying the reduced-pressure nitrogen flow to the suction inlet of the venturi mixing device. Step  410  includes mixing the liquid beverage and reduced-pressure nitrogen flow within the venturi mixing device to obtain a nitrogen infused liquid beverage. Step  412  includes supplying the nitrogen-infused liquid beverage to a beverage faucet and dispensing into a receiving container. 
         [0034]    In one embodiment of a gas infusion method  500 , as shown in  FIG. 5 , step  502  includes providing a regulated pressurized source of pure or substantially pure gas; a pump; a beverage storage vessel; a venturi mixing device with a pressure inlet port, a suction inlet port and exit port; a throttling device; and a beverage faucet. Step  504  includes utilizing the pump to induce a pressurized flow of liquid beverage from the storage vessel into the pressure inlet of the venturi mixing device. Step  506  includes utilizing the regulated source of gas to cause a flow of gas through the throttling device to cause a reduced-pressure gas flow. Step  508  includes supplying the reduced-pressure gas flow to the suction inlet of the venturi mixing device. Step  510  includes mixing the liquid beverage and reduced-pressure gas flow within the venturi mixing device to obtain a nitrogen infused liquid beverage. Step  512  includes supplying the gas-infused liquid beverage to a beverage faucet and dispensing into a receiving container. 
         [0035]    One embodiment of a dispensing faucet assembly is shown in  FIG. 6 , in which a beverage faucet  601  can include a slow pour faucet  603  equipped with tap handle  618 . Faucet  603  can also be equipped with a restrictor nozzle  617  which can further include a restrictor disc (not shown) as commonly known in the beverage industry for dispensing stout beers. Beverage faucet  601  may help provide a high density, long-lasting settled head on chilled coffee dispensed according to embodiments of the present invention, in particular when operated using predetermined pressures and temperatures. Beverage faucet  601  may also comprise multiple slow pour faucets for dispensing multiple beverages from a single location. 
         [0036]    A first example of a venturi mixing device  740 , as shown in  FIG. 7 , includes pressure inlet port  740 P, suction inlet port  740 S, flow restriction  740 T and exit port  740 E. Pressurized liquid beverage enters through pressure inlet port  740 P and pressurized gas enters through suction inlet port  740 S. Within venturi mixing device  740 , liquid beverage flows through flow restriction  740 T with a reduced cross-sectional area as is well known for venturi mixing devices. Flow restriction  740 T causes a higher velocity and reduced static pressure within the beverage flow adjacent port  740 S which entrains gas entering through port  740 S and infuses the gas into the beverage flow. The gas-infused beverage exits device  740  through exit port  740 E. U.S. Pat. No. 2,210,846 to Aghnides, U.S. Pat. No. 2,571,870 to Hayes, and U.S. Pat. No. 2,800,313 to Targosh et al. illustrate venturi mixing devices or eductors and are incorporated herein by reference for the purpose of showing venturi/eductor devices and methods of making such devices. 
         [0037]    A second example of a venturi mixing device  840 , as shown in  FIG. 8 , includes pressure inlet port  840 P, suction inlet port  840 S, flow restriction  840 T and exit port  840 E. Pressurized liquid beverage enters through pressure inlet port  840 P and pressurized gas enters through suction inlet port  840 S. A nozzle  840 N may be present and protrude into flow restriction  840 T. Within venturi mixing device  840 , liquid beverage flows through flow restriction  840 T with a reduced cross-sectional area as is well known for venturi mixing devices. Flow restriction  840 T causes a higher velocity and reduced static pressure within the beverage flow adjacent port  840 S which entrains gas entering through port  840 S and infuses the gas into the beverage flow. Nozzle  840 N may enhance the gas infusion into the liquid beverage. The gas-infused beverage exits device  840  through exit port  840 E. 
         [0038]    A third example of a venturi mixing device  940 , as shown in  FIG. 9 , includes an eductor that includes pressure inlet port  940 P, suction inlet port  940 S, flow nozzle  940 T and exit port  940 E. Pressurized liquid beverage enters through pressure inlet port  940 P and pressurized gas enters through suction inlet port  940 S. Within venturi mixing device  940 , liquid beverage flows through flow nozzle  940 T with a reduced cross-sectional area as is well known for eductors. Flow nozzle  940 T causes a higher velocity and reduced static pressure within the beverage flow adjacent port  940 S which entrains gas entering through port  940 S and infuses the gas into the beverage flow. The gas-infused beverage exits device  940  through exit port  940 E. In one embodiment, the eductor could include a T-fitting. 
         [0039]    A venturi mixing device may be fabricated as a single unit as illustrated in  FIGS. 7 through 9 , or may be assembled using commonly available pipe or tube fittings. For example, a venturi mixing assembly may be constructed of a standard tee fitting and two reduction fittings, wherein the small ends of the reduction fittings are sized to match the ends of the tee fittings. The small ends of the first and second reduction fittings are assembled to either end of the tee fitting. When used in the present invention, the liquid beverage flows into the large end and then the small end of the first reduction fitting, through the tee fitting and past the right-angle port of the tee, through the small end of the second reduction fitting and then exits through the large end of the second reduction fitting. The reduced cross-sectional area within the tee fitting creates higher velocity and reduced static pressure within the beverage flow adjacent the right-angle port of the tee fitting, and thus the right angle port of the tee functions as the suction inlet of the venturi mixing assembly. In this manner a venturi mixing assembly may be assembled from inexpensive pipe or tube fittings which may be lower cost as compared to single unit venturi mixing devices. 
         [0040]    Embodiments of the present invention include components that can cooperate to gas-infuse, dispense and provide a pleasing proportion of settled head on a liquid beverage. The volume of the settled head produced by embodiments of the present invention can be greater than about fifteen percent, greater than about twenty five percent, and can also be about thirty percent of the total volume occupied by the settled head and the underlying liquid beverage within a receiving container. The liquid beverage may be dispensed using a pressure within the range of about 15 psi to 80 psi, and in one embodiment within a range of about 25 psi to 45 psi, and in a specific embodiment within a range of about 28 psi to 32 psi. In some embodiments, the liquid beverage is cooled to a temperature of about 33° F. to 40° F. prior to dispensing. In other embodiments, the liquid beverage is coffee that is cooled to a temperature of about 34° F. to 37° F. prior to dispensing. The volume of the settled head may be adjusted by a user and can depend upon the pressure and temperature of the chilled beverage as well as the design of the individual components that comprise various embodiments of the present invention. 
         [0041]    The percent volume of settled head versus the amount of infused nitrogen for a particular chilled coffee beverage that is dispensed according to embodiments of the invention is shown in  FIG. 10 . The solid diamond symbols represent performance for predetermined pressures and temperatures, the solid circle symbols represent performance for other pressures and temperatures that fall within the scope of the present invention. (The solid triangle symbols represent performance for particular experiments conducted at about 35 psi regulated gas pressure, liquid beverage temperature of about 35° F., and liquid beverage flow of about 0.28 U.S. gallons per minute.) According to  FIG. 10 , for this particular beverage a settled head of greater than about fifteen percent volume requires nitrogen infusion greater than about 100 parts per million (ppm) by weight. A settled head of greater than about twenty five percent requires nitrogen infusion greater than about 220 ppm. A settled head of about thirty percent requires nitrogen infusion greater than about 250 ppm. Now referring to  FIG. 1 , flow restricting device  132 V or  132 O can be designed to cooperate with a membrane-free eductor  140  (such as a venturi) to infuse nitrogen into a liquid beverage at greater than about 100 ppm by weight for an embodiment of the invention, greater than about 160 ppm for one example of an embodiment of the invention, and greater than about 250 ppm for another example of an embodiment of the invention. Other types of beverages may require differing amounts of infused nitrogen to provide a desired percentage of settled head. One beverage may have a differing amount of total dissolved solids (TDS) than another beverage, and the TDS may influence the volume of settled head. Increased TDS in a beverage may result in reduced settled head and vice versa. 
         [0042]    A tabulation of data and results from dispensing experiments conducted with a first embodiment of the invention is shown in  FIG. 11 . In these experiments, gas and liquid flow meters were inserted into lines  114 A and  115  (as shown in  FIG. 1 ), respectively, to measure the infusing gas flow and liquid beverage flow, respectively. For example, in one experiment the infusing gas was nitrogen, and the liquid beverage was chilled coffee. The regulated gas pressure was about 35 psi, and the chilled coffee temperature was about 35° F. The measured chilled coffee flow was about 0.28 U.S. gallons per minute (GPM), and the measured nitrogen flow was about 0.35 standard cubic feet per hour (SCFH). Dividing the nitrogen flow by the chilled coffee flow results in a ratio of about 1.25 SCFH/GPM. The calculated gas flow (and nitrogen infusion) for this experiment on a weight basis is about 200 ppm. Performance for various embodiments of the invention at various dispensing conditions is described in  FIG. 11 . 
         [0043]    The flow restricting device  132 V or  132 O is designed to operate with venturi mixing device  140  using known design rules for fluid flow through such devices. Embodiments of the invention can include a flow control orifice  132 O with a diameter of less than about 0.05 inches for use with a venturi mixing device  140  that has a through-flow of about 1 U.S. gallons per minute or less at predetermined pressures and temperatures. Embodiments of the invention can include a precision needle valve to provide a user-adjustment for infused nitrogen and thus a means to control and adjust the amount of settled head. Other orifice and venturi mixing device sizes and designs fall within the scope of the present invention. 
         [0044]    As shown in  FIG. 12 , equivalent orifice sizes are associated with the acceptable and predetermined ranges of  FIG. 11 . The shaded area  1200  represents the acceptable range; the cross-hatched area  1202  represents the predetermined range. As discussed above, the flow restricting device can include valve  132 V or orifice  132 O. Valve  132 V can include a precision needle valve. The equivalent orifices sizes in  FIG. 12  can represent the characteristics of valve  132 V when adjusted to provide the flow of an orifice of a desired diameter. Embodiments of the invention can include a flow restricting device with flow performance equivalent to orifices ranging in diameter from about 0.005 inches to about 0.015 inches. For example, the horizontal line  1204  drawn at 0.009 inches in  FIG. 12  can represent an orifice  132 O of 0.009 inches diameter or a valve  132 V adjusted to provide the same flow as a 0.009 inch diameter orifice. The gas flow thus provided results in gas infusion of about 175 ppm to about 250 ppm on a weight basis for liquid beverage flows of about 1 to about 0.28 U.S. gallons per minute, respectively. 
         [0045]    The pressures and temperatures disclosed herein can create conditions favorable for dispensing the beverage through a slow pour faucet as previously described. As the nitrogen-infused beverage exits the faucet nozzle, the infused nitrogen undergoes a volume expansion of about 2.7-to-1 (at 25 psi regulated pressure) to about 3.4-to-1 (at 35 psi regulated pressure) as the infused nitrogen equilibrates to ambient pressure. At these pressures a settled head with a pleasing creamy texture is formed. Higher pressures may cause expansion that is too large and/or too rapid, thereby causing excessive foam and/or faucet sputtering. Lower pressures may cause insufficient head with a less-creamy texture. 
         [0046]    The above described embodiments, while including the preferred embodiment and the best mode of the invention known to the inventor at the time of filing, are given as illustrative examples only. It will be readily appreciated that many deviations may be made from the specific embodiments disclosed in this specification without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is to be determined by the claims below rather than being limited to the specifically described embodiments above.