Abstract:
A method and apparatus for mixing fluids, such as beverage syrup and water, uses countercurrent injection to improve blending of the fluids. A mixing chamber has a first inlet through which a first fluid is fed to the mixing chamber, and a second inlet through which a countercurrent injection nozzle extends and is operative to inject a second fluid into a stream of the first fluid. The countercurrent injection nozzle is equipped with a check valve to control the flow of fluid into the mixing chamber. The mixing chamber may include additional inlets that may be fitted with countercurrent injection nozzles to permit the countercurrent injection of other fluid, such as flavorings, into the stream of the first fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Ser. No. 61/164,688 filed Mar. 30, 2009, the disclosure of which is incorporated herein. 
    
    
     FIELD OF INVENTION 
     The present invention is directed to blending systems and, more particularly, to a method and system of blending fluids using countercurrent injection. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Liquid blending systems, such as those used to mix beverage syrup and water, typically introduce a stream of beverage syrup and a stream of liquid such as water to a mixing chamber. In the mixing chamber, the syrup and the liquid mix with one another to provide a partially blended beverage. The partially blended beverage typically then flows to a static diffuser, which functions to fully blend the beverage. One type of diffuser includes a series of plates in a stacked arrangement. The partially blended beverage is radially expanded by the surface of the plates, and the spaced arrangement of the plates causes a cascading effect of the beverage through the diffuser. The beverage is subjected to an expanding and shearing process as it passes through diffuser, which ultimately results in a fully blended beverage. 
     One of the drawbacks of conventional beverage blending systems is the lack of blending that occurs within the mixing chamber upstream of the diffuser. That is, most of the mixing of the beverage syrup and the liquid occurs at the static diffuser rather than from the introduction of beverage syrup to the flow of liquid, or vice-versa. While there may be some dispersion of the beverage syrup into the stream of liquid, or vice-versa, for the most part, these separate components remain relatively separate from one another until presented to the diffuser, which can result in a syrup slug being presented to the diffuser. While the diffuser will expand the slug and provide a certain amount of blending, it is possible for the slug to overwhelm the diffuser and result in a poorly blended beverage. 
     Poor mixing of syrup and liquid can result in an incorrect ratio of syrup to liquid medium. In the past, any such imbalances have been accounted for by passing the syrup and liquid through an averaging tank. While this functions satisfactorily to even out liquid/syrup ratios, it involves an added piece of equipment that requires installation and maintenance, as well as an additional step in the process. 
     In addition, conventional blending systems have utilized pump control to regulate the flow of syrup and liquid along respective supply conduits to the mixing chamber. Nipple valves are usually provided at the dispensing ends of each supply conduit. When the pumps are shut off at the end of a dispensing cycle, forced flow of syrup and liquid along the supply: conduits ceases. However, because of the density of the syrup, it is not uncommon for some syrup to leak out of the nipple valve into the mixing chamber. If the liquid medium is also leaked into the mixing chamber, the leakage of syrup would be less problematic. However, the less dense liquid medium typically does not leak past the nipple valve at the end of the liquid supply conduit. The introduction of residual of syrup to the mixing chamber can disturb the ratio of syrup and liquid in the mixing chamber when the dispenser is cycled back on. 
     The above-described lack of precision in controlling the amounts of syrup and liquid medium can be exaggerated when additional ingredients are added, such as flavoring or the like. 
     The present invention seeks to overcome the drawbacks of conventional blending systems by providing a blending system that uses countercurrent injection to improve the blending of a concentrate, such as beverage syrup, with a fluid medium, such as water. Introducing concentrate and fluid in opposed flows into a mixing area improves the dispersion or blending of concentrate in the liquid medium, which provides more efficient and better blending downstream, such as by a static diffuser. 
     Additionally, in one embodiment, respective check valves are used to control the flow of concentrate and liquid medium from respective supply conduits into the mixing chamber. The check valves provide improved performance against backflow and leakage. 
     The present invention also reduces the occurrence of syrup (or concentrate) slugs, provides consistent pre-diffuser distribution of concentrate, and eliminates the need for large averaging tanks typically required in beverage blending systems. 
     Therefore, in accordance with one aspect of the invention, a fluid mixing apparatus for mixing a first fluid and a second fluid is provided. The mixing apparatus includes a mixing chamber having an inlet and an outlet, with the inlet designed to pass a stream of the first fluid along a first flow direction. A countercurrent injection nozzle is disposed within the mixing chamber and is operative to inject the second fluid into the stream of the first fluid along a second flow direction that opposes the first flow direction. As the second fluid exits the countercurrent injection nozzle, the second fluid collides with the first fluid and causes turbulent flow of the two fluid components within the mixing chamber. This collision and turbulent flow causes immediate dispersion of the second fluid and, ultimately, distribution of particles of the second fluid within the first fluid. 
     In accordance with another aspect of the invention, a multi-stage blending system is provided, and includes a mixing chamber having a fluid inlet and a fluid outlet. The fluid inlet is configured to receive a primary fluid stream. The system further includes a plurality of spaced valve bodies arranged between the fluid inlet and the fluid outlet. A respective mixing volume is defined between successive valve bodies. Each mixing volume has a respective countercurrent injection nozzle that is configured to inject a secondary fluid into the primary fluid stream. Thus, within each mixing volume, the collision of the secondary fluid into the primary fluid stream is used to distribute the secondary fluid throughout the primary fluid stream. 
     The present invention may also be embodied in a method. Accordingly, another aspect of the invention includes a method of mixing a first fluid and a second fluid. The method includes introducing a first fluid into a mixing chamber having an outlet and introducing a second fluid into the mixing chamber along a flow path that opposes the flow path along which the first fluid flows within the mixing chamber toward the outlet. 
     It is therefore an object of the invention to provide a blending system providing improved blending. 
     It is another object of the invention to provide a blending system that does not include an averaging tank. 
     It is another object of the invention to provide a beverage blending system with reduced leakage of concentrate into a mixing chamber. 
     Other objects, features, aspects, and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout. 
       In the drawings: 
         FIG. 1  is a is a schematic diagram of a blending system in a general application according to one embodiment of the invention; 
         FIG. 2  is a schematic diagram of a blending system used to produce a product such as a soft drink that is formed of blended water and syrup according to the invention; 
         FIG. 3  is an isometric view of a mixing chamber incorporated in the blending system of  FIGS. 1 and 2 ; 
         FIG. 4  is a top view of the mixing chamber of  FIG. 3 ; 
         FIG. 5  is a section view of the mixing chamber taken along line  5 - 5  of  FIG. 4 ; 
         FIG. 6  is a section view of the mixing chamber taken along line  6 - 6  of  FIG. 4 ; 
         FIG. 7  is a section view of the mixing chamber illustrating the interaction between a first fluid and a counterinjected second fluid; and 
         FIG. 8  is a section view of a mixing chamber having multiple countercurrent injection nozzles according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  provides a general illustration of a blending system  10  according to one embodiment of the present invention. As shown in  FIG. 1 , a first liquid component is supplied from a source A, which may be a tank or reservoir (or alternatively may simply be a pipe that supplies the liquid component), and a second liquid component is supplied from a source B, which again may be a tank or reservoir (or alternatively may simply be a pipe that supplies the liquid component). The two liquid components are destined to be mixed or blended together to form a final, blended product. 
     From source A, the first liquid component is supplied through a line  12   a  to a metering pump  14   a , which is driven by a motor  16   a . Similarly, the second liquid component is supplied through a line  12   b  to a metering pump  14   b , which is driven by a motor  16   b . The metering pumps  14   a ,  14   b  function to accurately dispense desired quantities of the first and second liquid components according to a predetermined ratio. Representatively, the metering pumps  14   a ,  14   b  may be progressive cavity metering pumps, such as are available from any number of known manufacturers. The motors  16   a ,  16   b  that drive respective metering pumps  14   a ,  14   b  are preferably variable speed motors, e.g. servo-type motors. In a manner as is known, motors of this type can be carefully controlled so that the speed of operation can be constantly and almost instantaneously changed as desired, in response to input signals provided by a motor controller. In this manner, the operation of the metering pumps  14   a ,  14   b  can likewise be carefully controlled so that the output of each pump can be constantly and almost instantaneously varied as desired. 
     Metering pump  14   a  discharges to a line  18   a , and metering pump  14   b  discharges to a line  18   b . The lines  18   a  and  18   b  connect together at mixing chamber  20 . As will be described more fully below, the mixing chamber blends the first and second liquid components using countercurrent injection. The mixing chamber  20  is upstream of a static mixer  22  and functions to mix or blend the two liquid components together, as will be described. The mixed or blended liquid then passes through a mass flow meter  24  that is downstream of mixer  22 . In a manner as is known, the mass flow meter  24  may be a coriolis-type flow meter. 
     With the configuration as shown in  FIG. 1  and described above, certain characteristics or parameters of the mixed or blended liquid can be measured by the mass flow meter  24  at a point immediately downstream of the location at which the liquid components are mixed together, and then compared to predetermined characteristics or parameters. In the event the measured characteristics or parameters are determined to be outside of acceptable ranges, a controller responsive to inputs from the mass flow meter  24  can adjust the speed of operation of motor  16   a  and/or motor  16   b  to alter the supply of one or both of the liquid components from pump  14   a  and/or pump  14   b , to quickly bring the measured characteristics or parameters of the blended liquid within acceptable ranges. 
     The coriolis-type mass flow meter  24  functions to measure the volumetric flow, mass flow and density of the mixed or blended liquid. The flow volume is known from the output of the pumps  14   a  and  14   b , and the density of the mixed or blended liquid can be determined using the mass flow meter data. Many typical applications require that the liquid density fall within an acceptable range and the present invention allows precise and nearly instantaneous control of this important parameter. 
       FIG. 2  illustrates a representative application of the system shown in  FIG. 1 . In this application, the blending system  10  is used to produce a product such as a soft drink that is formed of blended water and syrup. It should be understood that the application illustrated in  FIG. 2  is representative of any number of different applications in which the system of  FIG. 1  may be used to blend two or more liquids together to provide a blended liquid having certain predetermined characteristics. 
     In the representative system shown in  FIG. 2 , the first liquid A is in the form of syrup that may be supplied from a syrup tank ST to pump  14   a . The second liquid B is in the form of water that may be supplied from a water tank WT to pump  14   b . The syrup and water streams are supplied through lines  18   a  and  18   b , respectively, to mixing chamber  20 , where the syrup is counter injected into the stream of water. Countercurrent injection of the syrup into the water stream provides improved dispersion of the syrup in the water stream. As a result, when the mixed fluid is presented to the static mixer  22 , the static mixer  22  provides more consistent blending. The mixed fluid then flows through the mass flow meter  24 . The flow meter  24  functions to measure the volumetric flow, mass flow and density of the mixed syrup and water, to ensure that the ratio of syrup to water in the mixed stream is within an acceptable range. In this manner, adjustments can quickly be made in the flow rate of either the syrup or the water in the event there are variations in the density (concentration) of the syrup, so that the density (concentration) of the final product is relatively constant. 
     As also shown in  FIG. 2 , carbon dioxide may be injected into the mixed syrup and water at a location downstream of flow meter  24  using a conventional carbon dioxide supply system shown generally at  26 . The carbonated liquid is then passed through a conventional chiller  28  and is supplied to a pressurized product holding tank  30 . In a manner as is known, the carbonated liquid is then supplied to a filler  32  which functions to dispense the liquid into individual containers  34 . An auxiliary booster pump and valve system  36  may be located between the holding tank  30  and the filler  32  in order to maintain a desired degree of pressure on the carbonated liquid during the filling operation. In an alternate embodiment, the carbon dioxide may be fed to the mixing chamber  20  via line  38  and preferably counter injected into the blended fluid. 
     In addition to pumps  14   a ,  14   b , check valves  40 ,  42  are placed in lines  18   a ,  18   b , respectively, to control the flow of syrup and liquid into the mixing chamber  20 . In addition to preventing back flow, the check valves  40 ,  42  also reduce leakage, particularly of the relatively heavy (dense) beverage syrup, into the mixing chamber  20 . 
     Referring now to  FIGS. 3 through 7 , in accordance with a preferred embodiment of the invention, the mixing chamber  20  has a generally cylindrical body  44  defined by an annular wall  46 , a water inlet  48  that is flow-coupled to line  18   b  such as by a clamp (not shown), a beverage syrup inlet  50  that is flow-coupled to line  18   a , such as by a clamp (not shown), and an outlet  52  that is flow-coupled to line  54  such as by a clamp (not shown), for example. The beverage syrup inlet  50  includes, or is otherwise flow-coupled to, a countercurrent injection nozzle  56  that is oriented to deliver the stream of beverage syrup into the stream of water. The countercurrent injection nozzle  56  has a nozzle body  57  defined by a generally annular wall  58  forming, in the orientation shown in  FIG. 4 , an upright portion  60 , a horizontal portion  62 , and an elbow portion  64  therebetween. The shape of the countercurrent injection nozzle body  56  is such that the fluid inlet  50  receives the beverage syrup along a velocity flow direction that is perpendicular to the velocity flow direction along which fluid exits the nozzle  56 . In one embodiment, inlet  48  passes water whereas the countercurrent injection nozzle  56  injects beverage syrup into the stream of water passed through inlet  48 . 
     As noted above, the flow of beverage syrup and liquid is controlled by respective check valves  40 ,  42 . As shown in  FIG. 4 , check valve  40  is oriented generally adjacent the discharge end of the countercurrent injection nozzle  56 . Check valve  42  is positioned in the inlet  48 . The check valves  40 ,  42  effectively control the flow of water and syrup into the internal volume or mixing volume  66  of the mixing chamber  20 . It is understood that the check valves  40 ,  42  can be of a known design. It should also be understood that other types of valve devices may be used to control the flow of fluid into the mixing volume  66 . 
     In one embodiment, the nozzle  56  is arranged such that its outlet  68  is centered about the velocity flow direction  70  along which fluid is presented to inlet  48 . An injection zone  72  is defined between the outlet  68  of the nozzle  56  and the inlet  48 . Fluid, e.g., beverage syrup, is expelled, i.e., “counterinjected”, through outlet  68 , once the check valve  40  is moved to an open position, and collides with fluid, e.g., water, that passes through the check valve  42  positioned at the inlet  50 . This collision generally occurs at the injection zone  72 . The force of the impact at the injection zone  72  causes turbulent flow of the mixed fluid components in the injection zone  72  such that the particles of the beverage syrup, S, disperse within the liquid, L, as illustrated in  FIGS. 6 and 7 . Additionally, the position of the nozzle  56  within the mixing volume  66  causes the mixed fluid  67  to pass between the exterior surface of the nozzle  56  and the inner wall of the mixing chamber  20  so that the mixing fluid  67  has a generally cone-shaped stream when it exists the mixing chamber  54 . 
     It is understood that particles of the beverage syrup are dispersed within the liquid in the aforementioned cone-shaped stream, but the fluids may not be sufficiently “mixed” to meet with various blending requirements. For example, in the case of mixing syrup and water, while the countercurrent injection of syrup into a stream of water will disperse the syrup within the stream of water, additional mixing or blending may be needed to provide an appropriately blended beverage. As such, the cone-shaped stream may be presented to the static diffuser or mixer  22 . 
     While additional blending or mixing of the cone-shaped stream may be needed, the countercurrent injection of the beverage syrup into a stream of liquid is believed to provide numerous advantages over conventional blending setups. For example, the present invention provides a substantially uniform or consistent distribution of the fluids. That is, there is not a significant separation of the beverage syrup from the liquid in the blended stream. The check valves provide relatively precise metering of the beverage syrup and the liquid, which is believed to reduce concentration spikes. Further, the use of check valves provides better control during periods of non-mixing. In conventional setups, as noted above, it is common for the heavier fluids to continue to fall into the mixing volume when the mixing process is stopped. This can result in a concentration slug that must be accounted for at resumption of the blending process, such as large averaging tanks, which the present invention does not require. 
     While the invention has been described with respect to the countercurrent injection of beverage syrup into a stream of water, the present invention may also be used for the countercurrent injection of water into a stream of beverage syrup. Thus, it will be appreciated that the invention could be used for the blending of first and second fluids wherein the second fluid is injected into a stream of the first fluid using a countercurrent injection nozzle to yield a cone-shaped blended stream. For example, the invention could be used to injected carbon dioxide, via the countercurrent injection nozzle  54 , into a stream of water to provide a stream of carbonated fluid. 
     As described above, in one embodiment, the invention provides a mixing chamber  20  that may be used to disperse a secondary fluid, e.g., beverage syrup, and a primary fluid, e.g., water. However, in accordance with another embodiment of the invention, multiple mixing chambers may be used to mix multiple secondary fluids with a primary fluid. For example, and referring to  FIG. 8 , an elongated mixing chamber  76  has a series of countercurrent injection nozzles  78  similar to injection nozzle  56  described above. Multiple mixing volumes  80  are defined along the length of the chamber  76 . Each mixing volume  80  is defined between a pair of check valves  82 , similar in construction and operation to check valve  42  described above. Each check valve  82  in effect defines the inlet into the next downstream mixing volume and the outlet for the preceding upstream mixing volume. 
     In the illustrated example, the mixing chamber  76  is designed to disperse four secondary fluids with a primary fluid. It is understood however that one or more of the secondary fluids may be the same fluid. It is also contemplated that one of the secondary fluids may have the same constituents of the primary fluid. In one example, the primary fluid (Ingredient A) may be filtered water, the first secondary fluid (Ingredient B) may be CO 2 , the second secondary fluid (Ingredient C) may be beverage syrup, the third secondary fluid (Ingredient D) may be CO 2 , and the fourth secondary fluid (Ingredient E) may be syrup. It will be appreciated that the above is just one example and that other mixing combinations may be used. In addition, for some applications, fewer than all of the countercurrent injection nozzles may be used. 
     The invention has been described with respect to a blending system designed to mix beverage syrup and carbonated water to form a blended soda that can be dispensed into a holding tank or similar container. However, it is understood that the invention may be used for blending beverages that are dispensed directly into a can, bottle, or similar container for later consumption. Additionally, it is understood that the invention could be used for blending of other fluids. For example, the invention could be used to blend water and gas to provide a liquid. In another example, the blending system may be used to blend a fluid, such as water, and one or more flavorings, so as to provide flavored water, flavored tea, and the like. Essentially, the invention may be used in any application in which two fluid components are to be mixed together. 
     Various modes of carrying out the invention are contemplated as being within the scope of the following claims, particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.